so just how good are you guys?

[lumanauw]

another RCA

 

[wg_ski]

i mean, i believe the likeliest failure scenario was the left channel OPS blew, shorting the collectors to the emitters of the OPS transistors. this in turn caused a massive overcurrent condition in the PSU because at this point the top and bottom rails were essentially tied together due to the shorted OPS transistors. this overload caused the rectifier diodes in the PSU to overload and fail as well, shorting out the secondary winding of the main trafo. this, of course, could have easily led to a fire.

The rectifier diodes are the key. When they fail due to overcurrent, they almost always open up. By then the trafo will be pretty hot, but probably not enough to start a fire.

 

[gain]

lumanauw, many thanks for the schematic. even though none of these are close to the animal i have, they are very interesting designs to look at nonetheless. mine has 4x2SC830 on the outputs, no output coil and four diodes tied together in a tree for bias spreading. again, thank you for the diagrams, much appreciated!

does anyone remember how these sounded? the ones lumanauw posted.

 

[gain]

The rectifier diodes are the key. When they fail due to overcurrent, they almost always open up. By then the trafo will be pretty hot, but probably not enough to start a fire.

i know, but these shorted. perhaps i am overlooking something in my failure scenario, i wasn't there wen it happened, scored it at a yard sale so i have no idea what really happened. alls i can say is that when i went to fix it all OPS transistors on left channel were shorted collector to emitter. base to emitter junction said OK on diode check. all the emitter resistors on the left channel were cooked. this is what made me assume the overcurrent condition led to the failure of the PSU.