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.

IMG_20131101_171351IMG_20131101_171428So, I ordered the necessary components on-line:

 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

My new friends

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.


Don’t shake!


My old friends. Well, not my friends anymore!

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.


The glorious Philips N4520 in action 

See a video of this beast in action on my YouTube channel:  http://youtu.be/UTS9aYsIH2k

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Servicing the new ReVox PR99 with new VU lamps and roller bearing

Hello all,

Today I have been busy servicing my new ReVox PR99. This deck is built like a tank (to use an too often heard metaphor regarding tape decks) and it is working well. It is a 2 track deck which is designed for heavy use, like in studios and broadcast facilities. It is world famous for that.

But when I received it – actually I fetched it from way across Holland – I immediately noticed three small things wrong with it:

  • the VU meter lights were not working
  • the left tape guide roller bearing was making noise
  • and the infrared tape sensor incorrectly identified tape as being leader tape and switches off. This happens with some tapes that are apparently too thin 🙂

So I ordered and received 2 spare bulbs (from a webshop) and one new roller bearing (from ebay Germany) and opened the unit up.


rear view



P1020841 P1020842 P1020843 P1020844 P1020845 P1020846 P1020847 P1020848 P1020849 P1020850



without case







First I removed the siderails and the frontplate knobs




Then I removed the face plate all together.






Get the meters and the controls out





Remove old and insert new bulb





Testing….yes! Part 1 is done!





Remove the bits around the heads.
Also a good time to do some cleaning.





Remove the old roller bearing





And put the new one in place. Part 2 done!






Also put the unit on 240 Volts






This is the test point where the tape sensor should be measured





And this is the potentiometer that should be adjusted.






All done! There is light in the dark!

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New arrivals: Philips N4520 & Teac X-300

New decks

All of a sudden the tape recorders are pouring in. At almost the same time I got hold of a Teac X-300, a small 18 cm reel deck from one of the last series made by Teac around 1987, and a Philips N4520 from around 1978, which is THE kick-ass deck to have from Philips if you want to do serious business. It is really monstrous.

Philips N4520

The Philips N4520 has some unique features not found on other decks or only on very expensive studio decks, like

  • bias adjustable from the front panel
  • wind speed is adjustable on the front panel
  • electronic tape counter in 1/10 meters
  • Selectable equalization (at 38 cm/s) after NAB or IEC
  • cue buttons for fast winding&play without using the stop button
  • peak hold (yes, on analog VU meters!!) with peak leds as well
  • mini input mixing console with master fader
  • constant tape tension, so no reel size switch needed. Even when winding!


After listening to my first test recording on the 4520 with new and fresh SM911 tape through my Sennheiser HD-600 I was really blown away by the depth of the sound! It appears the 4520 has a build-in headphone amplifier that is very very good! It adds a lot of OEMPF to the sound. I did not know a good phone-amp was that that important to the overall sound. Also the sound quality on the line level is astonishing. The only difference when comparing the recording to the original is the tape noise, which is by the way very low. But that can be solved by using my newly bought (I haven’t told you yet. Sorry about that) DBX units.


Anyway, this Philips is the top of the line from all Philips tape decks. Among audio enthusiasts it is a very sought after model. It has some weaknesses, but mine has been under repair and is now ready for use. Also some modifications only found on later produced machines have been done. Sonically, I think it is my best sounding machine. But a comparison between my Tascam 34B and this baby will probably happen in the not so near future.

Teac X-300

Not forgetting the other new deck, the Teac X-300. It is a compact built unit, as it only carries 18 cm reels. It is one of the last series built by Teac, and it shows. It has a plastic look and feel, however, when you operate it it feels very robust. It is capable of handling the new EE tapes (or chrome) with superior audio characteristics which unfortunately have not been very successful when they came out in the mid 80-s. I do not own such a tape, so I can not test it.

This unit came very cheap, only €50. It is in e very new state. I don’t think it has many hours on it. Everything on the deck feels new and fresh, like the brakes and the controls etc. When comparing the sound quality using SM911 with the new N4520 it came sooo close, I was really surprised. This is definitely a keeper, if I can live with the small reel limitation.

