lixaudio
Active Member
Hi everybody,
Few months ago I received a Yamaha M85 in really bad condition - burned right channel and physically damaged (bad package). I've found corroded ground rails on the PCB,because of the fact that some glue change it's chemical stability with age, I presume the lost of ground burned one channel. Found original transistors on the known e-site in UK (yes, they were all originals), replaced some resistors, repaired the chassis and connectors and finally with the help of my much experienced technician fired it on with the variac. Click and apparently with no problems started at the first attempt. Left channel perfect, right channel 22mV of offset (no trimmer for offset). Ok, I can live with that. Set bias on both channels - perfect. Put the dummy load on the right channel - up, up, up, went just below clipping and the relay disconnected the right channel - WTF. On the left channel we've measured the same power, but could clearly see the clipping and no disconnection of the channel. Did I miss something? Probably. Is it possible that just below clipping that offset makes problems (we have measured more than 300W)? Should I leave it so? It works fine and I'm not going to push it to clipping limits.
Thanks,
LIX
Few months ago I received a Yamaha M85 in really bad condition - burned right channel and physically damaged (bad package). I've found corroded ground rails on the PCB,because of the fact that some glue change it's chemical stability with age, I presume the lost of ground burned one channel. Found original transistors on the known e-site in UK (yes, they were all originals), replaced some resistors, repaired the chassis and connectors and finally with the help of my much experienced technician fired it on with the variac. Click and apparently with no problems started at the first attempt. Left channel perfect, right channel 22mV of offset (no trimmer for offset). Ok, I can live with that. Set bias on both channels - perfect. Put the dummy load on the right channel - up, up, up, went just below clipping and the relay disconnected the right channel - WTF. On the left channel we've measured the same power, but could clearly see the clipping and no disconnection of the channel. Did I miss something? Probably. Is it possible that just below clipping that offset makes problems (we have measured more than 300W)? Should I leave it so? It works fine and I'm not going to push it to clipping limits.
Thanks,
LIX