Hey, Ive built a couple of Pass amps, the Zen 4 and the Zen (light bulb)
The Zen 4 id had working for a year then accidently messed with the interconnects while it was on and i guess it must have sent a buzz to the input buffer then somehow blew 3 of the mosfets too!, it was lovely while it worked tho!
Then just recently i built the Zenlightenment and had 500w bulbs on it worked fine with the 250w, i expect i had the bias too high or something and fried one of the mosfets (should have had a multimeter to check voltages at the time!) other channel biased up and is fine!, anyway i know those IRFP240 and 140's are a bit senstive so i ask here is there any way of protecting those fets sensitivty while experimenting with the amps ? i know ive heard of putting in Zener Diodes on the gates of the Mosfet but not sure how to do that.
If anyone has any good ideas let us know 🙂
Those Mosfets are pretty expensive realy so it would be nice to not blow any more up!
The Zen 4 id had working for a year then accidently messed with the interconnects while it was on and i guess it must have sent a buzz to the input buffer then somehow blew 3 of the mosfets too!, it was lovely while it worked tho!
Then just recently i built the Zenlightenment and had 500w bulbs on it worked fine with the 250w, i expect i had the bias too high or something and fried one of the mosfets (should have had a multimeter to check voltages at the time!) other channel biased up and is fine!, anyway i know those IRFP240 and 140's are a bit senstive so i ask here is there any way of protecting those fets sensitivty while experimenting with the amps ? i know ive heard of putting in Zener Diodes on the gates of the Mosfet but not sure how to do that.
If anyone has any good ideas let us know 🙂
Those Mosfets are pretty expensive realy so it would be nice to not blow any more up!
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The zener at the gate only protects gate. Normally, you can put a zener cathode to the gate (For N channel) and anode to source (not ground), also you can add a second diode in reversal series with it, to protect in case of -VG. But although zener is in the circuit, short circuit at the load or VDD >> VDSS the fet also will be destroyed.
Download GX400 rev.1 project here:
GX400 rev.1 - 400W Audio Amplifier - Comunitatea Tehnium Azi
In that project you will find in amplifier diagram a MOSFET transistor protection circuit. It is one of the best short-circuit protection circuit on the output audio amplifier.
GX400 rev.1 - 400W Audio Amplifier - Comunitatea Tehnium Azi
In that project you will find in amplifier diagram a MOSFET transistor protection circuit. It is one of the best short-circuit protection circuit on the output audio amplifier.
use an in series ~60 w light bulb in supply line as a current limiter, a variac would be nice to bring it up slowly to help you find the real culprit. o/p trannies when they go usually take a driver with them....hafler dh200 thread has a great section on starting a bad amp up to troubleshoot.
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