Rockford Fosgate T1500-bd

[caraudioguy2100]

Should I get a clean square wave at the gates of all outputs ?

I’m getting a clean square wave at 2 outputs the rest of the outputs I get very distorted square waves

 

[Perry Babin]

The waveforms aren't as simple as other class D amps. Is the amp functioning normally?

 

[caraudioguy2100]

No the more input you give it the more distorted the audio becomes .

This amp is doing the same thing as another one I have here and can’t figure either one out .

 

[Perry Babin]

I'd suggest desoldering the center leg of the rectifiers and testing without rail voltage. Did you try that on the other one?

 

[caraudioguy2100]

With the center legs of both rectifiers lifted same result I get bad squarewaves on the gates of some of the outputs .

 

[Perry Babin]

You may need to close the feedback loop. I would need to know which driver board you have and I would need to see photos of the waveforms.

 

[caraudioguy2100]

Here are 4 different square waves I get on the outputs with the center legs of the rectifiers lifted .

Scope settings are 20us 5 volts/div

 

[Perry Babin]

Confirm that both adjacent red terminals are directly connected. If so, connect either to the other red terminal. That will close the feedback loop locally and will be easier to determine if everything in the drive circuit is OK.

 

[caraudioguy2100]

This is how they are connected on this board .

Does that make a difference ?

 

[Perry Babin]

Find the red terminal on the left that's NOT connected to the red terminal on the right and connect those two terminals with a small wire (small, not to stress the board connections).

 

[caraudioguy2100]

After closing the feedback loop the problem still exists on 4 of the outputs .

 

[Perry Babin]

Did the pulse width change at all after installing the jumper?

 

[caraudioguy2100]

Yes

 

[Perry Babin]

I can't make any suggestions without seeing the waveforms.

With no rail voltage, you can ground the scope to the gate leg of the FET being checked to get the best signal.

Be sure that the rail caps are discharged.

 

[caraudioguy2100]

Do you happen to know the value of the gain pot on this amp ?

It’s been replaced at some point and wondering if it’s the correct value

 

[Perry Babin]

5k. See attached for the original markings.

 

[caraudioguy2100]

Is this the same for the T1500BDCP ?

Not the older 1501BD but the new style where The pot is on a card

 

[Perry Babin]

The 6-terminal pot near the main board on the board with 2 pots is marked C20K.