Beogram 4002 (5511) – turns on when it is turned off

[Behsen]

Hello forum.
I’m having an issue with a beogram 4002.  So far I know that the issue is concerning the mainboard – because if I swab the mainboard with another 4002 – the described issue also shows up using the other turntable.

Issue:

When i start playing a record (few minutes play) – and then push on stop – the arm returns and the turntable stops and stays off. The light goes out, the platter stops spinning and- everything looks to be ok.

But if I shortly after it did play  (or if it the first time plays more than a few minutes) – and I push stop  – the arm returns to the base and the turntable turns off only in a few seconds – then it will turn itself on again (the platter starts spinning again – and a week light in the 33rpm display shows up). If I now chose to unplug the power cord and then plug it in again immediately- the platter will start to spin again automatically and the dimmed light will be turned on again.

When the turntable is in this “none stoppable” mode – I can push “start” and the dim light get’s stronger – and the arm moves on and play the record. If I then push stop  – the arm returns to the base – and the light (33rpm display) get’s dimmed again – but the platter will keep spinning now – until I unplug the power cord again.

Do any of you have any ideas of what could be wrong.

BR Behsen

[Mark-sf]

Have you performed a re-cap of the electrolytics on the board? The symptom points to it needing that.

[Behsen]

Actually I had a few (6-7) capacitor’s and I did solder them onto the pcb. Apart from that I’m not sure about how many components I would have to replace. Is it only capacitors – or would it also be transistors etc. And if it would I would need some help in finding the correct ones.

Could there be other reasons for the issue I have described. Broken lamp – /week censor light etc. ??

 

 

 

 

[Mark-sf]

For a start all of the electrolytics should be replaced, Thes are the cylindrical (horizontal or vertical ones) paying attention to their polarity. I would also clean and check the alignment of the switch that is activated by the optical rail when it returns to rest. This should be grounding the base of TR1 via diode D1.

[Behsen]

Thanks Mark.

I have now replaced all of the cylindrical capacitors – and actually also TR1. If the switch you’re mentioning is the on/off switch – I have cleaned it several times.  Nothing has helped so far.

Concerning diode D1 – I think that what you write is according to and earlier version off the turntable (type 5501 or 5502). I have type 5511 – so I might have to look upon D5 instead (but I’m not sure because I don’t have the right version of the service manual).

BR Behsen

[Behsen]

No help possible ??? /  Unfortunately I have not found the reason for the issue yet.

Are none of the experienced members familiar with the issue I have described.

Obvious it is an electrical issue on the PCB board (main board). I’m not sure what to check next. I have measured on all the transistors – and diodes and they looks to be fine. I might decide partly to replace more or less all components on the pcb until the faulty component shows up. I could do so because I have a correct working 4002 also. But I assume that there might be 150 components or more on the pcb – so that is going to be a big task anyway – and I think there also might be a risk that something could go wrong – so I might end up with two turntables with issues instead of one.

However if I begin to exchange components – what would most likely need to be replaced now. (cylindrical caps are replaced – and as mentioned transistors and diodes seams to be ok).

 

BR Behsen

[Mark-sf]

I was referring to the switch marked “SO” that is on the Arm Transport PC board. This keeps the TT off when the arm has returned to rest. Sometimes the optical bar can be misadjusted in its engagement of the switch or it can be dirty as its contacts are exposed. As to D1, I am referring to the diode that is between a 2.2K resistor and the base of TR1. I highly doubt it changed for your type.

[Dillen]

In your case:
A leaky diode, perhaps.
A broken copper trace somewhere, perhaps.
A failing SO switch, perhaps.
Any combination – or something completely different.
It’s impossible to diagnose a problem like this from a distance, and the more you
replace, the bigger the risk of introducing new problems, making it even harder to diagnose.
It’s always easier to locate a fault that was caused from “natural” reasons, like aging etc. than one caused by “something been done”.
Blanket replacing components is a typical cause for strange faults.
Anything can happen – wrong components, wrong polarization, bad solder joints, shorts etc. It can give even experienced repairers a good run for their money.
And it wouldn’t fix f.e. a broken copper trace.

You will have to measure around a bit and diagnose the problem properly.
Or take the Beogram to someone who can do it. These decks are worth any repair.

Martin

[Behsen]

To Mark: You mentioning that d1 is grounding the base of tr1 is the kind of support that I could need right now – but unfortunately the schematics for 4002/type 5511 is completely different than for 5501/5502

Things has changed since the first versions of “4002”. Type 5511 has a resistor (R6/82K) in connection with base of TR1 – and following R6 there is another resistor (R7/18K). So there is no diode D1 in connection with base of TR1. But diode D5 and D8 has connection to the collector of TR1. D5 is furthermore in serial with the resistor you have mentioned 2.2K (R1). I’m not used to look into schematics – so it’s not easy for me to figure out  – but I’m still trying to find out. The switch I have cleaned Is the SO switch and I’m sure It is not faulty.

To Martin. It is not my intention to replace everything in one time – but in small steps – and after each step follow up with testing – that things is working. This turntable will soon be 50 years old. Are there not some of the components that should be replaced now (no matter what).

 

BR Benny

[Author]

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