MTX 1501D problem power supply


2016-01-17 2:57 pm
Hey there

I'm new to the forum. I hope to help and contribute as much as possible .

They have an amplifier MTX 1501D , which would have replaced the transistors of the power supply by IRF1010E , since according to the datasheet , are of better performance than the 75339p . IRFB42N20D are disconnected.
The amplifier turns on well but the coil of the power supply is noisy , and LED 399 is on, the LED 238 is off.
U1540 voltage is approximately 75V .

Why the power supply coil sounds ?

Thanks and Regards.


2016-01-17 2:57 pm
Sorry, it is my fault

Tensions are output transistors.

Fet: 255, 256, 257, 258. Gate: -75V, Drain: 0V, Source: -75V
Fet: 245, 246, 247, 248. Gate: 0V, Drain: +75V, Source: 0V
FET 260, Gate: -58V, Drain: 0V Source: -58V
FET 327, Gate: -75V, Drain: +75V, Source: -75V

A3120 voltage obtained:

Side capacitors 1000UF: legs 1-4: 0V - leg 8: -58,4v, leg 7: -75v, leg 6: -75v leg 5: -75v
IC capacitors 3300uf side:
legs 1-4: 0v - leg 8: + 0.1v, leg 7: 0V, leg 6: 0V, leg 5: 0V