- Need a service manual SENNHEISER UPM 550-1 - 2 Updates
| Bo-Lennart <bo-lennart.karlsson@telia.com>: Mar 07 09:24AM -0800 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. Maybe someone out there, know exactly what's wrong here. Best regards from SWEDEN Bo-Lennart Karlsson Falun, SWEDEN |
| Phil Allison <pallison49@gmail.com>: Mar 07 09:35PM -0800 Bo-Lennart wrote: ------------------ > 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 |
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