Help!! Are these power transistors interchangeable?

Mbira · Mar 28, 2006

I'm fixing a SWR California Blonde. It keeps blowing power transistors (and fuses). HERE is the schematic for the amp. Q7 and Q8 are the question. On the amp I have, there are c2837's (2SC2837?) and here is a datasheet for them:
http://www.datasheetcatalog.com/datasheets_pdf/2/S/C/2/2SC2837.shtml
The schematic calls for these:
http://www.datasheetcatalog.com/datasheets_pdf/2/S/C/3/2SC3264.shtml

These seem quite different to me, are they interchangeable?

Thanks very much for any input...

:guinness: [/url]

KingKai · Mar 28, 2006

Joel,

I think these are very close but for two very important specs for amplifier use. These two specs are Ic and Vceo. The Ic parameter for the 3264 is almost double the 2837 part. and the Vceo is more than double. Hfe is a littel better with the beefier 3264 as well 40 .vs. 30. All of this adds up to the 2sc3264 being a good replacement for a 2sc2837 but not the other way around.

Since the amp is frying the 2837's I would say they are not up to the demands of this amp. Perhaps if it was only played quietly only on sunday by a little ol' lady they would survive. But that aint what bass amps are for. :twisted:

I would also check both driver transistors to these outputs (q5 & q6) for shorts. When outputs fail, they often fail shorted which takes out the fuses and sometimes their drivers.

After replacing the outputs and checking/replacing the drivers, bring the amp up slowly with a variac and watch the idle currents of both outputs for weird or uneven currents. Also watch the rails for uneven voltage as they come up. This could indicate a pwr sup problem.

Hope this helps
Peace- Out
Irv

Mbira · Mar 30, 2006

Thanks Irv. I finally got the old schematic with the origional transistor. The others I ordered were the wrong footprint :? One thing after another...

Joel

KingKai · Mar 30, 2006

Yeah, It's a slippery slope for sure. :shock:

Keep us posted on how it goes for you.

Peace - Out
Irv

Help!! Are these power transistors interchangeable?

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Help!! Are these power transistors interchangeable?

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