So I had to wait for a few things to come in and also have been quite busy here lately. I ordered a Mega328 transistor tester (and a desolder pump) and retested the output transistors. I'm trying to withdraw from applying voltage as long as I can.Enzo wrote:Cap can easily have been damaged running backwards. But I just bring up the voltage and find out. A shorted cap might blow fuses, but won't stres the transistors.
No load on the amp output, and look up "light bulb limiter" and make one and use it.
I replaced the original SJ6357 with Peavey's suggested MJ15003. The SJ6357's being discontinued and near impossible to get your hands on. Now to my understanding from the .PDF datasheet here: https://www.onsemi.com/pub/Collateral/MJ15003-D.PDF
The hFE rating for the MJ15003 transistors should be min=25 max=150. I got the following readings using my tester:
#1 hFE=57 Uf=563mV
#2 hFE=62 Uf=563mV
#3 hFE=67 Uf=563mV
#4 hFE=41 Uf=558mV
#5 hFE=57 Uf=558mV
#6 hFE=57 Uf=558mV
#7 hFE=32 Uf=553mV
#8 hFE=74 Uf=559mV
To me this looks like a missmatched set of transistors. Maybe your more professional mind can explain this. To me it looks like #4 and especially #7 is way off balance.
I also tested the main capacitors with my tester. They tested ok. One being right below 5000uF, the other being at or slightly above 5000uF. So those are good and in the correct position.
On top of this I tested the 3 audio transistors. The results are as follows:
JE243G OFF HEATSINK hFE=124 Uf=632mV
JE243G ON HEATSINK hFE=145 Uf=628mV
SJE5332 ON HEATSINK hFE=141 Uf=618mV
JE243G being Peavey's recommended replacement for SJE5331. Another discontinued transistor. I could only find the datasheet for JE243G, which is here: http://pdf1.alldatasheet.net/datasheet- ... E243G.html According to my knowledge, the hFE should be min=40 max=180.
This is starting to confuse me as all of these should be functional in their current state, with minor questions. I have checked to make sure that neither of the two audio transistors are touching their heatsink, causing a short.