Need Help With BUZ901/906 MOSFET Amplifier

[ridikas]

Solved.

[lineup]

Sounds as you have vert bad bias.
There should be one little potentiometer somewhere close to the MOSFETs or a bit from them in the middle.
You should adjust this potentiometer so that you get some current warming the MOSFETs up.

[ridikas]

The bias is via a fixed resistor, 270 ohms. I've tried a 470 ohm resistor. It more than doubled the gate voltages, but the results were identical, distorted sound and not even warm to the touch, even if touching the body of the MOSFET directly.

[lineup]

Strange.
Because the 470 Ohm resistor should be enough.

[lineup]

I think you better check those mosfet.
Setup a little circuit, take them away from heatsink and do some testing.

[ridikas]

Originally Posted by lineup

Strange.
Because the 470 Ohm resistor should be enough.

That's what I thought too. I'm a little baffled. Is there any chance that either the power caps, or the MOSFETs are bad? That would mean that all 4 MOSFETs in each of the two channels are bad, because none of them are warming up.

[moschfet]

Show us the circuit and maybe we can find out whats wrong

[cjkpkg]

You need like 3vdc on the gates to get the buz to bias up.