Rockford Fosgate P300-1

[caraudioguy2100]

I replaced the outputs in this amp .

When powered up the amp will play distorted audio and play audio the cut off and play audio and cut off every time it does this the protection light flickers

Any ideas what might cause this

 

[Perry Babin]

Is it drawing excessive current?

Do you have both ± rail and regulated voltages?

 

[caraudioguy2100]

The amp ideals around 1 amp of current draw .
I get + - 45 volts of rail
I get + - 15 volts on all opamps

The bias pot has no affect on current draw so I believe it’s not working

 

[Perry Babin]

Is it remaining on long enough to reach the end of the initial mute delay? If not, the bias won't do anything.

 

[caraudioguy2100]

Yes it stays on long enough had it powered up for 5 mins idling and tried adjusting the bias and the pot has no effect .

It only flashes In and out of protection when playing audio

 

[Perry Babin]

See if you can get the diagram for the main board and the driver boards from Rockford.

 

[caraudioguy2100]

I found a bad source resistor that was overlooked .

With a bad source resistor could that be the reason it won’t bias or do I have another problem

 

[omni280]

I had a P500.4 with a similar problem, the 3W 0.1 ohm output mosfet source resistors went out of tolerance when the outputs shorted and were reading around 2 ohms. Replacing the resistors fixed the problem. Set the bias to 2mV per the schematic.

 

[Perry Babin]

It would take at least 2 open source resistors to stop it from biasing.

If a source resistor opened, there is a chance that the protection circuit was damaged. The low value resistors connected across the source resistors are the most likely to have failed.

Can you now bias the amp after replacing the source resistor?

 

[caraudioguy2100]

No it still won’t bias .

I will check the resistors now

 

[caraudioguy2100]

Replaced the resistors since they were out of tolorance .

Same problem still won’t bias

 

[Perry Babin]

What does the output waveform look like?

 

[caraudioguy2100]

Wave form looks normal .

But I get distorted output for some reason the amp will not bias

 

[Perry Babin]

Generally, if it's badly distorted, it's clearly visible on the scope. If it's in the heatsink, drive it hard into a load and see if it clips symmetrically.