Setting bias on Sansui AU4400

[hew128]

Hi,

I have a Sansui AU4400 which was just repaired by the shop. He fixed my 'crackling' sound on the left channel but did not have the service manual to reset the bias afterwards.

Can anyone help with the details? Thanks!

[nigelwright7557]

With my designs I start off with zero bias and slowly wind it up until crossver distortion goes. You need to have a speaker connected to do this. Yo ualso need a sigan generator and a scope.

There seems to be an obsession with some designers to make extra current go through the output pairs but this is just wasted as heat.

So long as there is no crossover distortion in normal use the setting is fine.

[hew128]

Discovered one channel was set to about 49mV and the other about 15mv. I have since set both channels to about 15mV and seem to be working fine.

Replaced all electrolytics except for the large 2200uF 50V. So far excellent results and sounds like a tube amp!!!

[Maros]

Well, just for other folks with cracking speakers with the Sansui AU-4400 : check your fuses, and their connections to the board.
Check continuity whit yer' meter on the beep-mode, and if it doesn't beep, the fuse or connection is bad.
Replace the fuse or bow the fuse holder a slight bit inner wards.
Well, this learned my Sansui not to grumble

[amptech]

Originally Posted by hew128

Discovered one channel was set to about 49mV and the other about 15mv. I have since set both channels to about 15mV and seem to be working fine.

Replaced all electrolytics except for the large 2200uF 50V. So far excellent results and sounds like a tube amp!!!

Rule of thumb would have been to use the working side to set up the bias.. that's been done..and all is well