Suggested start up should have the PS disconnected from the amp boards.
Also use a variac or dim bulb tester or both.
Variac
http://en.wikipedia.org/wiki/Autotransformer
dim bulb testers
http://www.diyaudio.com/forums/power...lb-tester.html
Bias Setting(thanks to ZM)
dial both pots to 0 ohms ( check with ohmmeter )
place one voltmeter across PSU caps ( best between + and - of PSU) to observe max voltage of PSU
place one voltmeter at output - to observe offset
place one voltmeter across one source
resistors(R11 or R12) of output mosfets ; it doesn't matter which one .
for test - slowly dial up Variac ( presuming that you have one , as man with many skills) up to full mains voltage , observing voltage at PSU ....... thinking about max cap voltage ( 25V as in FW ? ) , because with 0 Iq PSU is unloaded and voltage is maxed
if nothing is smelling :rofl: - leave Variac at full mains ;
what's important - Iq must be very low , offset is irrelevant in this moment .
now turn one pot one turn ( assuming that you have multiturns )
then turn other pot one turn
observe Iq and offset
proceed one then second pot , again just one turn
observe Iq and offset
again one turn + one turn
now you are probably in range when you can see which pot is pulling offset in right direction - to 0 .
proceed iteratively with pots , while you set - say - 75% of desired Iq and
zero offset
now - put lid on box and let it cook for a while - until yo get thermal equilibrium on heatsinks
it's best to use wire/clips to leave those voltmeters in place ;
open the lid , up bias to - say - 90% of desired one ,while maintaining offset
put lid on , let it cook
check ;
if all is OK - move voltmeters for Iq and offset to other channel and repeat procedure
use it few days at 90% of desired bias , then check and set to 100%
remember - temp. equilibrium with lid on is important
simple , isn't it ?
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