Den torsdag 30 april 2020 kl. 19:17:52 UTC+2 skrev :
On Tuesday, March 13, 2018 at 9:07:44 AM UTC+1, Bo-Lennart wrote:
Den torsdag 8 mars 2018 kl. 06:35:58 UTC+1 skrev Phil Allison:
Bo-Lennart wrote:

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Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that
-14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc.
If I take out the board labeled B15, the -14Vdc is stable. And I can use
the instrument as a AC-rms voltmeter. No problem. But something happen
the I re-plug the board B15. The B15-board have something to do with
the CCIR-filter (I guess).

But I need a service manual to find out.


** I doubt that it would be much use.

Some component pulling current from the -14V rail to ground on that PCB is drawing way too much. Likely culprits include zener diodes, bead tantalum electros and low voltage ceramic caps.
However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.

If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.



.... Phil

Hi Phil---
Thanks for Your reply.
Some nice guy send me schematics of the power supply board (B16) and board B15.
Was that You???
I checked the Board B15 and found 3 shorted tantal-capacitors, C551, 548, 550.
Changed these capacitors solved the problem.
But there are some more problem with the instrument. In the 3 lowest range 300, 100, 30 micro Volt, the pointer of the movement is not stable. So I will
continue foult-finding. The final problem seems to be in the board B11. This board includes both divider and amplifier. With combinations of these divider and amplifier gives the 15 ranges of +50dB to -90dB.
OK, thanks once again for Your reply. I will continue the foult-finding.
Best regards from SWEDEN
Bo-Lennart Karlsson

Hi Bo and everyone else reading,

I'm looking for the service manual / schematics for the very same device. If anyone has them on hand and could forward them that would be reall helpful.

Thanks!

What is Your e-mail? I only got ".