Oscillations in P3A ??

Stormo · 16th January 2003, 09:03 AM

Pls help !

I have build several versions of P3A and they where fine. I have now a +/- 42 volt version and it is oscillating very hard - 20 volt p/p probably in the Mhz area. All caps ara mounted but nothing helps. What to do ? the output is 2SC3281/2SA1302.
Btw, if i drive it hard (input 2v p/p) @ 1 Khz it stops oscillating and act OK.

trwh · 16th January 2003, 09:41 AM

Hi

Are you sure your output devices aren't fakes? The 2SC3281/2SA1302 parts you mention were discontinued some time ago. Check here:

Toshiba 2SC3281/2SA1302 - Are these fakes?

Stormo · 20th January 2003, 07:58 AM

Thanks for the advice, but still i think the design shoul work.
Can anyone explain ??

I am kind of desperate.

Mattyo5 · 20th January 2003, 09:34 PM

Have you contacted Rod Elliot about it? It does sound to me like those chips need to be replaced. I don't know about where you are, but here, Digikey has the new Toshiba chips for like $2 each. The 2sc5200 and the 1943? Cheap enough. Contact Rod Elliot and let us know what he says about it.

-Matthew K. Olson

16th January 2003, 09:03 AM	#1
Stormo diyAudio Member Join Date: Sep 2002 Location: Denmark	Oscillations in P3A ?? Pls help ! I have build several versions of P3A and they where fine. I have now a +/- 42 volt version and it is oscillating very hard - 20 volt p/p probably in the Mhz area. All caps ara mounted but nothing helps. What to do ? the output is 2SC3281/2SA1302. Btw, if i drive it hard (input 2v p/p) @ 1 Khz it stops oscillating and act OK.

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16th January 2003, 09:41 AM	#2
trwh diyAudio Member Join Date: Apr 2002 Location: UK	Hi Are you sure your output devices aren't fakes? The 2SC3281/2SA1302 parts you mention were discontinued some time ago. Check here: Toshiba 2SC3281/2SA1302 - Are these fakes?

20th January 2003, 07:58 AM	#3
Stormo diyAudio Member Join Date: Sep 2002 Location: Denmark	Thanks for the advice, but still i think the design shoul work. Can anyone explain ?? I am kind of desperate.

20th January 2003, 09:34 PM	#4
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Have you contacted Rod Elliot about it? It does sound to me like those chips need to be replaced. I don't know about where you are, but here, Digikey has the new Toshiba chips for like $2 each. The 2sc5200 and the 1943? Cheap enough. Contact Rod Elliot and let us know what he says about it. -Matthew K. Olson

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