massive audio p1500.1 in protect mode

[Nutcase21]

Have one on the bench, my 1st massive and it's running in protect mode. all ps fets, rectifiers and outputs are fine. I replaced 4 caps next to the output filter coil due to leaking but otherwise I'm stuck. any ideas? Thanks!

 

[Nutcase21]

outputs are out of the circuit and it turns on and produces rail voltage. checked the gate pad for drive signal and I get rail voltage on 1 set of outputs. I'm going to test the drivers on that side and see what I find out.

 

[Nutcase21]

I found a single bad npn driver and replaced it but I still have rail voltage on the speaker outputs with a single output in each bank. I'm not getting the drive signal I'm expecting which lead me to the driver board where I have proper voltages but no low side drive signal. where to next? TIA

 

[Perry Babin]

Do you have a scope (assuming yes)?

If so, pull the rectifiers AFTER discharging the rail caps. Clean all pads to confirm that you have no solder bridges.

After you do that, you can connect the scope ground to the 3rd pad for the outputs and the scope probe to pad 1 for the outputs for both the high and low output groups. That will allow you to check the drive signals definitively.

 

[Nutcase21]

I found a damaged resistor on the driver card that must have come from when I pulled the top off and removed the potting. Can you give me a value for the missing resistor in the pic so I can replace it before I test for drive signal?

 

[Perry Babin]

10k?

I don't have a good photo of it.

 

[Nutcase21]

thanks what I thought too. I'm going to try it and see what I get. if not then i'll try a 1k.

 

[Nutcase21]

removed the rectifiers, installed a 1k resistor on the card (didn't have a 10k) and get nothing on the 1st pad for signal. I get 12vdc on the one bank and nothing on the other.