Had a very badly arched amp come in for repair. One whole side of the amp section was burnt. Pulled all the output fets and audio driver card. This amp has a drive circuit for the gate driver. All the BTJs were shorted. Replaced them. Replaced the ir21844 on the one side that was blown(driver card only has two shown in picture below). Replaced a small resistor on the card as well. Also replaced all the 1 ohm resistors in the gate drive circuit. Problem is i still have no low or high side drive wave with fets reinstalled.(only 1 per bank). Also had to replace all the gate resistors. Can anyone identify U6, U4, U3 on the card? The amp died a bad death.
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Yes i did test with no fets. and also applied a signal to see if that might bee the case. I know some amps wont have drive without a small signal.
All 21844 voltages except for the 3 high-side terminals will be measured with the black probe on the negative rail terminal. The low-side shunts are an easy location to place the black meter.
Do NOT ground your scope to those shunts unless it's a battery operated scope with no connection to the mains.
Do NOT ground your scope to those shunts unless it's a battery operated scope with no connection to the mains.
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Well I am back working on this amp. Looked it over for a solder bridge and anything else i might find. The muting transistor is a D1302. I cant find anything that might be a replacement for it. Any ideas? I found a ktc3200 might be but cant seem to find it at mouser. Found a used one on another amp and replaced it. when I did that it went into protection twice but then it failed. Dont have any others to try.
I also replaced all the ICs on the audio board just to be sure it was fresh.
Thanks in advance
I also replaced all the ICs on the audio board just to be sure it was fresh.
Thanks in advance
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