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seankane 6th January 2012 11:28 PM

Rockford Fosgate Power 800.4
I need a schematic for this amp, the board number is PC-3095-A.

Doea anyone have one?

josesony68 7th January 2012 01:00 AM

Sorry, but I do not know if it will or not ....

seankane 7th January 2012 03:56 AM

Its got to be close enough, thank you very much!!

This amp was stripped and used for parts and I am trying to revive it it.

So far everything is a go but I have one issue.

Q123 and Q110 read OL from gate to source testing with my meter.

Various components were missing and I have replaced alot of SMD components. These are the only two output fets that read this, the rest check out fine.

There must be something open or faulty somewhere just not sure where to look.

Hoping someone can steer me in the right direction.

seankane 7th January 2012 05:59 AM

I cannot seem to get the -36.50 vdc off of the left front channel and it wont bias either.

All other channels will bias and produce clean audio except the left front.

josesony68 7th January 2012 09:24 AM

Maybe, I'm not best placed to help you, but I can give you some idea as to help you ..

Q110 and Q123 If (IRF540) you get 0 on the meter, must be short, and you have to replace them.
You should also review, Q121, Q122, and D106, for just in case, they were wrong, or leaking, (is what I would do ...)

I repaired a, 700S and 851X, which are very similar to that you have.

seankane 7th January 2012 09:53 AM

Yes thanks for the advice but all those have been changed because they were missing. Every smd diode and transistor in that area is brand new along with all of the outputs. I must have an open or out of tolerance resistor somewhere to get the 36 vdc on the left front bridging terminal.

Not really sure where else to look??

josesony68 7th January 2012 10:59 AM

So .... Have you Q110 and Q123 is also changed? and do you still gives 0 on the meter, after being replaced?
That's odd ..
If these transistors are short, it is normal to have 36v at the output of audio ...
There must be wrong, something more ..
I do not think that tolerance of the resistors is the cause of this failure.
Do not know what else to tell you, sorry.

Perry Babin 8th January 2012 12:36 AM

What's the resistance from the gate of Q110 to the emitters of Q121 and Q122?

josesony68 8th January 2012 09:19 AM

I think it's
R135, its value is 20 ohms, tolerance 5% (Format: smd 1206)

seankane 10th January 2012 02:12 AM


Originally Posted by Perry Babin (
What's the resistance from the gate of Q110 to the emitters of Q121 and Q122?

From the gate of Q110 to the emitter of Q121 is 40.1 ohms

From the gate of Q110 to the emitter of Q122 is 40.1 ohms

They are both the same.

One thing to mention its hard to tell because they are so close together but Q100-Q104 all or some of them are getting VERY hot.


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