Tomorrow I will add some photos to this article

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Some simple math…..proving 0,999999999 equals 1

I am going to prove to you, using standard algebra, that

0,99999999999….. equals 1.

Now I know that if you have even a basic understanding of maths you say: ‘I know for sure that’s not true’, but I will show you otherwise.

So here is the breakdown:

    1. let’s start by substituting 0,99999999999….. with the letter a, so

a = 0,99999999999….. 

That is easy huh?

 2. now say 10 times a would mean

10a = 9,99999999999…..

that is still right, right? I don’t believe that there is any need for discussion here.

3. if we substract a from that, of course you have to do that on both sides of the equal sign, we get:

10a – a = 9,99999999999…..  – a

still a correct formula.

4. 10a – a is of course 9a, so:

9a = 9,99999999999…..  – a

 5. but since a = 0,99999999999 the right side of the formula could be written as 9

9a = 9

6. and that means that a must be 1

a = 1

7. combining step 1 and step 6 I have proven to you that

0,9999999999….. = 1

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The surprising Teac A-3340S

From a friend of mine I recently received a Teac A-3340S in good condition. Here is a picture of it:


Teac A-3340S in good condition

My friend had just acquired it and asked me to take a look at the levels and to do an overall adjustment of the deck for him. This is I believe the first 4-track quadro deck by Teac, introduced in 1973. The deck is very very heavy and very very well built. This particular deck is also very well kept, there are no signs of usage and it looks like it has just come out of the shop. Remarkable as this deck was in production from 1973 until 1978.

IMG_20130802_090704 IMG_20130802_090722












After I serviced it, it sounded wonderful! It was a pity I had to return it to my friend, but well, it was his deck.

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I found a fine new tapedeck: Philips N7300

A few weeks ago I found an interesting tape deck online. It was a deck from Philips. It was close by so I immediately e-mailed the seller and after some conversation I fetched it with the car. It was a good price. Although Philips are not well known for the quality of their consumer decks (whereas their professional decks ARE good) I was interested because this was their last model that they made before production stopped because of the changed market conditions, everyone wanted a cassettedeck.

I believe it was produced in 1983, so it is fairly modern in its technique. It has controlled tape tension amongst other things.3 speed: 4,75 & 9,5 & 19 cm/s. It takes the BIG reels. Pitch control.

P1020407The problem with this deck is that it is entirely made of plastic. And I mean not just the front and the chassis, but even the cog wheels and everything inside. The result is that it is very light, especially compared to some of my Teacs and Tascams. So far nothing has broken. This would be a big problem as it seems to happen a lot and the plastic parts are, well, impossible to find or replace. Fingers crossed! The only thing that didn’t work was the on/off switch, but I managed to secure it in the ‘on’ position and I just unplug the unit to switch it off. Works for me!

Philips N7300 with tone generator

Philips N7300 with tone generator

So, after the holidays I managed to find time to do my adjusting and tuning. The Service Manual was quickly found on the net and then I started work. Unfortunately the SM is, well somewhat vague in some parts. It was quite the struggle I must confess. I could put my new oscilloscope (also from Philips BTW!) to good use. In the process I found out I still need to learn to use the scope better. But I managed.

I just finished the work recently and did some tests with test signals and some music. I must say that the results are very, very good. Did I mention that this is a very good sounding deck? Switching between source and tape it is very hard to hear any difference at all. I use new BASF LPR35 tape. Especially at the middle speed of 9,5 cm/s it performs remarkably, delivering very close to the same audio quality as at the highest speed. I was really surprised.

Even at the slow speed, at 4,75 cm/s it was very acceptable. One could use that for parties where the music will not be played loud, for background use. A full reel 26 cm with 35 micrometer tape has 1100 meters on it, giving a playing time of almost 6 1/2 hours! Using the thinner tripleplay tape of 25 micrometer gives even longer playing time of 8 1/2 hours.

