Rockford Fosgate Power 1000a2

[seankane]

If the source leg isn't at ground, you have an open trace.

Sorry I was not thinking, looking at the mosfets backwards. The gate and drain have 13.87 vdc, but the source reads 0.00 vdc.

Just dont understand why the faulty channel has no rail voltage.

 

[Perry Babin]

The FETs have failed. With 13v on the gates and drains and 0v on the source, the amp should be drawing excessive current. Since it's not, the FETs have opened drain-source. I'd expect that the gate resistors are open and it's possible that PNP gate drivers are open.

 

[seankane]

The FETs have failed. With 13v on the gates and drains and 0v on the source, the amp should be drawing excessive current. Since it's not, the FETs have opened drain-source. I'd expect that the gate resistors are open and it's possible that PNP gate drivers are open.

Why does the amp still power on, powering from the other power supply on the other channel?

 

[Perry Babin]

Yes.

 

[seankane]

Next question I will be using IRF 3205 as a replacement for the MTP75N05HD. Do I have to replace both power supplies or will the 2 different fets be ok since they are different power supplies, because the other side will still be the MTP75N05HD?

 

[Perry Babin]

The supplies are independent so you don't need to replace the ones in the other power supply.

 

[seankane]

Cool so you also said that more than likely the mps 6521 is bad too?

 

[Perry Babin]

That transistor is used for biasing. The driver transistors are the SMD transistors (four in a row) near the 494 for the power supply that failed.

 

[seankane]

Yes that is always standard replacement for power supply repair in a Rockfrod amp, I always do them needed or not. Thanks Perry.......

When I am finished with the repair I will let you know the outcome

 

[seankane]

Hey Perry using your advice on the 47 ohm gate drive for the power supply fets, as I have always used 68 ohm and NEVER had an issue. You are the expert so I am giving the 47 ohm gates a try. The only reason I used 68 ohm in the past is many rockford amps I pulled apart in the past that had IRF 3205 from the factory always had the 68 ohm gates. I remember reading in one of your posts that it could work but it seemed a bit high to you. I thought i remeber you saying that something could mask the problem at idle................

Got the new p/s fets in place......gate drivers are in.............driver transistors are in..........my only problem is when I test the 47 ohm gates I have in or out of the circuit they range from 45.6 ohms to 46.6 ohms.

Just wondering if this is within spec?? They are brand new parts.

Want to be sure before applying power.

 

[Perry Babin]

Those are within tolerance if they're 5% resistors (±2.35 ohms).

 

[seankane]

Again and Again Perry your knowledge amazes me. The amp is up and rocking on the bench it sounds awesome.............

Thanks so much you the man !!