Hello, newbie looking for some suggestion on resurrecting my old Class A/B amplifier after a catastrophic failure.
Here's the tale, so for the best of my luck when I was checking the bias mA on my Samson S700 amplifier for note them down as maintenance routine, somehow when I powered the amp the test alligator clip slides from the output emitter pin touching other pin or the nearest resistor and I quickly turned the unit off after a smelly big smoke cloud, this is the first time this silly thing happens to me tbh, really frustrating situation.
Now the amp channel 1 module has two failed transistors one pair 2SA1492 / 2SC3856, two small 1/2W burned base resistors, tree open/burned 0.47ohms 5W emitter resistors and the unobtanium
2SJ78 / 2SK215 lateral MOSFET's.
😱
Since there is no 2SC3856 avail at Mouser, Newark nor Digi-Key and since eBay is full of fakes to bother with, I opted for all the pair 2SA1943N / 2SC5200N(2SA1386A/2SC3519A was pricey) as I've read some threads users using them as replacements and they are a tad better, also listed by the NTE as replacement too.
So I ordered all the parts, 6 pairs 2SA1943N / 2SC5200N and the silicon thermal pads, all the small base/emitter 1/2W resistors, all 12x 0.47ohms 5W emitter output resistors.
However I'm now stuck at trying to find 2 pairs 2SJ78 / 2SK215(or 2SJ79/2SK216) lateral mosfets from any reputable sources to no avail, and the ones I've found under the U.S. location are a bit pricey for being NOS parts if that's even the case.
😒
All this frustration made me spent lots of time searching/compare for those laterals mosfets and I almost to execute an absurd experimentation, just replacing the 2SJ78 with ->
ECX10P20 and the 2SK215 with ->
ECX10N20, I know those laterals are way overkill for the role of pre-drivers but I could not find anything similar in the case TO-220 unfortunately.
🤔
So the question is, after re-biasing the amp does this big laterals can work as drivers in place of the unobtanium/obsolete 2SJ78 / 2SK215, and what could be the drawbacks of using such large/overkill laterals instead the smaller with less input capacitance, I guess the amp may be prone to oscillation at high frequencies and/or lower amplifier gain? assuming this overkill laterals can work as drivers of course.
Also is there another/better 2SJ78/2SK215 replacement candidates with similar specs regardless of the gate/drain pin configuration, I'm up for options/experimentation.
Amp channel modules cleanup/preparation started:
Regards