Rockford Fosgate power t1500-1bd no output Help

[rhempz01]

I desperately need help with repairing this output section. Q200-Q2012 all have the correct voltages. No shorted outputs or power supply fets.

 

[Perry Babin]

Do you have R-R oscillation on all of the FETs in the output section?

 

[rhempz01]

Should I test the center legs of the fets for voltages? Or where should I be grounded to see the r2r osilalation?

 

[Perry Babin]

Why didn't you just probe ALL of the legs? It would have been quicker than waiting for a reply.

For virtually ALL testing for car audio, you can leave your scope grounded to the ground terminal of the 12v power supply. I almost never even have the ground lead on the scope probe.

 

[rhempz01]

I did, I just want seeing anything so I wasn't sure if it was because of a certain ground point. If I test between the 2 recifiers I get -71.1vdc.

 

[Perry Babin]

These amps don't have a floating secondary so the primary ground is good for most tests. For tests without the rectifiers, you may need to ground the probe to the source leg of the outputs but that's not yet necessary.

Do you see a square wave on any of the terminals of the two driver ICs in the output section?

Does your amp use the 8 pin or the 16 pin driver ICs?

 

[rhempz01]

8 pin, lm5110? No square wave, this is pin 4.

 

[rhempz01]

P4

 

[rhempz01]

The white block 3k 5w resistors, get to hot to touch.

 

[Perry Babin]

That's because it has rail voltage across it. That's normal.

Are any of the ICs on the BD driver board heating up? If you can't tell, freeze them with component cooler or inverted 'canned air' to see if one defrosts quickly.

 

[rhempz01]

None are over 93F

 

[Perry Babin]

Do you have any component or 'canned air'?

 

[rhempz01]

Have some on the way. I just noticed that a single power supply mosfet is heating up q1000, drive signal lokks perfect?

 

[rhempz01]

Pic2

 

[rhempz01]

sorry the last post was not for this thread. So as far as the power supply fets heating up. That would be a drive fault correct?

I have the compressed air now as well.

 

[Perry Babin]

Assuming that you replaced or at least checked the gate resistors, I'd say that a single PS FET heating is due to a lower turn-on threshold. You could swap positions with another FET to see if the heating follows the FET.

If you invert the canned air and spray the components on the driver board, they will freeze and frost over. When the ones you sprayed are white, power it up to see which defrost more quickly than others This will sometimes lead you to a defective IC.