On Thu, 17 Dec 2015 05:22:59 -0800 (PST), "
wrote:

Amen to that- the working unit to compare!

I finished the Dynaco ST120 from hell last night. It came to me "fuzzy in one channel". And it was.

First run-through: One output transistor in the 'good' channel, one output and one driver in the other, still fuzzy. I wound up ohming out every part, comparing to the good channel. Six drifted resistors later, I got to the 5.1V zener diode. Bingo. It had become a 94 ohm resistor.

Given that these beasts blow up by the numbers, I generally install sockets for the outputs, and do the TIP mod once ALL else is under control.

Peter Wieck
Melrose Park, PA
Peter,

Who in their right mind would still be using one of these? They were
considered to be an awful amps back in the 70s. One I saw burned down
a house. The carbon resistors caught fire and there happened to be a
curtain draped across the top of the amplifier. After seeing this
amp, I refused to work on them.

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