And another improvement of the server uptime record. I found a server (physical server) today that had an uptime of over 1550 days!
So it was powered on on thursday 18 june 2015. A long time ago!
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And another improvement of the server uptime record. I found a server (physical server) today that had an uptime of over 1550 days!
So it was powered on on thursday 18 june 2015. A long time ago!
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Today I encountered this server, which smashes my server uptime record:
10:51:44 up 1446 days, 18:24, 1 user, load average: 0.80, 0.85, 0.94
1446 days equals 14 days shy of 4 years!
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So, the inevitable has happened……….again.
I have bought myself another piece of studio equipment to live next to my Studer. I got myself an Otari MX-55N-M
This one I discovered in Belgium. Yes, down there. It came originally from a guy with a small studio who sold all his stuff, but I got it from someone who bought some records from that guy and got the Otari as a side catch.
Getting it from Belgium required a road trip. In about 2,5 hours we were there, it was actually not too far across the border. The place was a 2nd hand vinyl shop with a lot of records, but it had CD’s and DVD’s too. Oh, and comic-books, like Suske en Wiske.
The Otari was all dusty and just a little bit dirty, but not much. I brought a test tape that I had recorded with my Studer, as this is also a 2-track studio machine. I loaded the tape, plugged in my headphones and after fiddling with the knobs (how to put this thing in playback mode, and how to get signal from it) I got some sound from it and boy, did it sound good! Within a few minutes I knew that the sale was going to be made. I just had to do a quick check for any defects that I could find and if they would be a showstopper. I could not find any.
So then came the problem of transport. My car has a loading space with a flat floor that is 70 cm high and 100 cm wide. But the machine is with a cart and wheels and a meter bridge, as you can see from the pictures. We measured the Otari and thought: well, I may fit just laying on it’s back. And it did. So I didn’t have to dismantle the meterbridge or take the machine from the cart. That was good.
After we got home I cleaned it up. From beneath the layer of dust came a beautiful and almost pristine looking deck that has no marks on it of prior use. I started to play with it and explore it’s possibilities.
This is what I found so far. It came with a remote control with 10 meter cable, 2 Otari NAB adapters (which are very well built), and 2 aluminium reels.
I noticed that the left tape roller is making more noise than I would have liked, but it works ok and someday I will replace it. The heads are ok.
I am very fond of the smooth tape transport and the overall robustness of the machine. This Otari really is meant for heavy duty studio use.
I have not measured anything except for the fluxivity levels yet, but I expect the results like wow/flutter, distortion, frequency response etc. etc. will be very good. This will make a nice younger brother to the Studer.
Oh and by the way………..
I am looking for the manual, service manual and schematics for this MX-55 N-M.
I have found manuals for other models of the MX-55 family, but not specifically for the N-M.
I found some manuals online, but they only contained the first two chapters.
So, if anyone know of these manuals, either in printed or electronic form, I would be happy to get hold of one. Please leave a message in the comment section.
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Recently I got a Philips EL6021 mic:
It has the following specs:
Since the cable that came with it was unbalanced and noisy, making the mic rather useless, I decided to rewire the cable to make it balanced so I could connect it to my Mackie 24.8 mixer.
Some reverse engineering led to this diagram:
The connector can be fitted in each of three positions, giving the microphone 3 different impedances. See the side of the connector on the mic for the details.
It is absolutely noiseless now and it has a surprisingly good audio quality!
If you have any questions or remarks, please do not hesitate to ask me.
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This is the transistor list inside the PM2505:
In case you need to replace them 🙂
I replaced almost all of them in an effort to fix my multimeter. It did not function anymore. When I turned on the meter, the needle would go straight into the far right corner and do nothing, whatever the dial or switches setting.
After replacing the transistors and 2 caps that are on the board, I assembled it and when I wanted to test it I found out that one of the small metal balls that operate the function switch Volt-Ampère-Ohm had come loose and was freely inside the case. This is not good of course.
So I secured it in the correct place, the function switch is working as it should and the meter is also functioning perfectly! Happyhappyhappy!
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Just a quick post about my latest acquisition: an AGFA Bezugsband 9,5 DIN 45513.
Some pictures here:
I think it was made in 1967, which is a good construction year 🙂
I came with some documentation, which I will post here for reference and archival:
Also, much use is made of time constants like 3180 µs, which corresponds with 50 Hz.
The tape appears to be in very, very good condition.
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Sometimes, for instance when there is a sticker on top of the text that says whether it is a DCC90, DCC75 or DCC60, you have to guess the tape length.
Not anymore. I have created this diagram that show you just how long the tape is by looking at the casing (backside):
It is really silly, some brands (hello BASF!) mention the length of the tape only once on the casing, and that is exactly where normally a title sticker would be placed. By looking at the diagram, you will no longer have to guess. The black circles in the drawing are holes in the casing.
DCC90 would mean 45 minutes on side A, and 45 minutes on side B, totalling 90 minutes. In practice, there will always be a few extra minutes of tape in the cassette. This goes for all the formats.
DCC75 is a bit strange, it was also not used in normal analog compact cassettes, but it would gave you 2 times 37 1/2 minutes. Not quite sure what the reasoning behind that was.
DCC60 is 2 times 30 minutes.
Have fun with it!
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In the early 1980’s Dutch public radio featured a program called ‘Walhalla Symfonie’. It was described as ‘an acoustical listening trip’ (translation).
The program duration was one hour, broadcasted late in the evening. Only 34 (+4) were ever made. It basically was music, sounds, quotes, experiences etc. all put together into a one hour composition. It had a strong influence of electronic music. And every one of them had a theme. The series also had a leader tune, created on a synthesizer.
I remember some of them from my childhood. It was an exciting experience to listen in the dark (sunday evening 23:00) with your headphones on to this broadcast on the radio. Recently I found all of them on the internet, downloaded them and I again enjoyed listening to them. They have a unique atmosphere to them.
This triggered me to make one myself. So here is my attempt to make a Walhalla Symfonie!
It is much shorter, around 20 minutes. And it has a different feel than the originals had, mine is less experimental, less far out there, more mainstream. But I think that it is agreeable to listen to as a listening experience. So, if you have 20 minutes to spare, take a listen and let me know what you think! (quality headphones and a relaxed listening environment are strongly advised)
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I have lying around a box with +/- 50 used DCC tapes that I purchased a while ago. DCC is the Digital Compact Cassette, invented by Philips. I have gone through them all, I listened to some of the tracks on each tape and sorted which ones I wanted to keep because of what was recorded on it. But most of them could be recorded over.
