Perform Biasing on B&K ST-140

[Falcon]

Hi Forum Members:
I have just replaced the pre-drivers and output drivers on both channels of my B&K ST-140 ( early version with only one pair of output transistors per channel ). I would like to know what is the procedure(s) to check and setup the bias on both channels correctly. Also anything else I need to check and adjust to make sure that everything is fine and within specification? I contact B&K but no response so far. Thanks.


Mike

 

[djk]

Pull one fuse on one channel, adjust the bias to about 125mA (100mA per output plus 25mA for the front end). Repeat for the other channel.

 

[jonnymyaudio]

Bias

do you know the steps to bias the newer style with 4 outputs per channel

 

[djk]

Same way, 100mA per output P&N output pair, plus 25mA for the front end

 

[jonnymyaudio]

I had a couple problems trying to bias the amp. My readings were all over the map. 1st I was using a cheap multimeter to try and measure ma and 2nd was my 4 100uf 100v caps had a lot of leakage. So I put new caps in and I got a real test meter for measuring ma and now it works like a charm. Thanks djk

 

[tony Ma]

Here what I got from the factory