Update from Ashdown on 60H bias-FYI

[Mars Amp Repair]

Also see schemo attached

From: Guy Morel
Sent: 25 May 2007 10:47
To: glen@marsamprepair.com
Cc: Martin Burrows
Subject: RE: Ashdown 60


Hi Glen,

The Peacemaker 60 is actually an Auto Biassed amp. The biasing is
developped by R47 and R61 in the cathode Circuit of the EL34's.
Initially, they were two 390R resistors in parallel on the board.
These were uprated and moved off the board and bolted to the chassis ( 2
x 100R in Series ).
The actual Grid bias on the valves should be around -30volts. The
-12volt tap was to ensure the valves did not overcook themselves while
the Auto biasing was establishing itself.

Regards,
Guy

[Mars Amp Repair]

also it turns out this is a Class A amp, hence the higher bias setting for the EL34's.....approx 60ma ea. glen