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Phase Linear 400 repairs?

Regarding output transistors, I've upgraded two 700's with better, faster ones and neither amp oscillates, and I think if they did the situation is usually rectifiable.
 
Is the hum 60HZ? Most PL amps aren't hard to diagnose, but there are those exceptions where a resistor is out of spec, a trace is separated but is almost invisible.
There's an awful lot of info out there on tranny substitution, the main gist that you don't mix output types in the same channel. I finished my second 700 SER 1 using MJ15024's as drivers and MJ21196's as outputs, no problems. also used 15011"s driving 024's XPL909's eytc.
The only way you'll know if it will oscillate is to put it together and put the scope on it.

qboneus, PM me if you need some parts.
 
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