Does anybody know the value of R172 on this amplifier? I can tell it’s part of the pwm circuit for the gate drive. I think it’s a 10 ohm resistor but when I replace it I get the powersupply to operate and rail to rail oscillation on outputs then the resistor instantly starts smoking and separates. I pulled the buffer transistors and irf44’s to confirm they are not shorted and even replaced the 9942 out of a working amp to confirm they aren’t bad. A schematic would be better but I know there probably isn’t one. I took out the rectifiers also to separate the powersupply from output section and R172 still smokes.
I'm not really familiar with this version. How is R172 used in the circuit?
Is it in series with the cap and something that they are feeding voltage to shorted?
Is it in series with the cap and something that they are feeding voltage to shorted?
Yes, it’s in series with the postive terminal of the cap and feeds a pair of 1k ohm resistors that connect to the buffer transistors. It appears like this circuitry is used to feed the pwm to the 9942 driver IC’s but I checked everything outside of the board with a transistor tester and dmm and it was good.
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Do you have an incandescent lamp that you could install in place of that resistor to see if something is heating up?
Is this possibly a 3-layer board?
Is this possibly a 3-layer board?
Is the output voltage from the rectifiers too high for the capacitor?
Are you saying that you have no sort of lamp/bulb with a filament?
Are you saying that you have no sort of lamp/bulb with a filament?
The output voltage from the rectifiers is 12 volts. The capacitor is 50v 1000uf rated. I probably do have a lamp just have to search for one. Our bulbs are predominantly led.