Second picture is measuring across the same fuse holder with the unit switched on........

The standby current looked high to me....so I measured from the same place in one of my fully functional decks....this is what i got  

Same deck, same measuring point with the unit switched on......I will get to the secondary windings later in the day hopefully

Hi Craig, thanks! Yes, 71mA (or 18W) is definitely too high for standby. The 25mA or 6W look reasonable for a product from the seventies.

But without seeing the idle current on the primary winding when all loads on the secondary windings are disconnected we still do not know the source of the problem. Granted, the fact that the turntable seems to function normally suggests that the neon lamp winding is the culprit...but well, it's still just an assumption and not a known fact.
To make it a fact you need to disconnect all secondary windings from the circuits and measure again. If you still read a high idle current, you know that the faulty neon lamp winding is to blame.

Well......got around to it this afternoon, disconnected the remaining two secondary windings and powered up the unit 56mA.............I think we have our culprit, the question is can anything be done about it? 

Craig wrote:

Well......got around to it this afternoon, disconnected the remaining two secondary windings and powered up the unit 56mA.............I think we have our culprit, the question is can anything be done about it?

Yes, that leaves no doubt, I'm afraid.

Let's crunch some numbers:
71mA - 56mA = 15mA -> That's the supply for the idle current on the 24V and 10V coils.
The good unit draws 25mA in standby, ergo 25 - 15 = 10mA -> That's the magnetizing current in the primary coils.
56 - 10 = 46mA -> that's what's dissipated in the rogue neon lamp coil (which acts as a heater now 🙁 with 46mA * 240V = 11.04W).
Previously you measured 165V instead of 220 on the neon coil and 900 Ohm instead of 1.3k, i.e. we do have a short within that winding and that thing burns 11W. Based on P=I^2*R and the 400 Ohm missing, we get I = sqrt(11/400) = 166mA and they are circling in that shorted sub-coil.

Hmmm, now that doesn't sound so good. Depending on wire gauge, this might be a real problem. If that trafo wire is SWG30 or bigger (=0.315mm diameter or smaller) this could cause more insulation meltdown potentially even affecting the 24V or 10V coils.

The best and safest option, of course, would be to replace the transformer...but if I remember correctly, you tried that before and it proved difficult...

Hmmm...if I were in your shoes, I'd probably test the transformer for a full day (outside the Beogram and in clear view, of course). I'd measure the trafo temperature with an IR thermometer, hourly or so, to see the max temperature it reaches and then I'd decide whether I could live with that. You said it gets "hot" and I assume that is around 60+ degrees Celsius. Even though that is uncomfortably warm it wouldn't be much of a technical or safety problem. If it gets anywhere near 80-90C, then forget it. It's definitely unsafe.

I would opt for spending the money to have a new, toroid transformer built to spec for the Beogram 4000.
The only downside there in my opinion is the cost.
Just my 2 cents but seeing how this is a classic, much sought after turntable (by B&O collectors), it would definitely be worth the cost to get it back into full operation again. 

With the restoration work Craig has already done so far this Beogram 4000 would be ready for another fifty years of enjoyment.

-sonavor

Thanks for the support chaps.....

I don't have a IR thermometer, but I know that if something is too hot to touch its generally accepted as above  60 degC. In my view leaving this unfinished isn't an option....however the final say has to be with Justin. He will have to justify further outlay for a replacement transformer, providing one can be sourced of course.............anyone out there got a transformer they don't have a need for  

sonavor wrote:

I would opt for spending the money to have a new, toroid transformer built to spec for the Beogram 4000.
The only downside there in my opinion is the cost.
Just my 2 cents but seeing how this is a classic, much sought after turntable (by B&O collectors), it would definitely be worth the cost to get it back into full operation again. 

With the restoration work Craig has already done so far this Beogram 4000 would be ready for another fifty years of enjoyment.

-sonavor

sonavor

Had a quick chat with Justin this morning and we are in agreement that a replacement transformer is the way forward, we have searched in vain for  a replacement and now think a custom built toroidal transformer may be our best bet...as you have already been down this road could you provide contact details and a specification for the unit you had built for your unit?, of course we would be looking for a 240vac primary winding version....

Regards Craig

Craig wrote:

[...]  In my view leaving this unfinished isn't an option....

🙂 🤒 Good decision!
And even if a custom-made transformer is beyond reach, all may not be lost just yet!

I did look at the design of the power supply yesterday, trying to figure out why it is made the way it is...and I think from a perspective of modern electronics there is room for improvement/simplification.
I see no technical need for a split 10V, 24V power supply. I guess the B&O designers did this to avoid interference between the logic board #3 and power-hungry parts in the analog circuit (motors, solenoids, the Byzantine reed relays, etc). That's not really needed. You could safely run the BG4000 on an off-the-shelf 2x12V secondary by replacing 2TR6 with a modern 6V LDO regulator. That costs you $2 and 5min of time. The transformer you could get from digikey for EUR20.- to 40.- max (and those are even 115V/230V dual windings on the primary!).

What it boils down to, however, is the real estate you have available for the trafo. What is the size of the current transformer? From pictures I'm estimating that you have at least 70x70x40mm of space available....that's tight. 80x80 or even 85mm would be better and would allow the use of many standard toroids.