Wednesday 6 September 2017

Testing an Audio Power Amp with Paralleled Transistors


A question concerning my current repair project of an audio amp that uses big (600 W) but otherwise rather classic complementary output stages:


I assume when testing an audio power amp with 6 pairs of paralleled npn/pnp transistors, it is o.k. to assemble just 1 pair while testing as long as you have no significant output load connected. The advantage would be that, while testing, I would not blow as many of the precius MJ15022/23 transistors I have available as spare parts.


In what ways (if any) will the bias current circuit be affected?


Any problems I may not have considered but may be important for this repair technique?


Any other really good tricks for fixing big amps?


Once I am closer to finishing the repair: Does 10...15 mA of bias current per transitor branch sound like a good number to you?



Answer



1 bank of 6 at a time ok. Bias not affected significantly. 10-15 mA plausible.



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