Can that 50v ac damaged the transistors?
Yes.
can you give me a scheme?pull out all semis and test them with simple matching jig
my led is not working can this give me an open?
http://www.firstwatt.com/pdf/art_mos_test.pdf
small bjts you can test with diode test on your DMM ; http://www.bcae1.com/
you can use 10R for in lower pic
use 9V battery for V
small bjts you can test with diode test on your DMM ; http://www.bcae1.com/
you can use 10R for in lower pic
use 9V battery for V
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Going back to biassing, the bias current wil not start to rise until the output FETs start to turn ON.
Once you have replaced the semis just trrying turning up the bias two turns at a time until the output FETs start to conduct. Then you can adjust the bias as necessary.
Once you have replaced the semis just trrying turning up the bias two turns at a time until the output FETs start to conduct. Then you can adjust the bias as necessary.
I've checked ztx450 and the hfe is circa 300 but it increases to 1000. I think it should be 100-300. Is it normal?
ztx are "just" current limiters , in case something goes south
besides that - it's either bad battery in your DMM or shitty DMM
that reading is , well , wrong
... The F5 really didn't like being biased at 3A (ish).
Obviously. I bet any other amp can take 3A per MOSFET with ease...
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