Hi So/ren

Thanks for the encouragements Yes, I'm almost there but all the same, this has been a difficult job as I have never worked on a turntable quite as complex as this one. Perhaps it is payback time for leaving it unattended for so many years. When it was still working after a fashion about 15 years ago, I used to take it down from storage every year the day after Christmas and set it up to play music for guests who were most impressed by its automated functions.

I could never take it out of the house because of its looks and as a beautiful if complex example of electronic and electro-mechanical piece of engineering.

Regards

dauphine/andre

Hello All

I still need to replace the tracking sensor lamp. Since the existing (dead) lamp was epoxied into the black cover, there is no way to remove the dead lamp without damage to the black cover.

I have salvaged a replacement cover/lampholder from a scrap 4000 but I'm not sure if the lamp value is the same as that of the 4002. I measured the voltage across the place where the lamp goes on the 4002 and this is 21.5V, which seems a bit high for a tiny lamp. Since I am very wary now of burning parts, is this voltage correct, please?

I have also salvaged some identical-looking lamps from the scrap 4000 but reading their specs are almost impossible. Can someone please give some advice as to what type of lamp I should buy?

Cheers

dauphine/andre 

It's a 24V lamp so 21V sounds right.
Current is 25mA I think.

Martin

Hello Martin

Thanks yet again Now I can proceed to the next step.

Regards

andre

Hello All

There has been progress. The new lamp is installed.  I have plenty of the longer bulbs found in the scrap 4000 model but there was only 2 of exactly the same dimensions. One was dead and I blew my chances with the other as it cracked when trying to move it while the epoxy was busy setting.

So I had to use the slightly longer lamp.

Martin was absolutely correct with his diagnosis with the arm which wouldn't move. With the lamp, it certainly does and both arms are exactly parallel.

But, alas I observe the following:

1) I was at long last able tio check the platter speed with the rewound motor and I was able to adjust 33.3rpm to stay as set. 45rpm seem,s a bit fast, but not much.

2) OK. On start, the arm moves to the run in groove, nicely parallel with the sensor arm. I can hear the solenoid click, but the arm does not drop immediately but somewhere midway of the first band. I have already previously cleaned the solenoid's levers and shaft and re-lubricated them. Double check again and all is fine. A few days ago, I noticed the thicker spring of the solenoid was a bit stretched at the top. I have a jar of gazillions of springs and selected and almost identical match.

Symtoms stay the same. Arm drops at the record start, the platter speed is stable at 33.3rpm but the carriage moves the arm far too fast and towards the end of the record, positively races over the last band.

I dont know if this has something to do with the different lamp, ambient light as I was working directly above a room light, or some strange electronic problem.

I am also not sure how important the exact placement of the lamp inside the black cover is. I did not epoxy the lamp as the original was. I used a lampholder from the 4000. This clips directly into the black cover.

Cheers

dauphine/andre

If the carriage moves left WHILE the tonearm lovers (so the needle lands in the music track
rather than the lead-in), you will have to adjust the light sensor/interrupter as per the servicemanual.
In your case the lamp may need a slight rearrangement.
Find the exact point. The carriage is not allowed to move while the tonearm lowers but should do so at the
slightest push to the left of the tonearm.

Have you checked the 33/45 speed trimmers on the main board, they may be faulty. It wouldn't be a first.

Martin

Hello Martin

My ongoing thanks. Yes, it was a bit distressing to watch that needle being dragged across the tracks yesterday. It looks as if I'm getting in here way over my head and technical competencies but I'll do my best. Hope to have better news soon.

I know about capacitor replacements as I have several other vintage items. I wonder if I'm not going about this restore the wrong way. Perhaps I should have started replacing the caps first and then looked at the other issues.

Best regards

andre/dauphine

Hello All

Yes, I'm still around and still trying to fix the 4002. I had to stop work on it for a week or two but started again last night. Small progress - I repaired/replaced the arm sensor cover and fitted a slightly different lamp - same 24V but slightly longer and quite bright which I hope will be OK. I have also troubleshooted the arm up/down function and found two wires detached themselves from the pcb so that's fixed and the function works.

