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Old 22nd May 2010, 09:55 PM   #1
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Cool Replacing Bias IC with Individual Transistors

So the MPQ6001 IC is 15 dollars on ebay with 10 bucks shipping and i need 2 of them. So needless to say i would be much happier just replacing this part with 4 independent transistors. If anyone had a few hints as to what transistors would do i would be grateful. I was thinking MJE15029G and MJE15028G. Here's the datasheet for the IC MPQ6001 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive. Thanks everyone! BTW- This is the Bias IC for a Son of Ampzilla.
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Old 22nd May 2010, 10:33 PM   #2
llwhtt is offline llwhtt  United States
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Using the data sheet you can check each of the 4 transistors inside, they are either good or bad. There 2 NPNs and 2 PNPs. Search this forum for the discrete transistors, I think Mike Bettinger from Gas Audio had the answer. 2N5551s and 2N5401s is what he suggested.

Craig
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Old 22nd May 2010, 10:36 PM   #3
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Great, i will look into that. Thanks!
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Old 22nd May 2010, 11:07 PM   #4
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If you bothered to look at the data sheet, you would see that the transistors are equivalent to the 2N2218 and 2N3904.
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Old 23rd May 2010, 03:29 PM   #5
djk is offline djk
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Unfortunately, companies cannot be expected to keep
> > manufacturing parts
> > forever, especially when the demand dwindles.
> > Regarding the GAS100A, it is
> > identically the same circuit that I also used in the
> > Sumo Amps and am still
> > currently using in my SST amps. Right now I'm using
> > a complementary pair of
> > TO-92 Darlingtons that are still available from ON
> > Semi. The circuit was
> > long ago made public. It is still the absolute
> > positive best thermal
> > tracking circuit ever created. If it ain't broke,
> > don't fix it.
> > James
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Old 23rd May 2010, 06:28 PM   #6
djk is offline djk
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Replace a bad GAS100A with a MPSA13 (EBC goes to 5,2,1) and MPSA63 (EBC goes to 12,9,8). They must touch the heatsink.
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