In my youth I had the privilege to experience the evolution of the compact cassette (CC), also a Philips invention btw. It had just made its way from dictafoon-like devices to the hifi/consumer audio market. And I witnessed its rise to a high end audio device (Nakamichi et al.). I have lots of CC tapes, probably my entire youth is recorded on those.
Then, in 1992, DCC came. But by that time, I had lost interest in recording music, or audio as a whole for that matter. So I never really noticed at that time. Also the Sony Mini-disc and DAT recorders went completely past me.
But when I rediscovered my audio hobby around 2010, I got very interested in these three now obsolete recording techniques. And fortunately you can get these devices rather cheap these days.
I have all three devices now.
DCC surprised me in a very positive way. I got the same, familiar feeling playing cassettes that I had back then and that I had gotten used to. Also the deck that I got feels very solid and tape handling is direct. The DCC cassettes themselves feel very, very well thought about. Even the casing and the jewel box is outstanding well designed, even more so the prerecorded tapes.
On top of that, you get CD like audio quality. I say CD like, but I dare you to hear a difference. I was very, very impressed with the whole concept. In hindsight I wish I had used it back then.
I noticed when I went through the lot of old tapes however, that some of the DCC tapes were making a squeaking sound when they were played. And some of those would not play at all. The deck, just kept clicking, the drive mechanism reversing a few times, before finally giving up. So I thought that these were bad tapes, or maybe they had some shedding or sticky tape or whatever and that they could not be relied upon. I was resolved to throw them away.
It was clear that it was the tapes that were the problem and not the deck, because most of the tapes would play perfectly and the problem ones would not.
I did some research into cleaning the head of the deck, but found out that this was not a trivial task, and that the fragile head could easily get damaged. The general conclusion was that you don’t clean it, unless it is absolutely necessary because all tapes play bad and it is clearly visibly dirty. So I didn’t.
I researched some more and came across a post on a Dutch forum dedicated to Philips equipment. You can find the post here:
although I think you need to register first. And it is in dutch 🙂
It is described there that there are actually 2 problems: the squeaking and stuck tape. The squeaking problem is related to two pieces of felt that are inside the DCC cassette, not visible from the outside. There is also a third piece of felt, this is the familiar one that presses the tape on the head. The 2 problematic felts are located near the left and right rollers located inside the cassette:
These felt pads leave behind a greasy spot on the backside of the tape when the tape is not used for a long time. The deck has trouble running the tape past these spots and finally gives up. This spot is somewhat greasy, but also a bit sticky. This can be observed by pulling the tape somewhat from the cassette and checking the backside. It is not necessary to open the tape casing for this.
In order to do that, you must pull back the sliding cover and pull the tape out very, very gently with a small tool and make sure that you do not damage or crinkle the tape. You can see the gunk if you look very carefully. Let light shine on the surface. Make sure that the tape is at the problem spot when you stopped the deck and pulled the tape out, from BOTH reels.
It was impossible to make a good photo of this, so you will have to look for this yourself.
In order to clean the tape, make sure you gently use some non residu cleaner, like IPA or alcohol or videospray cleaner 90 or whatever fits you, and gently rub the problem spot using a cotton swab. Hold the tape down while you swab, careful not to damage or wrinkle the tape. That happens so easily! Remember it’s the backside of the tape.
After that, let the tape dry for a moment, simply wind the tape back inside the housing and play the tape. Voila! It’s working again!
For the squeaking problem: I fixed this by cleaning the felt located opposite the head as well. It won’t get completely clean, but just try to clean it as much as possible. I did it with a cotton swab with IPA. Just rub it a lot and also twist the cotton swab over the surface of the felt. Let the felt dry, this will take some minutes, and wind the take back inside.
After that, the squeaking was gone.
All info and the picture of the open DCC cassette are from the forum mentioned.
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Since I was very young I was intrigued by recording studios and the equipment therein. Can you tell?? (cue Studer A80 blog entry). A few years ago I had the opportunity to visit the famous Wisseloord studios here in Holland and needless to say that that was a thrilling experience. I am intrigued by the recording process, and mainly the tape part. But recording techniques in general have my interest. Like how to record a solo acoustic guitar, or how to record a symphonic orchestra. And as pure as possible. In order to do that, in the old days, you need a tape recorder, and there lies the base of my fascination.
Tape has a very nasty flaw: it introduces tape hiss into the signal. Tape hiss is clearly noticeable when you play around with consumer decks, giving a nasty hiss in quiet sections when you replay your recordings. This wasn’t so much of a problem when recording from LP or FM radio, which has a background noise that would make the tape hiss less noticeable. It became a bigger problem since CDs came around and the source of the recordings were becoming quieter or even dead silent.
If you wanted to minimize the tape hiss, you had to resort to quieter, and more expensive tape. You had to use the more high-end decks, and have them calibrated properly to that tape. Thorough maintenance became even more important.
If you thought that you had a problem with tape hiss at home, imagine the problem professional recording studios had with it. They have to conform to the very highest of standards because they are at the very beginning of the audio path, a path that would result eventually with you playing the record or CD at home. So they want to introduce as little noise (in general) to the signal as possible. Adding to the problem was the fact that multi-track recorders had 16, 24 or 32 tracks that all brought their hiss to the final 2 channel stereo end-mix.
Without proper noise reduction, even in the most expensive studio with the high end tapemachines and studiotape running at high speed the end result would suffer quite substantially from tape hiss.
To circumvent this problem, studios often reverted to using devices like noise gates. When the audio level of a track would drop below a certain level, the noise gate would kick in and mute the channel on playback. This was of course done so that the downmix to 2 tracks would be more silent in the quiet parts. There is an interesting article on the use of Kepexes used by Alan Parsons on Dark Side of the Moon by Pink Floyd:
I remember extensive use of Kepex noise gates. I think part of the sound is these Kepex gates. They had a certain sound rather similar to tape compression. We were not just using them to reduce tape noise, they had a sound as well.
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I like measuring. So I bought a National Distortion Meter. It is the VP-7701a.
This device is capable of measuring the distortion of an sine audio signal. And can be useful to calibrate vintage audio equipment.
To be able to make any meaningful measurements, I need to do some baselining, meaning that I want to measure the distortion when the device is not measuring anything at all. If that makes any sense to you. It does to me anyway 😀
When the base distortion levels are extremely low, I can measure devices and discard the base distortion. But when the base distortion levels are significant, then I would have to subtract these levels from the measurement each time I do a measurement. Which I do not want, because it is a hassle.
So in order to do that I need a pure sine wave for input. The device does not provide that, at least not one that is available to the user. The device measures the distortion by subtracting its own sine waveform from the one that is being measured, and the result should be zero. But only if the supplied waveform is 100% equal to the internal sine waveform. My search for a matching waveform therefor brought me to 3 sources:
This is the test CD that I once (’90-s) bought:
It has all kinds of tests on it: frequency sweep, fase checks etc and also sine wave tones across the audio spectrum.