BUT, there are so many other issues left. The other evening, I was looking for something unrelated to the 4002 and found a plastic bag with two used transistors and two new items with almost similar part numbers. And then my memory of work done 10 or more years ago returned.

I remembered that I was looking a long time ago at troubles with this turntable. In my efforts to get it to work correctly, I must have replaced two transistors.

I remember that I visited an electronics supply store and asked for replacement transistors for the two on the pcb's topside and I must have bought two of one type and 1+1 alternative for the other transistor.

I don't know how to test transistors and just replaced two, hoping I could get things to work.

The two pics show the two new transistors soldered into position 10 or more years ago. Next to them, I place the original transistors (probably nothing wrong with them) and the dilemma I have is I am clueless if the replacement transistors will do the same jobs as the originals. Whoever sold them to me, assured me they would work, but sometimes salesmen will tell you anything.

The issues I still have is:

1) Turntable switches on at press of start and platter starts spinning at whatever speed I select.

2) With a record on, the arm does not lower but carries straight on to end of record, returns to rest and the turntable switches off.

3) Manually pressing the up/down now functions but there's no lowering when the platter spins.

I don't know if these issues are related to the two new transistors I soldered in 10+ years ago and I don't know if they will do the same job as the originals (which may very well still be OK).

I also don't know if these errors are due to the fact that I have not yet replaced any of the capacitors. I will remove the board later today and go and buy new capacitors and fit them

If anyone reads this, please help! Would you know if the replacement transistors are OK or should I reinstall the originals?

Regards

dauphine/andre 

The transistors look fine.
Have you checked the functions of the sensor arm (lamp/lens/sensor) ?
Is there a reasonably well defined white spot of light on the record from under the sensor arm ?

If it does not see a record, it won't lower the tonearm, neither automatically nor manually.

Martin

Hi Martin

Thanks again for your kind attention to this ongoing battle I have. Yes, there is a spot of light below the sensor arm which can be seen in my avatar. Whether the intensity of the light spot is OK or not, I wouldn't know as the lamp inside is old. Replacement lamps will probably available from somewhere locally but from obscure places I will have to search for.

I'm still worried about those two transistors I replaced all those years ago. Apologies for mentioning that issue again as I don't really have sufficient electronics knowledge to know exactly what I'm doing.

In the two recent pics uploaded, you can see TIP 120 B7528 was replaced by a new SEC612 TIP 120.

And TIP125 B7537 was replaced by ST99248 TIP 126 (with "Korea" 402 TIP126 as an alternative but never used).

I don't know the functions of these two transistors and still don't know if the replacements will do the same job as the originals.

As I don't think there was anything wrong with the originals, I think I'll put them back.

I will look inside the sensor arms of the two scrap 4000's for lamps to see if they are any brighter than the one in the 4002, or try and find a replacement from somewhere.

Today, I will remove the circuit board again and match up all or most of the capacitors I can buy.

Regards

Andre/dauphine 

Seems your 4002 board looks exactly like my 4004 board that I just fixed. From what I learned about my board, I would say that your two TIP transistors are likely o.k, if your 33 light comes on after pressing "33" and the motors spins (the TIP next to the power entry point turns on the rest of the circuit when the 33 button is pressed), and the arm lowers when you press "down" (or after "start" once the arm is in position-the TIP next to the plug that connects to the solenoid is responsible for sending current into the solenoid). Good luck with your recap. I had two shorted tantal caps in my deck, one of them on the main board (C22).

Rudy

Hi Rudy

Thanks so much for your interest. I wish I could write ".....board that I just fixed."

It is 05:59 here in midwintery and very cold Cape Town.  And this is my third successive all night session this week with the 4002

Yesterday, I bought new capacitors which cost all of only ZAR28.- (about 4 or 5 US$) and took my time to fit them one by one, very carefully - double and triple checked and I'm sure as can be there are no errors.

So I fitted the boards and plugged in. No smoke, platter spins, speed change works, arm lift doesn't so I took the board out again and fiddled some more - mostly again cleaning plugs and sockets.

At least now I have the speed displays to light up for the first time ever, probably in 15 years. And they change over from 33.3 to 45rpm on command.

