Hifonics Zeus zrx-3000.1d Help!!!

[charles75212]

I meant 2SA1275 & 2SC3228. Sorry.

[Perry Babin]

They are probably the driver transistors. They act as a buffer between the driver board and the FETs.

[charles75212]

Hello Perry. I'm back. Here's an update. First, I fixed the problem with the amp only pulling .204 volts from the power supply. The solder pads on the driver transistors(2SA1275 & 2SC3228) were burnt pretty bad so I used a jumper wire to connect them. I discovered that I had the jumper wire in the wrong place. Once I corrected that problem, the amp powered up just fine and the relay did engage. Now, I replaced all the output transistors(IRF640N & IRF9640) and re-installed all the power FETS(IRFP064N) and the amp powers up just with no FETS overheating or failing like in the beginning. The problem I have now is when I connect a speaker to it, I only get a feedback\humming noise and that's with and without a signal through the audio input. I have positive & negative rail voltage(+/-24Volts) across the dual rectifiers and output transistors(IRF640N & IRF9640). Your assistance is greatly appreciated. Thanks.

[Perry Babin]

Do any of the controls on the amp make any difference in the hum?

Are you saying that absolutely nothing was connected to the RCA jacks?

[charles75212]

Hi Perry. When I increase the volume knob, you can hear the change of pitch if that makes any sense. And Yes, that's with and without anything connected to the RCA jacks. I actually have it powered up in front of me right now.

[Perry Babin]

Can you make the hum change if you push on the various pots?

Does it produce audio?

Don't check for audio unless you clamp the FETs.

[charles75212]

I have to admit Perry that I do not have any of FET's or output transistors clamped. These black clips are not that easy to take on & off all the time so I thought I could get away with testing for audio for a few seconds without them. I guess not. My bad.

[Perry Babin]

The clamps are only to reduce the chance of destroying the FETs. They should not affect the hum.

If you haven't seen THIS, it may help with the clamps.

[charles75212]

Cool. Thanks Perry. I'll pop the clamps back on and continue testing. Give me a few minutes and I'll see if the humming changes when I push certain pots.

[charles75212]

Ok Perry. I popped the clamps back on. I powered up the amp and I get still get the humming noise, so I decided to run a signal through it with my iphone on HBO and you hear the audio but it isn't clean. When I turn the volume up, you can hear the audio increase but it isn't clean at all. It almost sounds as if someone is underwater.