Hello friends! Thank you for allowing me to continue being part of the forum. On this occasion I have in my hands an amplifier of the brand Mtx model 81000d in which I received an irf540 in the output stage, of course it was blown up. The problem is that it does not generate audio. LEDS 399 and 463 turn on, but there is a current consumption of more than 4 amps and the fet that is attached to the board is very hot, I have a sawtooth gate pulse, but I understand that it is normal, at least Turn on the amplifier my supply voltage goes from 12v to 9v, I checked the fet that is on the board and it reads well, tomorrow I will lower it and get the HCPL3120, in the same way I measured them and they seem to be fine but I will try to get them, thank you your help and patience... regards
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The FET on the board should only heat up if you repeatedly power the amp up, them down.
Do you have ±15v on the power supply terminals of the op-amps?
What's the DC voltage measured directly across pins 5 and 8 of the two 3120s?
Do you have ±15v on the power supply terminals of the op-amps?
What's the DC voltage measured directly across pins 5 and 8 of the two 3120s?
the fet on the board gets hot from the start, you can even feel it when you run your hand. In the operationals TL072C and NE5532 I have pin 4 -15.54v and pin 8 16.28, only the 3845A has pin 4 2.43v and pin 8 5v. In the 3120 there are 19.90v and 18.14.
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Copy and paste the following list and fill in the blanks. If there is no blank space after the colon, add one between the colon and the numbers you enter. I makes it much easier to read.
All voltages on the LM339:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
All voltages on the LM339:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 1: 4.038
Pin 2: 4.046
Pin 3: 8.20
Pin 4: 4.95
Pin 5: 4.978
Pin 6: 2.616
Pin 7: 4.953
Pin 8: 4
Pin 9: 3.356
Pin 10: 0.734
Pin 11: 3.356
Pin 12: 0.016
Pin 13: 4.120
Pin 14: 0.023
Pin 2: 4.046
Pin 3: 8.20
Pin 4: 4.95
Pin 5: 4.978
Pin 6: 2.616
Pin 7: 4.953
Pin 8: 4
Pin 9: 3.356
Pin 10: 0.734
Pin 11: 3.356
Pin 12: 0.016
Pin 13: 4.120
Pin 14: 0.023
Do you read low resistance between terminals 6/7 and 8 or 6/7 and 5 for either 3120? No power applied?
I do not read low resistance from 6/7 to 8 170kohms and increasing, from 6/7 to 5 4500kohms in both
Remove them and clean the pads so there are no bridges between pads.
Will the amp power up with LED238 lit up?
Will the amp power up with LED238 lit up?
There are two errors:
First: Gate signal MUST be square or rectangular, not a sawtooth.
Second UC384x has power at pin5 (gnd) and 7 (VCC). Pin6 is the output, 8 is a 5V reference, 1 and 2 the error amp output and input respectivelly qnd pin 3 is the current sense. Pin 4 is the oscillator.
First: Gate signal MUST be square or rectangular, not a sawtooth.
Second UC384x has power at pin5 (gnd) and 7 (VCC). Pin6 is the output, 8 is a 5V reference, 1 and 2 the error amp output and input respectivelly qnd pin 3 is the current sense. Pin 4 is the oscillator.
You are right, on pin 6 I get a square signal 7 vcc, 4 there is another signal, 5 gnd, 1 and 2 I get nothing
The 3845 is doing it's job. It's driving the transformer near it and, after rectification, is producing the various low voltage supplies.
If that scope is completely isolated, check the waveforms on the gates of the high and low-side FETs. This is best done with a loading capacitor (~0.01uf) connected across the gate and source.
If that scope is completely isolated, check the waveforms on the gates of the high and low-side FETs. This is best done with a loading capacitor (~0.01uf) connected across the gate and source.
English, please.
With no output FETs, drive a signal into the amp. What signal do you see on pin 7 of the 5532 near LED238?
With no output FETs, drive a signal into the amp. What signal do you see on pin 7 of the 5532 near LED238?