[Ron Ramirez]

After the successes of the 700-T and 440-T, I decided to revisit this one. After all, it's only been eight months, almost to the day.

I went over every solder joint on the amplifier board, reflowing the solder.

Here's where I am at on this one now:

The right channel now sounds OK through the speaker. The left channel has heavy distortion. I saw it on the scope, all the way back to Q7. I pulled Q7 and tested it - it is OK.

Then I remembered there is feedback from the output to Q7, so I suspect this distortion is being produced at the output transistors?

I remeasured voltages with the unit set to the AUX position, no input. Yes, the voltages are very stable that way. The voltages, comparing the transistors on the left channel to the transistors on the working right channel, pretty much correspond to one another. The only difference was found at one of the output transistors; the base of Q17 (left channel) reads 0.5 volts while the base of Q18 (right) reads 1.3 volts. The schematic calls for 1 volt. Both Q17 and Q18 measure 0 volts at the emitter - the schematic calls for 0.4 volts.

I re-uploaded the schematic to the server of this website, to make things easier:
http://www.philcoradio.com/images/Fisher_170_schem.jpg (964.9K)

Thoughts?