BUT, in the following hours, more and more issues are appearing which makes me very despondent as I type this.

Suddenly - out of the blue - the 33.3rpm speed seems to have speeded up and 45rpm is struggling well below 33.3rpm.

I tried the motor away from the board with 6V from a power supply and it starts instantly and runs quietly.

As the night progressed I don't know how many times I removed that circuit board but I don't really know what I'm doing.

The last frustrating thing to happen just before I packed up this morning, was that the motor runs with a powersupply but not from the board, wheras it ran perfectly all night after the re-cap.

I really hate writing this sorry story but in a few hours, it will be another day and I'd better get some sleep. Perhaps todaymy problems will be solved. First thing I'm going to do is to put the original two transistors back.

Lastly, some weeks ago when I started with these repairs, I found a small spring (pic) at the top righthand area of the 4002's chassis. I looked for a long time to see where it could fit but see nothing amiss. Would anyone know if this is a 4002 spring or is it something which somehow ended up inside?

Regards all

andre/dauphine 

I really wouldn't recommend replacing components blindly. If any of the components, you put in, are
not fit for the job, if a solder joint comes out bad or a copper trace breaks unnoticed, you will only
have introduced a new fault rather than cured the original and it
will be so much harder to diagnose.

The white Evox capacitors and the Mullard "Tropical fish" types are some of the best capacitors, you
can put in that board. (Check the prices those old fish fetch on Ebay).
They never fail (unless physically damaged) and I see no reason at all for taking them out.
The good news is that the new caps, you put in, looks fine too.

TIP120 is TIP120 no matter the producer.
We can rule out counterfeit semiconductors since you bought them so many years ago.
The B7537 designation merely tells the production date (week 37 of year 1975).

What you need to do is measure the signal from the sensorarm.
Let the platter spin, place the tonearm/sensorarm over the radial ribs of the platter and look
on the scope for a similar pulse signal. Follow that signal through the circuit and watch how it
gets shaped and filtered and eventually validated.
That is the signal the Beogram is looking for to tell if there's a record on the platter or not.
The fault may be as simple as a lamp, badly located with respect to the lens system. 

That severely burned corner of the board where the rectifier diodes are, has that been checked ?

The spring looks like one of those for the dustcover hinges.

Martin

Hi Martin

I just typed a longish reply to the issues you raised and I must have clicked something other than "Post" and whatever I wrote went missing.

Briefly, I understand your sentiment about replacing things unneccessarily and I did so with reluctance as I saw many recommendations to renew capacitors. One of the white EVOX caps was wet outside with a brown, oily substance. All of the tropical fish types had several cracks each and their leads just pulled out - no matter how carefully and gently I removed them.

I have an Iso-tech ISR635 'scope but I am not familiar with the test you recommend. I will try to figure out how to do it.

There are too many remaining issues and I don't want to waste your time by listing them. In short, if one presses START, the arm moves across the platter to its correct stop, returns to rest and switches off. The arm (sometimes) drops like it should, near the last two bands of a record. I have not mis-aligned the ruler but I'll check again.

Today, I must find the correct bulb for the arm sensor (under the black lid) as I think there is too much light coming from the bulb in there now. Also, another new buklb for the sensor wand.

The burned section of the board was repaired carefully and was caused when I plugged the motor into P2. All the diodes were replaced with new items and all tracks repaired and most things worked again after this repair. I will check there again.

Thanks for the clue about the spring.

Maybe today (sunny here for a change) will bring solutions after I've had some sleep which I haven't had for more than 50 hours.

Best regards

andre/dauphine 

OK.
The Evox capacitor is a polyester/metal film capacitor, completely dry.
Any wetness must come from somewhere else.

The ruler provides the electronics with the allowed lowering points and is
read by a lamp (or an IR LED depending on version).
The fact that the Beogram will sometimes start playing at (what sounds to be) the 7inch startpoint
could suggest that the signal from this sensor is what should be checked.
As the tonearms pass over the record, does the speed change from 33 to 45 ?

