M-60 problem

OTL Asylum

OTL, Output Transformerless Amplifier User Group.

0

I am having a problem with my M-60s. I tried Kurt Strain's mods and they didn't provide enough gain. Fine. Put the cascode and cathode follower back. Now they are stock again except for 2 things. The output supply capacitance has been increased to 8800 uf and the feedback resistors have been removed.
I am having DC offset problems. I can balance it at the grid resistors for V3, but grid voltage on V5-8 is ~-75v, while on V8-12 is ~ 4V. This is in standby. When powered up, V6 goes into thermal runaway. And I blow F3 like crazy.
I bought the units used. They were factory built and didn't come with a schematic. Can someone help with some diagnostics and test points so I can figure this out? TIA

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The Cable Cooker

Topic - M-60 problem - Old, gray and definitely in the way 15:54:14 05/24/99 (1)

Re: M-60 problem - Ralph Karsten 19:23:29 05/27/99 (0)