How can a 70484200 Silicon test as Germanium? - diyAudio
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Old 8th November 2012, 01:39 PM   #1
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Default How can a 70484200 Silicon test as Germanium?

Hello,

I am working on a Peavey CS-1200 amp. On one output channel, 2 out of 7 70484200 Silicon NPN output bipolars, test as a germanium not a silicon! The only notable difference in parameters was the Hfe of 14 and 17, while the other 5 ranged from a Hfe of 19 to 27. The other test measurements appears to be similar if not the same. I am using a Peak atlas DCA55 analyzer.

What is going on? Should replace them? How important is Hfe in Peavey's CS amp series output circuitry?

Thanks,

Billy
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Last edited by grievousangel; 8th November 2012 at 01:42 PM.
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Old 8th November 2012, 11:28 PM   #2
Enzo is offline Enzo  United States
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The 84200 is just an MJ15024 with a house number on it. Peavey does not match power transistors.

If they show low junction voltage, then they are bad and should be replaced. It isn't germanium, it is very leaky junctions.

Always check the fractional ohm ballast resistors associated with each transistor.


Here is the master cross reference from Peavey
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File Type: pdf PV Semi Cross Ref 2009.pdf (96.6 KB, 12 views)
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