Rockford Fosgate Punch 600a4

Perry Babin · 2021-03-20 6:55 am

DC voltage on pin 4 of the 494 with Q9 out of the circuit?

objext · 2021-03-20 6:59 am

So, something wrong with the 3rd channel (left rear) perhaps?

objext · 2021-03-20 7:02 am

494 Pin 4: 0.099v, Q9 still out.

I feel like I should lift R370 as the negative voltage is coming across it from the 3rd channel. I will resume looking at it tomorrow. Thanks Perry - very kind of you to help with all this!

Perry Babin · 2021-03-20 7:33 am

I'm a bit confused as to how you have negative voltage with no voltage on the gates of the PS FETs?

Do you see rail and regulated voltage in the amp?

Is it possible that the amp is coming on for a fraction of a second and charging the caps?

Sure, pull the resistor.

objext · 2021-03-21 12:05 am

I lifted R370 only to realize I have negative voltage on every channel at this point. I have negative voltage on the LM317 output & adj it looks like.

Perry Babin · 2021-03-21 12:09 am

Do you have negative voltage on the output of the positive rectifier?

objext · 2021-03-21 12:19 am

LM317
In: 30.43
Out: -1.771
Adj: -1.947

LM337
In: -29.44
Out: -17.30
Adj: -15.97

objext · 2021-03-21 12:23 am

D8? Looks like positive 30v, and D9 about -30v

Perry Babin · 2021-03-21 12:29 am

It looks like the LM317 is open (defective). Check the value of the programming resistors on it.

objext · 2021-03-21 12:37 am

R32 & R35? They appear to be in range.

Perry Babin · 2021-03-21 12:38 am

Yes, 32 and 35.

objext · 2021-03-21 1:11 am

I'll swap out the 317. The solder joints look bad on it also. I've come to not love this model with the regulators out in the middle uncoupled from the main heatsink...

objext · 2021-03-22 12:52 am

Replaced the LM317 and now have clean audio from all channels. I was expecting higher voltage on the power supply mosfets (it's around 0.9v). Does that seem normal? The LM317 was running at about 160°F, which is at least quite a bit lower than the other I have that runs up to 210°F

Perry Babin · 2021-03-22 1:02 am

What's the rail voltage in this amp and the other one?

Are you referring to the gate voltage on the PS FETs?

objext · 2021-03-22 1:14 am

Yes, gate voltage on the power supply fets. I will have to get them out again to check the rail voltage.

Thanks for getting me going in the right direction

Rockford Fosgate Punch 600a4

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