Martin

Hi Martin

I took a few hours off but I'm starting on the job in a few minutes from now. I traced the oil droplet to a little can of Elna sewing machine oil I used to lubricate some moving parts. All the machines I have here have incandescent lamps in the wand and inside the black cover. This morning, I tried many places for small 24V lamps and until now no luck - all have the B&O types but only 6 and 12V.

For now, I salvaged two lamps from the sensor wands of the scrap 4000 machines. I am replacing the one inside the black cover as it looks far too bright and I will compare the existing working lamp inside the 4002's wand with the salvaged lamp to see if I can get a brighter beam.

The record speed at both 33.3rpm and 45rpm after the capacitor changes was 'believable' at close to that

About an hour afterwards during further troubleshooting last night, the 33.3platter speed increased inexplicably (I'm guessing) to about 50rpm and the 45 speed slowed down to only a few rpm (maybe somewhere between 20 or 25rpm, if that.

If any particular speed is selected, the same speed is maintained over the playing surface. At the end of side, the arm stops, the lifting solenoid clicks and the arm rises and returns to rest and everything switches off.

The first thing I want to do now is to find out why the motor suddenly doesn't work when plugged into the board. then, I want to change the lamp inside the black cover as I think it's too bright and confusing the sensing function.

Next, I want to check and see if any of the salvaged wand lamps is brighter than now fitted, incase THIS may be the cause of the troubles.

I will post as soon as I have more news.

Best regards

andre/dauphine

I was not referring to the lamp inside the sensorarm (next to the tonearm).
I am talking about the lamp (or LED) that shines through the plastic ruler below decks.

Martin

Dillen:

I was not referring to the lamp inside the sensorarm (next to the tonearm).
I am talking about the lamp (or LED) that shines through the plastic ruler below decks.

Martin

Hi Martin

I am very grateful for your continued interest in this repair saga. I still feel a bit silly about changing the original capacitors before seeing your recommendation to leave things alone but this is now 'water under the bridge'.

At one point a week or two ago - after the capacitor change - I had most things working but there were still errors with functions behaving correctly and then not. During test, I often thought about stray light as I had a strong overhead lamp above the 4002 and actually did switch off the lamp to see what would happen. I also learned that the cover plates should be inplace after repairs to really find out what functions do not work properly.

So, the situation is now as follows: The control pad's keys are all working, everything is properly lubricated and cleaned, the solenoid pulls and lowers the arm rapidly with a sharp 'snap', but if start is pressed, the arm travels too fast towards the platter spindle, returns to rest and the platter stops. I fitted replacement lamps in the speed change windows and both 33.3rpm and 45rpm lights up alternatively when the speed change selector keys are pressed.

At this time, I became worried that the voltage measured at P1 was 7.8V and the dc motor is rated at 3V and I don't want a damaged motor again. I am also still unable to check and calibrate the platter speed as repairs are not complete. After the motor was repaired, the rotational behaviour of the platter speed was 'believable' at 33.3 and 45rpm respectively. However, for some reason or other, 33.3rpm now seems to run faster and if 45rpm is selected, this speed is much slower than what it should be.

I had some exchanges of correspondence with beoworld.org member Menachem Y. and we mutually agreed that I pack up the pcb and send it to him for checking over. This was done about a week, 10 days ago so all work on the 4002 is suspended until the board comes back.

Since I am so inexperienced with troubleshooting and repairs to such a complex turntable, I fully realise there's still a long road ahead after the board comes back and I hope the gentlemen here at beoworld.org will continue lending a helping hand and give advice until this difficult job is done.

With my best regards to all members who posted and offered assistance in this thread.

andre/dauphine

Andre,

It's on its way back to you!

All electrolytics, tantalums and potis were replaced as a matter of routine. 

A couple of the big 1W carbon resistors were replaced.

Of course, it still didn't work.

The 2 zeners on the tach circuit were shot.

Once those were done, I had voltage on the motor connectors and IC3 C1003 (never did find any info on that elusive part).

Then I was willing to connect the motor for the first time, and I got a beautiful square wave off pin 6 - the Schmitt trigger.

I calibrated the 5 potis, ran it for an hour, playing my LP's (and thoroughly enjoying it). 