Overall I am very pleased with it. This will probably become my main deck for 4 track stereo recordings, where the TASCAM 34B is the main deck for 4 track quad recording.

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English text follows below:

Hier een filmpje van onze huiskoolmezen. Eigenlijk zijn het geen echte koolmezen, maar een andere mezensoort. Welke dat is, dat weten we niet 🙁 Ze hebben een kuifje….

Sinds enkele weken hebben we jonkies in ons vogelhuisje. Op dit moment staan ze op het punt van uitvliegen. Ik heb hiervan een filmpje:

English text:

This is a clip of our domestic tomtits. They’ve got a tuft….

For some weeks now they are in our birdhouse. At the moment they are on the verge of fledging. I have got a clip of this:


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Another server uptime record!!

The last uptime record of one of my servers was around 300 days. Today I found that the server still hasn’t rebooted and that has even more uptime: 353 days. Another new record!!

The screendump is as follows:

fotoserver:~ # uptime
 08:35am up 353 days 16:55, 1 user, load average: 0.14, 0.05, 0.06

(view count: 388)

New project: Sony TC-378

Sony TC-378

Sony TC-378

This is my new project, the Sony TC-378. This is the ’tilted’ tape recorder, the front plate is hanging back, although is is not very visible in the pictures. The message given to me when I got it was that it worked ok and the pause button was missing.

Well that is both true. It plays nice and the pause button is indeed missing. It is possible to use the pause function however. This unit has the nice feature of a pinch roller that is moving out of the way when the tape is not playing. That is very clever because the tape path is clear when loading the tape. No fiddling the tape in between the capstan and the pinch roller. How this construction will last over the years is of course another question. And pinch roller pressure is of course also an issue.

TC-378 open

TC-378 expanded

The only thing that is in need of fixing at the moment is the supply reel. When rewinding, it makes a screaming sound that is impossible to bear. I guess there is something wrong with the bearings. I will have to look into that.

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Finally calibrated my Tascam 34B

Teac A-3440

The ‘older’ Teac A-3440


This past week I finally got round to working with my recently bought Tascam 34B. Ever since I got it a few months ago, I haven’t been satisfied with the sound at all. And surely not for this kind of machine. The tape transports are ok, very good exactly. The overall look and feel is excellent, working with it is an absolute joy.

But the sound was not ok. The sound was a little bit muffled, and some highs were absent. My older Teac A-3440 sounds a lot better. But of course, that deck I have already tackled. Using some other decks I finetuned my skills over the last few months, and now I felt the time was right to take on the big mighty TASCAM 34B.

Fortunately I had the service manual (recently purchased on the internet for a few euros, it was not freely available) so I used that as a guide. Other tools I used were my trusty calibration tape, a blank tape of LPR35, my old Philips scope (which will be replaced by a better scope, more on that later), my Philips analogue voltmeter PM2505, and software called Visual Analyser (for spectrum).

On the workbench, my 34B looked like this:


TASCAM 34B with face plate removed


TASCAM 34B bottom view. Notice the adjustment ‘knobs’

So, after a lot of fiddling with the potentiometers, measuring levels, changing tapes, etc. etc. I was done. So I eagerly recorded my first music onto it, played it back and …………..


The sound was really, really great! I used CD recordings of Dire Straits, Donald Fagen, and 4-track surround (quad) music of Pink Floyd, The Doors, Doobie Brothers and Queen – Bohemian Rhapsody to test, and I could hardly, if at all, distinguish between de CD and the tape.

This is truly amazing. I did not know a tape recorder could reproduce sound this good. As you can notice, I’m happy with the modifications I have done.
I don’t think this baby will go anywhere anytime soon, it will stay with me.
tascam 34b small

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Server uptime record

Today I noticed a new uptime record on one of my servers. The screenshot follows:

Have a lot of fun...
fotoserver:~ # uptime
 09:17am up 301 days 17:39, 1 user, load average: 0.00, 0.01, 0.05
fotoserver:~ #

301 days, a new record for a server.