This is the result of my base line tests:
The results show that both my soundcard and the commercial testCD are useless for my measurements. The CD that I made myself is a lot better. It performed marginally better on my Technics SL-P777than on my Philips DVD 963SA player (SACD). The result is such that I think that the base distortion is low enough to not take it into account when I start to measure real equipment. So I will be using this CD as my source for sine waves.
One side note: my CD is recorded at 0dB level, so the player outputs 2,5V which is rather high. I may have to make a second CD where the levels are lower, like -10 or -20 dB.
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To clean contacts in audio equipment, I do the following:
For potentiometers don’t use 60, this will erode the internals. Use Kontakt 390 or Kontakt Tuner(600). Tuner works very well.
Kontakt 390 is an old Philips recipe and should be an all-in-one solution. I have not used it yet.
Don’t use contactspray!
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A very good acquaintance gave me some recorders recently. Among them was this beauty: The AEG Magnetophon AW-2.
As you can see, this recorder is from 1951 and is more than 65 years old! This particular device that I have was used in cinemas for sound reproduction. It sits in a suitcase for easy carrying around. It is quite heavy though. It uses platters and pancakes.
It is in a very reasonable condition. So far nothing seems to be broken beyond repair. My goal is to try to restore it so that it plays tapes again. I have not turned it on yet, it first needs a lot of TLC.
It appears that when used with ‘modern’ tape, this unit will nowadays produce stunning results that would exceed what would have been achieved back then.
For instance, there are three very heavy duty belts in this one motor machine. And with belt I mean like belt from a car engine. They are not in a condition to be used again, so these will have to be replaced. Also some of the electronic components, like capacitors and rectifiers are way beyond their normal operating life so they will have to go too. And then everything else that I will run into. Hopefully the tubes, there are a few, still work.
I have started to open the device up and clean it.
There are of course a lot of electrical components as well that need to be replaced. The first and foremost candidates are the capacitors, as there are certain types that don’t last for so long.
The device contains some paper-oil capacitors, like this one:
This will certainly have to be replaced before I can switch it on. I am told that ones like this will probably be ok:
The device is really beautifully made. When I ventured inside I fell in love with it more and more. But there are a few ‘minor’ issues to be resolved, like: where is this supposed to be connected?
I was told that this rectifier could go up in (probably very nasty) smoke:
So I will need to figure out how to replace it.
Fortunately I have got the electrical diagram:
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I recently went on a road trip and came back with:
So now a have a total of 4 Philips N452X machines and that looks like this:
The two on the left with the white VU meters are the 2 track stereos, and the two on the right are the 4 track stereo machines.
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For some reason I got interested in the speed of my tape decks. Why, you ask? I really don’t know. I was fiddling around with my vintage Philips multimeter, which is capable of measuring the frequency of a tone, when I thought it would be cool to use that meter to measure the 1kHz tone which is a the beginning of my (generic) calibration tapes. If the tape runs too fast, the measured frequency would be over 1000Hz, and if the speed was too low, it would be under 1000Hz. Suddenly I was fascinated by the fact whether my decks were running at the exact speed or not, or if not, how much deviation it had.
Now, you have to understand that I do a lot (well, actually not that much) calibrations of decks, but I never ever calibrated the speed. I never bothered before. I never had a problem with speed before. I never had the need to adjust the speed of a deck. So whatever I measured now, it would be the ‘default’ speed, untouched.
So I loaded the test tape onto all of my decks, connected the multimeter, and did my measurements.
The results were sometimes surprising, sometimes more or less expected.
And a graph says more than words, so:
What can we conclude from this?
The Akai GX-77 really runs too slow
almost all decks run within +/- 0,5% of the correct speed, which is within the DIN norm
only 3 decks run a EXACT the correct speed: the Philips N4520, the Tascam 34B, and the Studer A80.
the Philips N4520 is know for its quartz/PLL like control, so this is no surprise
the Tascam 34B is a professional deck, but this result still surprised me
the Studer A80…..well…….need I say more?
So that has been a very interesting experience. But then I started thinking about variations of the speed, also known as ‘wow’ and ‘flutter’.
Wow is the slow variation in speed, with a period below 6 Hz.
Flutter is the fast change in speed, with a frequency above 6 Hz.
One can experience wow then playing a record where the hole is not centered, and the speed goes up and down all the time.
Flutter is more difficult to hear because it is so fast. It can be measured however. Flutter is created by faulty mechanics: a capstan here, a roller there, dirt, bearings, the overall construction etc. It would appear that less flutter makes for a more tight and clean sound.
There is always wow and flutter. No mechanical system is without them. It is just a matter of reducing it as much as possible.
what are the causes of W&F? There can be many. The capstan or axis involved might not be perfectly round. The bearing idem. The system may not be perfectly lubricated. There may be dirt on tape guides, causing jerky tape motion (on a microscopic scale). Tape may not be slit evenly. Etc. etc. etc. There really are too many to mention here.
Remember: There is always wow and flutter. No mechanical system is without it. Realize that.
Now there I had a problem. To measure W&F you need a special device called a ‘wow and flutter meter’. Of course, you can rely on Philips that they had such a product back in the days. They did. It is this one:
But unfortunately I don’t own one. It is on my wanted list though. They are relatively rare, and sometimes expensive. If you have one, or one like this, and you would like to sell it to me, please let me know.
What to do now? Fortunately I found an interesting program on the web that is supposed to measure W&F. It’s called WFGUI. Here is a screenshot of the program in action:
That looks impressive, right? It can measure DIN 45507, wow < 6Hz, and flutter >6Hz. According to the documentation provided with the program it has been tested against some real life hardware W&F meters and the results were very very comparable. Good!
Now I had a different challenge with this program, as it runs on windows, and I only have Linux. But, I soon found out that it runs perfectly fine in Wine! Yeah!
You can select between the 2 most used frequencies in calibration: 3000 and 3150 Hz. (It also shows the measured frequency for your convenience.) Then there are 3 values to take notice of:
Now, this is where it gets interesting. The program has different settings so it can measure different values. It can measure:
Now I will not go into too much detail here, but take it from me that the DIN norm is a sort of average between the 2nd and 3rd setting, i.e. it takes a little bit of both. If you want to know more, you can read the documentation that comes with the program, that has some nice graphs that show it all. That will explain everything. For my measurements I used all three settings (DIN, wow and flutter), and I measured all 3 values (RMS, Peak and Max RMS)
The problem I had is that measuring these kinds of W&F is traditionally done with a tone of either 3000 or 3150 Hz. And, more specifically, you need a special (and expensive) speed calibration tape with that tone on it recorded in a very precise manner.
