Rockford Fosgate T3002 Protect mode

[jtaborsky]

Hey everyone, this is my first post.

I recently acquired a known-bad Rockford Fosgate T3002. When I apply power to it, it immediately goes into protect mode. The protect light turns on, but the power light does not even flash. The thermal light also sometimes slowly illuminates and then slowly turns off. I checked all the FET's with an ohmmeter, and there was a short on one of the output FET's between legs 2 and 3. I removed that FET from the board, as well as the other FET that was parallel with it, but I am having the same problem; the amp still goes into protect mode.

What would be a logical next step to check? All the power supply FET's have 13.8 volts between their middle leg and ground.

I have an associate's degree in electronics/telecommunications, so I am somewhat able to understand terminology, but it has been many years since I studied. I do not have access to a scope.

Any help is greatly appreciated!

Thanks.
- Joe

 

[Cortez]

What would be a logical next step...?

To get the schematic, and check all the critical nodes. Without the schematic it wont be easy.

 

[jtaborsky]

Does anyone have the schematic for a Rockford Fosgate T3002?

Should the amp power up normally with the faulty output mosfet and its parallel mosfet removed?

Sent from my SCH-I435 using Tapatalk

 

[jtaborsky]

Reviving my own thread from 2016. I gave up on this project for a while, but decided to do some learning!


Where can I get a schematic? I now own an oscilloscope. The transistor that is shorted is Q118.


Does protect mode (with faulty component removed) suggest further issues?


Looking to learn, and any advice helps!


- Joe

 

[rodner]

Check for DC offset on the speaker terminals. I believe it trips protection over 100mv. Some amps that I've come across won't power up with components removed. So, you may have to replace those bad fets, first.

 

[jtaborsky]

DC offset on left channel is ~13mv and right channel is ~15mv, so I think I'm good there. Should all tests be done with exactly 12v power? Are there any test points to determine why the amp is in protect? I will replace my shorted FET's this weekend. Is there a test I can do to determine which FET's need to be replaced together?


Thanks again for the help.


- Joe