No abnormal temperatures or smells, so I packed it up and mailed it.

Should be a week or so, and let us know!

Best of luck!

Menahem

Oh yes, and here's a pic for all the interested parties on how to connect the plug-in cables without guesswork

Hi Menahem

What can I say Thank you very much for taking me out of audio's equivalent of a "black hole". The road is not at its end yet and I faithfully promise to only work on the 4002 when I've had a full night's sleep

Menahem even sent me a little video to show the rejuvenated board works on another 4002 - much appreciated.

I look forward to posting here again when everything is back together. This will be a real 'blast from the past' as I have last listened to it more than 20 years ago.

dauphine/andre

Hey Guys

I write to thank you all - YachadM (Menahem) Dillen (Martin), Harry Pierce, So/!!ren and my apologies for leaving anyone out which I think I have.

I have been playing records all day long while I made some minor adjustments (not to the board, Menahem) and did a motor swop about an houyr ago which corrected the speed issue on 33.3rpm. As you can see, the covers are still not fitted properly as I still have some more work to do inside. I want to have a look at the pitch adjustment pots (hope there are any inside) as both 33.3 and 45rpm speed adjustments are non-functional.

The remaining issues are that the motor slows down well below 33.3rpm if 45rpm is selected. Also, if a 45rpm disc is on the platter, the arm moves just inside the platter rim and no further.

The third of the 3 remaining issues is that the arm's up/down function doesn't work although the control panel's corresponding key is functional.

At 33.3rpm, the arm moves smoothly to the lead-in groove, the platter starts spinning, the arm drops accurately and plays through all bands without distortion. At the leadout groove, the arm lifts and returns to restwhile the platter stops rotating - something it last did very briefly 22 years ago.

It may be a bit premature but I think my dark, cold nights are almost over.

Thanks once more to all here at beoworld.org for all your help and advice.

dauphine

Hi All

I write bringing good news that I have been listening to records all day on the 4002 Initially, the 33.3rpm speed was very much too slow but this improved to about 5% off by yesterday morning. After a motor swap a few hours ago, things are spot on.

So, it is time to thank each one of you who read the gory details of the many dark, cold nights I sat pondering the 4002's problems and tried this and that. My special thanks to Dillen (Martin) and YachadM (Menahem) as this was an absolutely international collaboration to assist this old bloke so magnificently and with so much patience and good humour.

There are still a few things to get fixed. 45rpm spped is much slower than 33.3rpm and the arm doesn't move to the 7-single position, even though the control keys are all functional once more. And the up/down function is also still not working but I'll get there

The pics show nothing is yet properly covered-up as it is still "work in progress".

I think I should also mention that the main pcb flew to MenahemY in Israel who kindly undid all my butchery and then did a marvelous job in a most impressive short time.

Once more, I thank you all. as soon as all things come together, I will show a pic of the end result.

Regards

dauphine/andre

Sorry about the double post.  There was a problem last night with the forum slow to load.

Btw, has anyone attempted to improve or brighten-up the anodised surfaces of the top plates? Obviously, the brushed effect has to remain. I have some spare covers here and was thinking of making a test. I have anodised aluminium and know most of the processes, pre-preparation and have the chemicals and equipment to anodise aluminium.

One of the pre-preparation methods is to degrease and 'chemically' polish in boiling phosphoric acid before anodising. My baths are too small for the 4002's plates but I'm thinking of boiling some phosphoric and using rubber gloves and protective clothing - just wipe the plates down rapidly and rinse almost immediately with water. To strip anodised aluminium to base, boiling in phosphoric for no longer than 1 minute will be sufficient to get old anodising off. I don't want to do this ofcourse - just a few seconds of phosphoric contact should result in a freshly anodised surface as I have seen many times.

Or is there a better way? Anodised surfaces are very hard and most polishes will likely have no effect. 

Regards all

andre/dauphine

I'm waiting to hear the good news!

For that 45rpm problem, just a wild guess - check that the solder blobs on the thin PCB holding the 2 24V lamps are all correct with no blobs touching adjacent ones.

If you find a workable solution for the aluminium, we'd definitely like to know about it.

Menahem