Guess what, I do not own such a tape. They are quite rare actually, although you can still buy them at MRLtapes.com I presume. My regular Bezugsband (German for calibration tape) has a 1kHz tone at the beginning, but that is used foor reference level measurements.
So I thought about it a bit and I knew I was never going to buy that special speed calibration tape (>€130). What if I took my trusted tone generator and used that to record and immediately playback a 3kHz tone? Of course that would be an imperfect recording, because it would contain W&F, but wasn’t that just what I wanted to measure? And if you play back that recording on the same deck, doesn’t that give a good indication of the performance of that deck? The more I thought about it, the more sound (pun intended!) the idea seemed to be.
Doing that would mean that I could not refer to a know calibrated source anymore. But I’m not interested in those figures. I can now compare the performance of my decks between themselves, see who stands out, either way.
Some people may argue that one can not make his or her own test tape. Of course that is true. But that is not the purpose. I want to measure the W&F of a deck. I was going to use the deck itself to record a tone and play it back at the same time.
Some may argue that that is not a good way to measure W&F. I disagree. I will explain.
When you record the test tone on the DUT (device under test), it wil will be recorded with wow and flutter. That is clear. So it will be an imperfect recording. So what. That is what I want to measure, so that seems ok to me. Let’s assume that the recorded tone will contain at the maximum an amount of W&F of n. If you would examine the tape in a laboratory you would find max n W&F. The DUT obviously has a W&F value of n. So at some points in time the value would be 0 (zero), at some points in time the value would be n (the max value) and most of the times some value in between. This will vary constantly, and it will vary very quickly.
Now I play back this tape on that same deck that has that W&F reading of max n. So again, some of the time that tape will play back with no W&F, and some of the time it will play back with the maximum value of n, and most of the time some value in between. The resulting W&F will be 2*n at the most, to be exact that would occur when a piece of the tape that was recorded at that moment with n W&F value will be played back at a moment that the deck plays back with a W&F value of n.
So again I dragged all my decks to the test bench and hooked them up one by one. Now reading the values from the program proved to be quite a challenge, because the readings vary a lot and change very quickly. So i took a sort of ‘observed average’ , as I would call it.
I did the measurement all at 19 cm/s, because that is the common speed all my decks have. I have noted where I used an other speed, like 38 cm/s.
After a lot of testing I had a spreadsheet full of values that were very difficult to interpret. So I made a graph out of all the numbers and this is the end result:
This may seem overwhelming and confusing at first, but it really isn’t. Let me clarify for you.
Here are the conclusions:
There you have it. I hope you liked my article. If you have any comments, please leave them below.
-edit 31 may 2016-
I have recently purchased a ‘real’ wow and flutter meter, the B+K Precision wow and flutter meter 1035.
I have used this meter to check some results from the softwareprogram above, and the results fortunately match. Great!
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For some reason I wanted to do a recap job of my vintage quadraphonic amplifier, the JVC MCA-V7E that you see above. This unit is actually in very good shape, so the reason for me to do this is also unclear to me, really! But sometimes my ways are inscrutable.
A recap job means that you replace all the old, worn out electrolytic capacitors that are >40years old with new ones, preferably audio-grade types. Electrolytic capacitors are known to dry out when they get older. And then they lose their characteristics. Worst case is that they short out, or that they start acting as a coil or as a resistor. These are all things that you do not want in your amplifier. Or in any other device, for that matter. Also, the original caps were never the same quality as the ones that you can buy today just because manufacturing, tolerance and materials have become so much better in 40 years. So in theory this should enhance the performance of the unit.
Also, it is not a question if an electolytic caps will fail, but when. So after the recap your equipment will be good for at least another 40 years, but probably a whole lot longer.
If you are gonna do it, you want to do it good. Then you go for the audio-grade caps.
These black caps are available at sometimes crazy prices of several euros a piece, but there is a very good capacitor at a very reasonable price. So all audio enthousiasts like me that do not have a money tree in the backyard use these FC series caps, as you will probably need a good bunch of them. In this case I used around 50-60 of them, but I have not counted them exactly. I ordered them from farnell.nl they have the complete range of values at good prices. The only problem is the minimum order amount of 50 euros.
This is what the unit looked like before I started:
Basically all the grey capacitors that you see here had to be replaced. This consists of the Power Supply board, the tone/preamp board, the mainamp board, and the phono board which is located on the underside
I started with the PSU (power supply). These contained some big ones.
Note the difference in size. The new ones are a lot smaller. They have the same value nevertheless. After I had done the power supply, and the amplifier still worked (!!) 🙂 I tackled the phono board.
And then the preamp.
And then the main amp:
After all the works was done, it was time to turn the power on. Exiting! Nothing exploded and no component was getting very hot, so I connected an input signal on the four inputs and turned up the volume. Channel 3 was not working. Hmmm. I remembered a problem I had when removing the large capacitor from the third channel, when the copper strip had come loose from the board. On closer examination I saw that it indeed was not making contact properly anymore, so that was easily fixed. Now the 3rd channel worked ok!
The sound from the ‘new’ amplifier is very crisp, someone called it ‘clean’. I think that is an apt description. I turned the JVC up quite a bit, and experienced no problems. So I am very happy with that.
Next up is a bit of testing and especially measuring. Because I wanted to test some new type of transistors, I have installed them in the channel 2 pre-amp. I want to see how they stack up against the original ones. I am especially interested in distortion and overall performance. If they don’t perform well, I will re-install the old ones. Maybe the amp needs to be biased as well, but I’m not sure yet.
I also turned up the calibration on the meters quite a bit, so now the needles are showing signal even at normal volume levels, that was not so before. Previously they just lingered around in the left corner doing mostly nothing.
I have provided here a simple drawing of the electrolytics on both amplifier boards for your convenience, if you should decide to do the recapping as well. Good luck!
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Today I picked up a mint condition Akai GX-77
This photo is from the internet; I will upload a real photo later.
The unit does not work; the two pinch rollers won’t come down all the way and the tape loader roller in the middle is stuck at the top so I will have to fix that. The middle roller is necessary for tape loading and unloading.
This unit is a real beauty. It is an auto-reverse deck, and is capable of playback AND recording in both directions. Therefore it has 6 heads and two capstans. The capstans are always spinning, in opposite directions and only the pinch roller associated with the current playing direction is engaged. The result of this is that switching tape direction takes only 0,4 seconds.
