03-03-2019, 02:48 PM
(This post was last modified: 03-03-2019, 02:51 PM by Old Sparky.)
The preamplifier stages of this model are connected to the Mosfet o/p stages via four plugs, two for each channel. Looking at the diagrams, two 3-pin plugs are employed to connect the pre-amp o/ps to the Mosfet's gates. The center pin of the plug connects to the speaker line, and thence to 0V via the speech coil of the speaker, whilst the two outer pins connect the signals to the gates of the o/p devices via 1k resistors. One plug (PL30 )had been plugged incorrectly so that no signal was being fed to the lower o/p devices, and the center pin was connected to the two resistors feeding the upper pair. Studying the diagram, I can't see how this misconnection could have caused the rectifier to fail, but I'll check the pre-amp circuit for any signs of failure thereon. The circuit can be found on several on-line sources, b.t.w. I'm reluctant to post any part of it on here as it may infringe someone's copyright to do so.
