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 instrum ent as a AC-rms voltmeter. No problem. But something happen the I re-plug t he board B15. The B15-board have something to do with the CCIR-filter (I gu ess). But I need a service manual to find out. Maybe someone out there, kno w exactly what's wrong here.
Best regards from SWEDEN Bo-Lennart Karlsson Falun, SWEDEN