Here are the full specs:
The first thing I did after opening up the unit was checking the belts. It has three: one capstan belt and two for the spooling motors. The capstan belt was ok, it was still feeling like it should, but it was probably a little stretched because it didn’t feel very tight to me. I ordered a new set which included the 2 spool motor belts for €12,-
Once I had the belts replaced, it still would not engage the middle roller. It is supposed to go up and down.
Searching on the internet I found that there is a large white gear wheel located behind the 2 flywheels which controls the up/down movement of the roller. When I manually engaged this wheel, everything worked. Tape was loading fine. But I had to help it every time. So what could cause this?
The answer is: old grease. Old grease is grease that, over the course of 35+ years, has started to dry out and instead of lubricating, it starts clogging things. So I had to take the unit further apart to the point where every gear wheel is removed and cleaned.
This plunger arm was very slow returning to it’s default position and probably missed the next turn when the hook had to engage. So I fixed that.
Also the right flywheel (as seen from the back) has a gear on it. This was also very loose on the spindle and could be turned quite easy. I put it in a ultrasonic bath and tried to clean it with IPA. Now it moves a lot rougher.
So after almost completely removing all moving parts and cleaning and re-lubing them I carefully put the unit back together to try a cautious test. Here is the result:
As you can see the unit works smoothly now. At the moment the deck is still mostly disassembled but I will put it back together again and then start the mechanical adjustments and followed by the electrical calibration.
As you can see the beauty is put together again and is recording and playing like new. Very happy with it!
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I possess one JVC 8-track player, the JVC ED-1240, a very nice and featureful deck.
The main reason I am interested into the 8-track world is, of course, the fact that aside from 4 track reel to reel tape, this is the only format that has discrete quadraphonic. I realise that the quality of the sound is not up to par like the Studer, or even a normal tape deck, but it will have to do 🙂
The first time I heard this 8-track deck i was very disappointed with the sound. So I found myself a challenge at hand. I have cleaned it, repaired it, refurbished the motor, changed the belt, demagnetized it, changed all the caps on the power board etc. etc. and eventually it performs quite well.
I cleaned and repadded the 8-track cassettes that I have. I even found it necessary to lube the inside axis a little bit to prevent squeaking and to lower the rumbling and the mechanical noises from the cassettes while playing. The end result is quite pleasing I must say.
But there are still some issues with the player, so if anyone has the schematics, or the service manual, please contact me!
But this post is not about this deck. The JVC is just stereo. This post is about a new one I just bought. A few weeks ago I ran, quite to my surprise, into a quadraphonic 8-track player from National Panasonic, the RS-845us.
Here it can be seen on top of my JVC. At the moment the picture was taken, it was playing a quad tape as you can see by the ‘4 channel’ indicator light. In this mode there are only 2 programs, not 4 as you would find with a stereo tape.
But, alas, this player also came with its problems. I tested it before I bought it, and it was ok as far as I could test it at the time. Coming home, when I could test it for a longer period, I found the same issues I had with the JVC, like irregular tape speed etc. Also the sound was not as good as I was used to from the JVC.
So I did my usual fixup things, like cleaning everything, oiling etc. No good. I quickly found out that the voltage over the motor was dropping several volts at times. I suspected the power circuit board. So i tested the diodes, they were ok. I tested the caps and replaced them all nevertheless, although they were not really out of spec. Unfortunately, that did not help much. New belt. There was some improvement, yes. But still the voltage drop at times, from 12-13V all the way down to 6-7V. The motor would almost stop turning then. And it would squeak a lot.
The solution would be to open up the motor and fix it there. That is always a bit tricky but I did it before and I therefore have some experience with the procedure. It went surprisingly well. There was some dust (powder) from the magnets and from carbon brushes. I also scraped clear the spaces between the 3 parts of the rotor (I think it’s called) so there would not be any more shortage. I reassembled a clean motor and lubricated it. When I tested it it it ran very smooth and silent. Cool! The tape speed is also a lot more constant than before. Also the sound seems to have some more punch to it. Maybe it has to do with improved tape-head contact, or with a more stable power supply to the audio board due to the changed caps.
But I also have the capacitors ready for a complete overhaul of the audio prints. So somewhere in the next few days I hope I will find time to replace them and see if that will fix the muffled sound. I don’t expect a lot from that action, but hey, that’s what this hobby is all about.
Yesterday I did the recapping of one of the 2 audioprints, i.e. the print for the front channels. This is the result:
When I tested the audio after the process, I found that there was very little, if any at all, change in sound quality. I had made a ‘before’ recording so I could compare the sound.
So I am a little disappointed about that, but I guess the 8-track format was never intended for good audio quality, At least I didn’t break it. 🙂
So while I have all the caps here to replace the rear print also, I will not do that; too much trouble for little or no result…..
Anyway the unit is reassembled now and it playing happily.
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So, the inevitable has happened.
I have bought a Studer A80-R.
This is a beast. The unit is 70x60x84 cm, and is the size of a washing machine. And it weighs around 100kg. That is even heavier than a washing machine. It has wheels though. So you can roll it around.
This is the studio recorder that the artists from the seventies used to record their material on. It came in several configurations, from 1/8” (cassette tape) to 2” (24 track). Mine is the A80-R (for ‘rundfunk’ i think) 1/4” 2 track, speeds 7½ and 15 IPS (19 & 38 cm/s). Every studio in the world had one, or several. The most prominent artists that used the Studer A80 are Pink Floyd, Alan Parsons, etc.
I came in contact with someone who has access to professional studio equipment and repairs them on a regular basis, often in his spare time. Sometimes studios get rid of these machines that are in the way, and then he takes them in and repairs and refurbishes them.
I have visited him to look at the machine that I would buy and the second time I went there, the machine was all done and I took it home. Which was not a simple task. It fitted the back of my car fortunately.
After I got it home I wheeled it inside, where it would stay in the living room for the time being. It was simply impossible to get it upstairs.
Here is a short clip:
The Studer gave me some challenges. First, the inputs and outputs are the balanced XLR type. I already have adapters to/from RCA which I used for my Revox PR99, but the problem is the line level. My other equipment is home use stuff, so it’s line level is -10dBV. The Studer, being a professional piece of equipment, uses +4dBu. This box fixes the level conversion and the physical connections.
Second, the Studer was simply too heavy to carry up the stairs to the first floor where my audio room is. So it sat in the living room, happily enjoying the family life. And, between you and me, it sounds so good in the room.
Unfortunately, after a few weeks, the left motor, the supply motor, was giving problems because the tension was not there in play. Also, rewind was not possible anymore. A search on the net and my supplier both revealed that on the board 1.080.383 there are 2 transistors that control the 2 motors.