(view count: 326)

Uptime record for workstation

Tomorrow I am going to reboot my workstation. So, before that happens I’m going to post  the screenshot with the new record uptime here:


openSUSE 12.1 with uptime of 223 days


Just as I was taking the screenshot, the uptime flipped to 223 days. A New Record!

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A New Finding

I recently found an old, but rather unused Akai 4000DS Mark 2.

Akai 4000DS Mk II

My Akai 4000DS Mk II, head cover removed, here in play mode

I got it for 25 euros from a first owner, who clearly was careful with his equipment. The only thing it suffered from, was a lack of maintenance and the fact that it had been sitting idle for a long time. I got it with one old and worn tape. This tape contains mostly 70-s music, like Abba and Steelers Wheel.

I really wanted to start working on Akai decks, because here in Holland, there are a lot of Akai reel-to-reel decks sold in the past decades. And I mean A LOT. I guess that for every 2 decks, one is an Akai. You see them everywhere. So, while it is not my favourite brand (that would be Teac/Tascam) in the future I will encounter them a lot and this will be a learning experience, and I wanted to get some hands-on.
This deck is a budget deck from Akai, so I can really try things out without the risk of messing up a more expensive deck. I will try that later on :). I already downloaded the servicemanual for this device, so that will be my guide during the repair and calibration process. My goal will be to fix this deck up so that it will perform like new, functioning to the best of it’s abilities.

The quality is well, let’s say, not entirely up to standard. Although the unit is fairly clean overall, the heads were covered in a lot of dirt. Unfortunately I haven’t got a picture of that. I was wondering at that moment if I would ever get them clean again, or whether it may be corrosion and thus irreparable  besides fitting in new heads.
I cleaned the heads and the entire tapepath with 96% denaturated alcohol. Then I tried to make a recording. That worked, and listening to it using ‘source – tape’ switch it sounded remarkably good! This was promising. I noticed that the odd ‘equalizer 3 3/4 – 7 1/2’ switch really does make a difference: when set on 3 3/4 (inch/sec) the audio contains too much high frequencies.
Another fun fact about this deck is that there is no speed switch: to make the deck run at the higher 7,5ips/19cm speed, you have to use an add-on to the capstan, that is stored on a storage post on the faceplate above the heads. Here’s a picture to make it clearer:

capstan with on the left above the head box the additional piece that goes over it.

When applied, the capstan is thicker and the tape runs at the higher speed. The capstan motor never changes speed!

Next, set the deck to 240V, the new line voltage here. As the deck only has one motor for all tape transports like play, fast forward and rewind, there’s a lot of mechanics going on inside. Greased that all up. Demagnitised the heads and tape path. Cleaned that with IPA too, and the rubbers also. The deck runs smoothly now.
A test recording confirms the new found audio quality. Then, loaded a calibration tape and adjusted the playback head’s azimuth with the 1 & 10 KHz tone using a scope. Here is a picture of what that looks like:

Akai 4000DS 10 KHz azimuth

Akai 4000DS 10 KHz azimuth

After that, made a picture of my trusty scope while playing back an 18 KHz tone from the calibration tape:

18 KHz toon vanaf referentieband op Akai 4000DS

18 KHz tone refererence tape Akai 4000DS

That’s not wrong at all. So far, so good. Next up is the further calibration of the electronics on this deck and calibrate it to use the newer 320 nWb/m tapes, but the service manual is a bit, well, let’s say, unclear about some things.


Well, I have gone further with this deck. I could not figure out some parts of the Service Manual (I think it may be a bit incomplete or in error, but anyway who am I) so I finished it of with adjusting it as best as I could. And I must say, it sounds far better then I expected from such a low-end deck. I am really, really surprised!
I hope I can sell this deck to someone who will appreciate it and shows some love for it.

Another update:

The deck has been sold, at a good price I may add, to a customer who is going to use it in a reproduction studio where mainly videotape is being digitized. They needed a good sounding compact deck for an upcoming job digitizing reel to reel tapes. Well, they got a good one. I’m happy the deck is being put to good use and it will be working in a production environment. 😀 🙂

(view count: 2697)