Pioneer SX-950 Power Amp Mini Test

[cferry1]

Hello.

I am interested in rebuilding one channel of a Pioneer SX-950 Power Amplifier Board.
I would like to test DC 0 volt Balance and Bias Current when completed.

However, I would like to do in this in a two step process (First) with the Final 4 2SD427’s and 4 2SB557’s removed. (Second) with Final 2SD427’s and 2SB557’s installed.

Do you see any problem with this two step process ?

thank you for suggestions.
cferry1

 

[merlynski]

I usually use the 'two step process' as you call it, to test and troubleshoot many similar power amp architectures. The emitter resistors on the driver transistors close the DC feedback loop, so the dc offset adjustment will work, thus it can be tested for functionality. You cannot 'test' the bias current setting without the output transistors installed, as there is none - since it flows between the plus and minus supplies through the output transistors and their emitter resistors.
Build or acquire a DBT, it will save you time, money, and magic smoke: Dim Bulb Tester diagram pictorial... please feel free to copy and post.

 

[cferry1]

Thank you.

I agree about Bias Current Test, I assume , some fragmented memory, ( mine ) , from the last time , I was in such equipment.

I did a similar Two Step Process w/ a Pioneer SX-3900 and a SX-950 some time back !