They are BC141-16 with heatsink on them. On my deck the one for the supply (left) motor was broken. I replaced him twice, but that was not the cause of the problem. The problem was elsewhere. The transistor blows as a result of that other problem.
Further investigation revealed that there could be problems with the tension potmeters that control the tape tension (the A80 has a sophisticated tension control system) or with the motor capacitors that could be faulty after 30+ years. I tested the potentiometer and I could not find anything wrong with it. So I removed and tested all the motor caps (9 pcs.) and found they were not entirely up to spec anymore.
I replaced them all, and installed a new BC141 just tot be sure. And so far, it works flawlessly again. Fingers crossed.
So now that all the caps were replaced, i though that the tape tension was a bit off. So i grabbed the service manual and started the mechanical calibration of the deck. This involves setting the (emergency) brakes, the tape path, the capstan pinch roller, and of course the tape tension and edit mode characteristics back to the desired specification. I have bought spring scales just for this! It was fun to do and the end result is here:
So I had a Studer A80 in my living room. Now who can say that? It was always clear that it would have to be moved to the upstairs room eventually. When my brother-in-law heard about my problem, he thought it would be a challenge to get it upstairs. So one day he showed up on my doorstep. Long story short, an hour later it was done. Actually, it took almost an hour to do the preparations like attaching the rope appropriately (and carefully!), and it took just 10 seconds to go from the bottom of the stairs to the top of the stairs! So now it has reached its final destination, my “audio room”.
Being hooked up to some good sounding equipment, my trusty Technics amp and my new KEF Q700 speakers, and using my Philips SACD player as source, I made test recordings and played them back. My tape of choice was BASF 911 and SM900. The results were nothing short of spectacular! The level of OEMPF that his recorder is able to put on tape is astounding! And, those of you who are familiar with analog recording equipment will know that there is always noise (tape noise, vinyl groove noise, FM-noise, cassettes!) when working with these machines. Not so with the Studer! It is so quiet! And that is a piece of equipment that was made around 1970. Incredible.
I am still enjoying this beast. I am tempted to do the technical calibration as well to calibrate it for BASF 911 or 900, but it sounds so good already i’m not sure it would get much better, and there is always the risk of f***ing it up. So for now, i think I’m good.
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My new addition to the collection is already a few months old, but here is the blogpost anyway.
It is an AKAI 1730D-SS Quadraphonic tape deck that I received from the first owner.
[picture shamelessly stolen from the internet]
When picking it up I tested the deck and only 2 of the 4 channels worked. Only the REAR. Strange. And one of those 2 channels failed intermittently. When I got home I opened up the deck and had a look at it. I put on one of the many quadraphonic tapes that came with the deck. Quickly I found out that cleaning and fixing the 2ch-4ch switch solved that problem. That was easy.
But the FRONT channels still did not work. At all. No sound, no noise, no click when the deck was powered up, no nothing. I sure hope the playback amp hasn’t died. It appeared there are 4 audioprints in the machine, see picture. At the left of the picture you see the 2 playback prints, at the right the record prints. Each print is stereo. FRONT at the top, REAR at the bottom.
By turning the pot on the prints I found out wich print was unresponsive (I am going to recalibrate it anyway, so that did not matter). I took it out of its slot for further inspection.
Unfortunately I could not find anything wrong with the print or the components. No burned components, fused caps, burn marks, loose contacts, nothing. I was beginning to feel that I was reaching the end of my knowledge because I have not got expert knowledge of electronics.
When I was going to put the print back into its slot, I noticed something odd about the slot. The slot is a kind of very crude ISA-style slot type, like in the first IBM PC. I saw that the plastic of the slot was broken! That caused the print to not make good contact with the pins in the slot. See the pictures.
Now how to fix it. Glueing was no option. I soon thought of a tight tie-wrap, that might do the trick. I pulled the tie-wrap as tight as I could. See the pictures.
Then came the next issue. The deck did not want to record at all. I soon found out that the other slots were damaged too (duh). So another set of tie-wraps to the rescue. I put tie-wraps around everything and reconnected it all.
It worked ok, but not reliable. Even when just looking at the recorderprints weird effects on the signal were noticable. First I doubted my tie-wraps, but that solution DID work reliably at the playback prints. Just to be sure I sanded the contacts on the prints and voilá: everything worked flawlessly! So I put the print in and secured them thoroughly. ‘There, I fixed it again’
This is a machine from the early seventies, that has been idle for who knows how long, and I’m surprised at the audio quality.
Now I need to demag it, and calibrate it. Then it will probably sound even better!
Although it sounded good at first hearing, further test revealed there was noise in the left front channel ,even when it was not playing. Same on the right rear.
So I replaced the 2sc458 transistors on all the audio prints. After that, I eagerly turned on the machine.
No signal at all!
Remember that I am only doing this as a hobby, I am not a professional guy and I know very little about electronics.
Searching and searching and searching again I found out that the new transistors I had ordered, had a different pin-out than the ones that came of the print. I had put the new ones in with the same orientation as the old ones, that seemed logical but that was incorrect. They simply needed to be turned around, so that was relatively simple. I did not need to cross their legs.
After that it worked again, fortunately! Apparently these guys can withstand some rough handling haha. And the best part is, that the deck is silent again now, the noise is gone. I recalibrated it and it sound great!
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Recently I obtained, for a fair price, a Teac X-2000R. It is a stereo reverse deck, with 6 heads, which means it will record also in reverse. It has dbx built-in, and it can use (chromium) EE tape. A digital counter in hours, minutes and seconds and bias fine tuning on the front panel is also provided. It has 9,5 and 19 cm/s speeds.
Another prominent feature that is has, however proved to be a very problematic one. The deck is equipped with 2 capstans. This feature was introduced into the later tape deck models, almost towoards the end of the tapedeck-era, to further improve tape-head contact and wow&flutter. These assumptions are correct, and they work well when the deck is in new condition and everything is well calibrated and up to specifications.
On this deck however, things were not new and not up to specs. The dual capstan design is a challenge in itself, but things are further complicated by the fact that it has to function in reverse as well. On this unit that is accomplished by a belt that ‘travels’ across different parts of the flywheel that varies in diameter.
After the initial cleaning, optical and technical/mechanical, it soon became apparent that the tape handling was not up to par. Sometimes the tape would ‘run away’ from the heads a bit, resulting in loss of audio or worse: tape jam. Things were even worse when playing in reverse. I soon found out (through the service manual) that there were adjustments to be made to the tape tension.
But the increased tape tension was not the solution. When it was ok in forward play, it was bad in reverse. Or vice versa. Or it differed when loading large reels (26 cm) compared to 18 cm reels. Or it was different with different brands of tape. And that wasn’t even reproducible across sessions. And the next day it would be different again.
