Pars Posted January 28, 2011 Report Posted January 28, 2011 Check the PCB over carefully in that area as well. They can sometimes be under-etched with a bridge or the like...
fishski13 Posted January 29, 2011 Report Posted January 29, 2011 Yay, 1 channel running. Noticed some very funky instructions in the Pass guide to this amp - it says to start with both trimpots at minimum - that resulted in about 8V across R12, had to very quickly adjust it to get a more reasonable voltage, was scared I burned something. Second channel is getting some funky bias settings (where I reversed PSU polarity), replaced R11/R12 and 450/550s and the input jfets, but can't get above 0.4V across R11/R12. Could the mosfets be fried? It sounds strange, as I'd expect to get 0 output then. This board was getting 0V across the resistors before I replaced 450/550s. No change after replacing the jfets. Any ideas? I'm a little lost, not really sure what to replace next, except the mosfets as all the resistors look fine (not burned). i used the Vishay-Sfernice T93YA trimpots and "minimum" = fully clock-wise. also, i got very little V movement with rotation and then, bam, i was sitting at 1.5V.
FallenAngel Posted January 30, 2011 Report Posted January 30, 2011 Hmm... I started with the trimpots fully counter-clockwise, no wonder it starts at such high voltage before. I'm thinking that explains a bit. Wandering which part is burned again, but good lesson learned.
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