Vintage Products

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 04 Nov 2011 22:21:26 GMT

Hello Guys

Yes, I'm still around[:)

I have been working intermittently on the 4002 (and also been listening) quite a lot but that 45rpm speed issue has been with me for many weeks.

So, on Monday this week, a tech friend came to visit and we spent quite a few hours with my 'scope hooked up and eventually homed-in on the possible cause of the slow-running 45rpm speed.

The problem was the fine speed adjust 1kOhm linear potentiometer. For most of the time, the 45rpm speed was selectable (but running much slower than 33.3rpm) and a few days ago, I cleaned it in situ once more with a fine brush, a bit of compressed air and some contact cleaner.

Despite the careful work, the motor stopped running and on Monday this week - after my friend had left, I desoldered the part and dis-assembled it completely.

I immediately saw that the carbon track inside had disintegrated near each connecting pin and decided to try some Leitsilber L100 conducting silver paint to 're-connect' the pins to the carbon track.

I applied 3 coats with a fine brush around the corroded areas and let the paint dry before re-assembly. And it worked!

I now have 45rpm speed again.

I hope this experience helps the 4002 owners here.

As I had taken the 4002 completely apart again, I started re-assembly this evening. Installing the cover plates is quite a job and required a bit of gentle tapping with a piece of hardwood to get the plates to fit.

After this job was done, I tried a record on the platter and...the arm would not drop

A million thoughts about possible causes later, I thought I'd visit here and look once more at pics I posted in this thread.

I think I found the cause of the problem. One of my pics clearly show there are TWO springs fitted near the arm mechanism, solenoid and damping cylinder.

The lefthand spring must have dislodged itself during re-fitting of the cover plates.

I have spare springs but I will HAVE to find the missing spring as it could be somewhere inside and could cause a short or interfere with the carriage transport.

Never a dull moment...

A fine weekend to you all.

andre/dauphine

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Sat, 16 Jul 2011 20:04:59 GMT

Hi Menahem

It's good to read your message

I still have that speed problem. At max + on 33.3rpm, it still runs about 3 to 5% slow. Although the belt is in reasonable condition, I will pick up another on Monday. I have not yet glued the motor pulley but I don't think there's any slippage. The 45rpm still runs considerably slower than 33.3rpm and when a 7- single is placed on the platter, the arm moves up to the platter's rim and that's it.

So this afternoon I started another session of work. First, I dismantled the speed indicator display and found the 1kOhm? linear pots almost inaccessible so I did second best - used some contact cleaner and worked them from side to side and now it has some speed adjustment capability.

I reassembled everything and started work on the keypad. I removed the stainless surface plate and removed the board and found the up/down control jammed to continuity and fixed that. Then I found there were two of the multipin connector's wires hanging by 1 thread and fixed that.

While the stainless key surface was off, I decided to remove the finger wear marks.

I did this using a 3M sanding pad and discovered the surface was varnished. The finger wear marks were into the varnish. No problem, I mixed some automotive satin clearcoat and hardener and gave the plate a few light coats with an airbrush over the freshly sanded surface, restoring the surface as new.

So I re-assembled the control panel and all the current problems are still there

I am not sure if any of the components on board 8(?) under the control pad could have a bearing on the the problem. I see there's a pot and capacitor there, as well as a relay.

I will check the thin pcb for touching solderpoints - I am alert to such errors but will doublecheck.

I think one can reasonably rule out the motor for speed difficulties. It runs silently and freely with no screws overtightened. And it is lubricated - as is the platter bearing. As I now have two dc motors (including the one with the rewound rotor) both (mis)behave similarly).

Question: Will it be possible to simulate the 2 motor speeds with a bench power supply with digital display? When I repaired the original motor, I tested it with 3Vdc + at the red wire and - at the centre blue, drawing 0.12A. If for example the same voltage is applied to + to the motor's white wire and - to the blue, the motor also runs clockwise but slower, drawing only 0.04A. I am writing now about the rewound motor. The motor in the turntable now is a motor which was given to me by a very kind US 4002 user. This motor was sent to me in pieces and as 'not working'. I re-assembled it and tidied up some bad soldering to its pcb and got it to work. Later this morning, I will double-check to see if the two motors behave similarly.

The main pcb can also be ruled out as it was proved to be working correctly. All testing done the last few days is with the covers still not fitted properly, nor is the cover on the arm mechanism. There shouldn't be a problem with light confusing the issues as all covers are pushed close together to exclude light.

If the 33.3rpm arm function is correct in all respects, can one assume that the 45rpm arm operation will also be OK? I'm thinking specifically about the ruler's position (I marked its position) and or the positioning of the newly fitted LED?

My 4002's cover plates are in relatively good condition. Years ago, I fitted a mono switch (just bridging L+ and R+) but may revert to another plate from one of the 4000's which may have to be modified a little to fit. These plates are a little dull and I may try the phosphoric trick on them. For the uninitiated, this could be dangerous but if I do it, I will post some safe directions for the not so fainthearted.

Regards all

dauphine/andre

Re: Beogram 4002 Series 5511 Restoration/Repairs

yachadm — Sat, 16 Jul 2011 13:17:04 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Sat, 16 Jul 2011 04:40:16 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 15 Jul 2011 17:52:00 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 15 Jul 2011 17:14:44 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Tue, 28 Jun 2011 17:09:51 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

yachadm — Tue, 28 Jun 2011 04:43:39 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

yachadm — Tue, 28 Jun 2011 04:41:48 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 17 Jun 2011 05:22:34 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Dillen — Fri, 17 Jun 2011 00:22:14 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 03 Jun 2011 12:43:55 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Dillen — Fri, 03 Jun 2011 07:16:07 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Andre — Fri, 03 Jun 2011 03:32:34 GMT

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

Re: Beogram 4002 Series 5511 Restoration/Repairs

Dillen — Fri, 03 Jun 2011 01:58:02 GMT

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