I am confused. In the photo you show capacitor C28. That is a 47uF, 10V electrolytic capacitor.  C24 and C27 are on the main board.

Anyway, I always change out C28 on a Beogram 8000/8002 restoration. It is key in the +5 VDC power for the microcomputer IC.
I change it when I am changing out the IC socket as it is much easier to get to when the microcomputer IC is out of the way.

If you just change C28 where it is you could just snip the existing leads and solder on to them. I don't like doing that unless I absolutely have to.
It is tight getting a soldering iron tip in there. 

The way the red and blue wires for the tiny board inside the microcomputer box are connected vary.
Here is a Beogram 8000 I restored that had them connected to +5 VDC and ground differently.

 

I’ve not changed c28 yet. Just the middle big cap on the main pcb (which is I believe c24?)

I’ve just had a go at changing c28 in the cpu can (it measured about 36uf) and I’ve managed to damage the negative pad on the top side 🙁

I agree - it's not exploded. But it's one I ALWAYS replace so I suggest doing that, though it won't most likely not be the reason for the current problem.

Martin

I’ve managed to change the cap in the cpu can but as expected it hasn’t changed anything.

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Is the shielding on this cable supposed to connect to anything?

That wire is attached to the correct place.
Originally it was not soldered to the post on the board like yours is. The wire was attached to a single sleeve that fit onto the post.
Either way it is connected and the wire goes to the Microcomputer box.

I re-read this thread and have to ask if you checked the fuse that is inside the transformer box?

After that I would tackle the Beogram 8000 power supplies.
Check the DC voltages on C24, C27 and C29.  Then the +5 VDC capacitor C28 at the Microcomputer assembly.

-sonavor

The fuse in the transformer box tests fine.

These are the voltages I’m getting.

C24 - 9.29v

C27 - 19.94v

C29 - 21.62v

Cap in cpu box 1.05v

Hi Lee,

Those are a little low I think.
I usually get around 12 VDC for C24, 24 VDC for C27 and -24 VDC for C29.  C28 should have +5 VDC of course.

You are measuring about 3 volts lower on everything.
however, those should be enough for the regulators to produce +5 VDC, +15 VDC and -15 VDC so I don't think that is the problem.

I suggest pulling and testing 0TR1 as it sits between C27 and C28 to regulate the +5 VDC supply line.

-sonavor