Of course the first thing I did was to change the belt. I have a blog of that action, but it is in dutch. So here it is, sorry only in dutch:
====== BEGIN OF DUTCH TEXT ======
Nou, de siem-snaar was snel binnen, en vanochtend was het toch regenachtig, dus aan de slag gegaan met het vervangen van de Teac X-2000R snaar.
Ik heb de uitbouw gedaan volgens de foto’s in deze thread, daar heb ik heel veel aan gehad:
Daar wordt behandeld een X-1000R, en die blijkt toch niet helemaal hetzelfde van binnen. Ik kwam meteen al een grote print tegen die in de weg zat, deze is er niet in een X-1000.
Hierdoor kon ik niet bij de bovenste schroeven komen van de plaat waar de capstanmotor op vast zit. De print moest dus los en daarna omhoog gelift worden, er zitten helaas te veel kabels aan vast om hem compleet uit de weg te krijgen.
Na wat kabelbomen losgeknipt te hebben, kon ik de print opbeuren en omhooghouden met een plakbandrol.
Hierna kon ik er wel goed bij.
Nog even de plaat losknippen van de motor zelf:
Er zitten alsnog wat kabels in de weg, maar die zitten gelukkig vast met connectoren. Loshalen die hap dus.
Eindelijk uitgebouwd. De 2 vliegwielen in de achtergrond:
De 2 vliegwielen verwijderen. Goed links en rechts uit elkaar houden.
Overigens viel me meteen op het grote verschil tussen de snaren: de oude is een stuk langer dan de nieuwe. Dus of de oude was wat uitgerekt, ondanks dat het rubber nog vers aanvoelde, of de nieuwe is ietsje te krap. Of allebei.
Toen heb ik alles losgehaald en schoongemaakt en opnieuw gesmeerd: de vliegwielen, de aandrukrollen en het aandruk mechanisme. Oud vet verwijderd, nieuw vet er op.
Alles zeer grondig schoongemaakt. Vliegwielen er weer op, meteen de washers aan de voorkant weer over de capstans gedaan. Nieuwe snaar er op:
En toen alles in omgekeerde volgorde weer vast. Het was een beetje pielen om de snaar weer over de motor te krijgen, maar het ging uiteindelijk wel. Als laatste de print weer laten zakken en vastgezet.
====== END OF DUTCH TEXT ======
Unfortunately this was not the solution that fixed it completely, although the situation improved a bit. Even increasing the tape tension to incredible heights (or incredible lows) did not fix it. So I went online to find a solution.
Several fora messages suggested that everything in the tape path was relevant to my problem. From tape guides, to the rubber idle rollers, to lubrication of the tension rollers, to the state of the rubber of the pinch rollers. From the tape tension to the smoothness of the tape in question. It seems that everything was related to weather the dual capstan principle would function correctly.
So I soaked the pinch rollers in detergent for one night. The rubber was much softer and grippier after that treatment. Again, a little improvement, but no permanent fix.
I switched the pinch rollers from left to right, to see if that would improve the situation. No way.
I lubricated all the moving parts, I installed the little O-rings that were required for the rollers to function correctly (expensive little buggers!). Still there was no definitive solution that worked all the time.
In April I went to a meeting of fellow tape deck enthusiasts where there was an opportunity to work on decks. I tagged the deck along, and fortunately there was an expert who was willing to take a look at the Teac. Immediately he found one problem: I had put the tape tension way too high. We measured more than 100 gr. when 50 was required. He used a Tentelometer, a very rare instrument which he posesses. It looks like this:
After we adjusted the tension to 50 grams, the tape handling was still not good. In fact, it was worse. Then, the guy helping me thought the problem might be in the capstan motor, of which the carbon brushes would have degraded over the years resulting in less powerful drive. So, on the fly he opened the capstan motor, removed the old brushes and (he had them available) installed new ones. After this, still no good. But I had new carbon brushes! Jeey!
At the meeting we came to the conclusion that maybe the new belt I had put in was not an original Teac spare part but a fake. So I went to an official Teac repair center and got myself an original Teac approved belt. After I installed that belt, still not any better. Grrrr.
Eventually, as a sort of last resort, I took the Service Manual and went through all the mechanical adjustments mentioned there. Some I could do, some I couldn’t. For instance, I haven’t got a spring scale necessary to measure torque. And then, finally, after I adjusted the pinch roller pressure to a much lower value, it suddenly all seemed to come together.
When I adjusted for a very, very low pressure of the pinch rollers on the capstans, even to the extend that I could very easily stop the tape when playing, the tape would indeed run fine along the heads and reverse play was no problem. So I adjusted for a little more pressure but anyway now it works great and I haven’t got any more tape issues.
After that, I planned to calibrate the deck. This also proved to be not as easy as I thought. The service manual mentions a lot of steps and I think I did them all 4 or 5 times. The problem was that the record calibration required EE or Chrome tape, which I did not have. Fortunately I could borrow a Maxell XLII tape from a friend.
Bu after I calibrated the deck using the EE tape, it did not sound good. The level was way too low. And when I recorded at a higher level, the amount of distortion was unbearable. Something was not right here. After advice given to me on my favorite forum, I used normal tape to do the calibration. It still wasn’t to my expectation. I’m not sure what fixed it, but I repeated the calibration procedure several times, and after that I found the recording to be very good!
So the deck was performing as it should, reversing as it should, handling tape as it should and now I was to test it with EE tape and with the dbx noise reduction and dynamic expander on.
The result was, well, as close tot the original sound as you can hope for. The high tones were beautiful, and the sound was quiet as a CD. Out of nowhere the music starts. This is tape technology at it’s finest. I am very happy with my new tape deck.
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Yesterday I received my new cartridge: the Ortofon 2m red. It came with a brush, some screws and a little screwdriver. All in the package for €84,-
I had read a lot about installing and adjusting phono cartridges in the past few weeks so I understood the basics. I had downloaded the Technics protractor from vinylengine.com, printed it and checked the scale of the print. But now it was time to put the theory into practice.
I soon realized that this new cartridge wouldn’t fit in the headshell I had designated for it. This is an old style Technics head shell with one screw on the top.
Although only one screw is visible in the picture, it has an additional mounting bracket underneath that should fit the 2 screws necessary to mount normal cartridges. But my Ortofon needs to have the heads of the screws on the topside and that is not supported in this headshell.
But fortunately I have two headshells, the other one is the newer type which has the normal two screwholes at the top. Using the screws which were provided in the package I was able to quickly attach the cartridge provisionally to the headshell.
