My Beogram 4002 suddenly stopped recognizing 45 rpm records. The tone arm passed the LP position, changed speed to 45 rpm but then missed the 45 rpm record entirely and returned to the rest position.

Following this my 4002 would not acknowledge an LP record, manually stopping but REFUSING to drop the arm on the unforeseen record. Multiple efforts achieved the drop of the arm... but it wasn't easy!

The next day it was like none of the above had happened, with the 4002 performing like it ws new.

What is going on here?

Jeff

Sensor arm lamp output is becoming marginal (filament degrades) and/or positioning with respect to the lens is "on the edge".

Martin

Thanks Martin,

Either maybe the case. It also maybe the lens is dirty after all these years. Maybe....

In any case, the 4002 is again playing records, at least for now.

Jeff

My 4002 which was working perfectly will no longer 'see' a record it just goes to the end (changing speed 1/2 way) then returns. I can clearly see the light on the sensor arm shining on the record and the B&O logo is illuminated (same bulb?)  Putting a piece of black paper under the sensor arm whilst it is trying to play will not trick it into working. As it was OK, I take it the adjustments are OK, at least nothing has moved.

No caps have been replaced in this set (yet)  Where would be the best place to start looking?? Thanks

The best thing would be to put an oscilloscope to the sensor signal path. Alternatively a DC voltmeter where shining a flashlight on the sensor (I use a dentists mirror for this) should produce a DC voltage from the sensor. The sensor is a tiny piece of glass, it breaks quite easily (I have new ones in stock if you need, not the easiest part to replace though).

Check for the usual issues; Cracked solders, bad connectors etc.

There are some tantal capacitors on the circuit board and I've noticed them starting to fail, however pointing a finger to one particular component is impossible without measuring about a bit first. Check the sensors output first.

Martin

Problem was a bad connection to the solenoid. Re-soldering seems to have cured the problem

Well the problem has returned.There seem to be 4 wires coming out of the detector arm. The manual is not clear which provide the signal. could you advise which colour wires to test between and what sort of voltage to expect. Thanks

just to bump this up, does anyone know which wires to test for an output from the detector arm?

Thanks

OK the sensor is producing an output back to the board under the deck.

I notice the manual raise/lower switch will not lower the arm either. Where do I look next?

Thanks

OK - I have now dismantled the deck and diode D 17 is physically broken. It was bent over the power transistor (presumably from manufacture) and moving the deck must have caused an impact!

It is a BZX79 15V Zener 5%. The nearest I can find is 16 V which is too much.

Can anyone help. Happy to pay- send a PM

Not sure if this is the problem but it can only help.

D17? Are you sure? It's just a regular 1N4148 in my schematics.

The only 15 volt zener I can find is 1D10, and it's job is to regulate the voltage to the detector lamp. Can't be that critical (although I would replace it with something lower if you can't find the exact value, like 13.8V).

Anyway, a failed D17 makes a lot more sense for the problem at hand.

Hi Its the one pointed to by the biro. The symbol on the underside is for a Zener

Don't blindly trust the markings on the PCBs, they are sometimes incorrect.

But, unfortunately the PCB in your picture doesn't match either version in my 4002/6000 service manual. You probably have an older/newer version that isn't covered there, so I better let someone else take over with the specifics. There are anyway some diodes in the solenoid driver / control circuit that would prevent the arm from lowering if they are broken.

There are many different versions of 4002's.
This particular one looks like a type 5511, 5521 (or maybe 5525) and
there seems to be some confusion in the service manual.
D17 is shown as a zener but listed as a 1N4148 (which is a standard diode).

Judging from the colors of the diodes on your board, D17 definitely looks different than most
other diodes, so my bet is that it's a zener, it would make sense circuitwise as well but we
need the value.

Maybe someone has a similar Beogram to check the exact lettering on D17 ?
Sadly, I don't have access to any at present.

Martin

Thanks everyone.

On the power transformer it says GR4002 type 5514. Attached is a picture of the underside. You can see the hole where the chassis screw went and broke the diode! Again the biro points to the position of the diode. Hopefully someone else with a 4002 in bits will have one of these D17's intact as there is not enough to see. What I can see with an eyglass is flesh coloured paint which is similar to the other ZPD diodes

I have the correct service manual and the diode ID17 is listed as 8300053 (B&O part number - not useful!) ZPD 15V 5% BZX 79 15V

It is in the automatic lowering circuit.  In the earlier model, ID17 is not individually given a type - listed as IN4148  SFD184

I do have the circuit diagram if needed.

Think I have found some for sale here.

Hi PWH

I wish I could help you here, but as Martin already pointed out, there is a discrepancy in the Service Manual.

Can you remove the diode, and try (with a magnifying glass), to see if there are any numbers or letters readable on the diode.

Before you remove it, make sure that you mark the polarity of the diode on the PCB - the cathode is a black ring around the glass tube, and I usually mark the cathode end with a black Permanent Marker on the PCB.

One thing for sure, is that all the other Purple (cathode-side) and Orange diodes on your PCB are 1N4148's. So, if it resembles one of those, it is probably a 1N4148. BUT, if it has a clearly identifiable Black ring, then it's probably a Zener.

Pls note - the color coding I mentioned above is NOT applicable universally today, and today almost all glass-diodes today look the same (Orange with a Black ring), irrespective of type. They will have some imprint of tiny numbers on them to denote the diode type.

Let us know what you can deduce - I have plenty of either of the possible diode types in stock.

Menahem

One bit of diagram - afraid no picture of circuit board - they are no longer provided - just the grid.

And one of the listing.

Hi Menahem,

I have plenty of 4148's but not the other type. Assuming they are cheap to post can I buy 2 from you? please send a PM with a price.

Thanks

PM sent!

And BTW, I just found this off a Tech database:

Plays only 30cm records – Arm does not stop for 17cm

Replace capacitors C12 (2.2µF) and C16 (0.1µF) in detection arm unit.

Check to see if this is applicable to your type - check the ESR's of the caps.

Just scanned and uploaded the manual for the Beogram 4002 and 6000. This one covers the following models:

T5514, 5515, 5524 + 5527.

Full circuit diagrams and some additional service tips at end. Due to our manuals being downloaded and then sold on eBay, this is, as with all our new manuals, stamped and copy protected. I realise there are ways around this but it will take a bit more effort!

I have now received the diode from Yachadem, Thanks.

To be certain, before I replace, The black stripe is the cathode? and goes to the collector of the transistor? in the circuit snippet above.

Yes, the black stripe is the cathode.

Yes, assuming that the diagram is correct (and I would double check it against the existing diode on the PCB), the cathode goes to the collector.

Menahem