Rockford Fosgate Prime R300X4

[cajones65]

Hi guys, I have this amp on the bench. It is in protect, but I can't find why. There are no shorted outputs or power supply FET's. The 494 pins 1 & 3 have a fluctuating voltage. Pin2 is at 3.7

 

[Perry Babin]

Are any of the outputs heating up when the amp is pulsing? Monitor the temperature of all of the heatsink mounted components while checking this.

 

[cajones65]

No the outputs are not heating up, but the power supply FET's are.

 

[Perry Babin]

Only connect ground and remote (no B+) and look at the drive signals on the gates of the FETs. Are the drive signals OK?

 

[cajones65]

Don't have no signal on the gates, or pins 9 and 10 of 494. Don't even have 12v on pin 12 or 5 volts on pin 14 without B+ hooked up

 

[Perry Babin]

They have been having that feature for 30 years. Its sad if they lost it.

Do you have a current limiter for your 12v supply?

 

[cajones65]

I do, this one is of only 3amps. I am trying to trace from the remote to the 494 now.

 

[Perry Babin]

This is a prime amp, it's likely just some chinese type amp.

Do you have a large 2 ohm current limiting resistor or similar? The resistor produces more consistent results.

 

[cajones65]

I am at work, so I don't have a large 2ohm resistor. I will look in the instrument shop.

 

[cajones65]

Perry I have a 10ohm 10w, will that do the trick? Or is it too much?

 

[Perry Babin]

Too high. 5 in parallel would work.

 

[cajones65]

3.3ohm 5 watt?

 

[Perry Babin]

Maybe. Ideally, something like a 2 ohm, 100w cylindrical wirewound is preferred. Order one the next time you order parts. You can also use it as a moderate power dummy load with fan cooling.

 

[cajones65]

I do have 5 of them at home, will have to bring a couple to leave here at work. Plus I have a couple of 4 ohm 1000w I use for testing a finished amp (dummy load).

 

[Perry Babin]

Use the two dummy loads in parallel.

 

[cajones65]

With that resistor in I am getting a flashing red to blue led.

 

[Perry Babin]

Is it staying on long enough to check the PS drive signals?

 

[cajones65]

Its trying to make a sq wave. Pulsating on and off. Very hard to catch, just see a faint signal

 

[Perry Babin]

Is the gate drive going all of the way back to ground squarely (very nearly perfectly vertical)?

 

[cajones65]

Can't tell Perry, pulsing to fast. I'm trying again.