So that was fairly easy. Next was the task of adjusting the ‘contraption’ 😀 I took my protractor and put it on the turntable on top of a record.
I soon learned that when I moved the cartridge all the way to the front of the shell that the needle followed the ‘arc’ on the protractor perfectly. Yes!
But when I tested the alignment of the cartridge on the two gridline patterns on the protractor, I found that it was not perfect in line. So I adjusted it very slightly to the point that it was in line on both patterns and then secured the screws. Pfew! Job done!
Then came the testing. I must admit I was a little but afraid, or better anxious. I tried it out with a record from Yes – 90125.
I put the needle down very very carefully.
I put on my headphones.
But as soon as the first tones from the song (Owner Of A Lonely Heart) were played, I relaxed. It sounded very very good!
There is a lot of definition in the sound. There is also a lot of ‘punch’, which I like. HF tones are also ok. Bass is tight and well defined. Overall, I have never ever heard a record sound so clear. True, in the past I have not had good quality turntables. In fact, they were rubbish. But I never thought a record could sound like this. It is so close to a CD. I’m also very glad that I treated my records carefully in the past, I didn’t play them a lot (I immediately recorded them onto tape) so that I now have old, but ‘like new’ records that sound wonderful!
I continued to listen to albums from ELO, Marillion, Tchaikovsky and 12-inch’s from Chaka Khan, Unique (What I Got IS What You Need). Those were the first records I found for grabs. It was a good experience. I am pleased. In the coming evenings I will listen to some other albums.
I was surprised how quickly and how easily an inexperienced person like myself could do this task. It took me a little over an hour including the adjustments. I can recommend it to everyone.
Coming up next: cleaning the records with a LP cleaner
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This week I picked up a Technics SL-1900 turntable
I was actually looking for a more high end model, like the Technics SL-1600Mk2, SL-1700Mk2, 1800Mk2 or even an SL-5300. But, those are hard to find, and when found, are very expensive and could cost more than €200,-. I found a very inexpensive SL-1900. It still had the original Technics 270 cartridge installed. And it came with an additional 270 cartridge without a needle. So I thought ‘oh, what the heck’, and I went to get it.
I was not disappointed. Not at all. In fact, I was very impressed. For the last years I have used a Dual cs-607, so that was my reference. And although the Dual has more definition, this one is more agreeable to listen to because….well, it has less definition. It doesn’t reveal all the noises and scratches and clicks and pops from the record so much as the Dual does. Compared to the Dual it lacks highs though.
Please read the next post on how I installed an Ortofon Red cartridge in this turntable. https://www.reeltoreel.nl/blog/?p=364
Some information from internet:
The Technics SL-1900 is a 2-speed, direct-drive turntable with fully automatic single disc playback. A one-chip IC, incorporating 321 elements, controls motor speed for superb accuracy with servo control. The tonearm mechanism gives convenient automatic set-down, lift-off and stop. Memo-repeat control permits up to six repeated plays of the record, or continuous play. The heavy monolithic bas and isolator system protects against external vibrations. The SL-1900 comes complete with an EPC-270C-II moving magnet phono cartridge.
und auf Deutsch:
Information about the cartidge:
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The other day I received two dbx encoded 7″ singles, demonstration discs by Technics. These are supposed to have superior dynamic range and almost no noise/hiss/rumble whatsoever.
First some background:
dbx was also used on vinyl records, from 1973 until around 1982, and over 1100 albums were released with dbx encoding, which were known as dbx discs. When employed on LPs, the dbx Type-II system reduced the audibility of dust and scratches, reducing them to tiny pops and clicks (if they were audible at all) and also completely eliminated record surface noise. dbx encoded LPs had, in theory, a dynamic range of up to 120db. In addition, dbx LPs were produced from only the original master tapes, with no copies being used, and pressed only on heavy, virgin vinyl. Most were released in limited quantities with premium pricing. [wikipedia][
Well, the accompanying sheet suggest that you hook your equipment up to a dbx capable (cassette) deck, but I didn’t. Instead, I connected my dbx model 150 unit. Better!
On all 4 sides was music, mostly jazz-like. On side A of the first disc was an impressive dynamic piece with flute and big drums. I was very surprised when the drums reached full power! And they go very loud! It is an extremely dynamic experience. Even on headphones.
Clicks and pops and other vinyl noise are so unnoticeable, the whole listening experience is very, very enjoyable. Even the dropping of the needle was hardly audible. Now, I need to find me some other dbx encoded discs!
edit: while writing this down, I’m thinking about what would happen if I record this on a tapedeck with dbx encoding.
Or better: skip the decode and encode step, and record the disc as-it-is on tape, and the play it back through my dbx unit….interesting experiment. I should try that some time.
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A few months after my purchase of the Philips N4520 tapedeck, it developed a nasty fault: during playback there would be cracking sounds coming through the music, or even when not playing at all. Also when touching the knobs, there would be pops and clicks.
An intensive internet search revealed that there were more decks affected with the same symptom. Fortunately, a remedy was also given: replace the transistors on the main circuit board with new ones. Gulp. All 19 of them.
I have some experience with soldering, but this was a completely new level for me. I happen to be in possession of a very good soldering station with temperature control, and I have used litz wire once or twice, to remove solder of the component you want to remove.
7x BF245A : TS2 TS5/TS105 TS4/TS104 TS3/TS103 1x BC547 : TS11 4x BC548 : TS8 / TS108 TS9 / TS109 2x BC549 : TS1/101 1x BC557 : TS10 2x BC546A : TS6/106 2x BC556A : TS7/107
Total number of transistors: 19 pcs.
Total cost: around € 10,- excl. transport.
Then, the scary part started.
Taking apart the biggest monster in taperecorders known to mankind.
Well, almost. And, as I found out, the bottom part slides out fairly easy to the front. And it is connected to the rest of the machine with connectors. So in the end you have the bottom part which contains the ‘mainboard’ as I call it as a separate unit on your workbench.
Locating the components on the printboard was difficult, but doable. Then soldering started. Using the litze wire to remove the solder from the board, I was able to remove the components.
Working methodically through all components, I replaced all 19 of them. Double-checked the joints for good contact. Cut away the excess pins. And I was left with this:Then it was time to test. To do that, the mainboard had to be reinserted into the recorder and reconnected.
It worked! Yeaj! I now have a N4520 that plays back and records beautifully! It took about an afternoon’s work and about ten euro’s, but Then you have successfully restored a very very nice machine.
See a video of this beast in action on my YouTube channel: http://youtu.be/UTS9aYsIH2k
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Yesterday I finally got my brand new Sennheiser HD-600 headphones. They look amazing, but they sound incredible!
I can really recommend these to any audiofile out there!
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