Well just a quick update, got the new gate resistors and the 3205's put in... Powered it up thru a fuse. The power light would pulse off every 5 seconds or so then my fuse blew about 20 seconds in. Didn't get a chance to measure any voltages. The heat sink on the power side warmed up a bit nothing smelled or felt hot after the fuse blew. Thinking I might pull the outputs and see if maybe they are bad after all. Also going to check the power side to see if they were damaged before the fuse blew
Had a few minutes this morning to take some measurements and it appears that the 4 fets nearest the rectifier diode are shorted. All the gate resistors still measure fine and the 4 fets to the other 4 fets further down in the group of 8 still measure fine. Any pointers on what I should focus on that would have cause 4 of the 8 to shortout?
Did all 4 of that groups short or only 1?
A defective driver transistor, a bad solder connection or a broken trace could cause the FETs to fail.
Did you have them tightly clamped to the heatsink with heatsink compound applied to both sides of the insulator?
What size fuse?
What power source when testing?
A defective driver transistor, a bad solder connection or a broken trace could cause the FETs to fail.
Did you have them tightly clamped to the heatsink with heatsink compound applied to both sides of the insulator?
What size fuse?
What power source when testing?
They had compound/insulators and were clamped. Power source was a car battery @ 12V, and the fuse was a 20amp... Lost my 10 amp fuse I had sitting around. All 4 in the group failed . When the amp was originally disassembled it was the other 4 that looked the worst. When these failed they didn't appear damaged unlike the originals that blew up explosively apparently
I'll go back and check the solder with a 10x loupe and see if anything looks outta whack. I didn't see anything solder wise before I powered up that would be an issue though.
I'd guess there is not a reliable test for the drivers without having a oscope to check the wave form.
I pull out the 4 failed and replace and double check everything visually and with a meter to see what I get.
Generally, if the DC voltage measured on the emitter of the driver transistors is relatively reliable. If the voltage is the same or very nearly the same for both pairs of drivers and below about 6v DC, the drivers are likely OK.
so, fets pulled there was one bad that caused them all to read shorted. I didn't see anything out of the ordinary with the solder when removing them. Should I replace the group of 4 or should they be ok for testing with the shorted one replaced?
I swapped out the group of 4 and probed around with the meter. I didn't find any solder bridges or open connection. Tried powering up again... Checked the voltage at the 3 leg on the driver transistors and it slowly climbs to about 3 volts them drops back to 0. The amp blows a 10 amp fuse after a few seconds. Is it possible for the diode to fail with out looking damaged?
did you perform diode check before?..
if no, go check it.if yes, and didn't find any damaged diode, there's another problem..
i would recommend you to remove the diodes before measuring for accurate result
if no, go check it.if yes, and didn't find any damaged diode, there's another problem..
i would recommend you to remove the diodes before measuring for accurate result
Yeah, probably should have started with the obvious thing seems how the power fets were roasted and the outputs were fine... Checked the diode and one side is a dead short and the other is open... Any thoughts on anything else to check that could have failed because of the diode or it shorting and taking out the power supply pretty much the end of the line?
Looking at the data sheet for the sf1606g it looks like it's a 400v, 16amps, 35ns recovery, does the replacement need to have such a high voltage withstanding? Or is something around 250v and 20 amps sufficient?
Is there a trick to finding stuff on digikey? I looked and didn't see this earlier. Only way I find this on is typing in the part number.
I don't think that there are any quick shortcuts. I've been using the suggested rectifier for about 20 years. The negative version is the MUR1620CTRG. They make good subs for TO-220 case rectifiers in amps that have less than ±100v of rail voltage.
I've put about an hour worth of use on this amp and i've noticed the transistor just under the small transformer is pretty warm.
First I was wondering if that is fairly typical in this amp to have this transistor run warm?
Second it looks like there are some small led's on the main board. should any of these be illuminated during normal operation of this amp?
First I was wondering if that is fairly typical in this amp to have this transistor run warm?
Second it looks like there are some small led's on the main board. should any of these be illuminated during normal operation of this amp?
That transistor operates at relatively high temperatures. That's normal.
No. Those LEDs won't be lit under normal operating conditions.
No. Those LEDs won't be lit under normal operating conditions.
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