Taramps HD 5000 output mosfet heating up

[barber02]

I have a Taramps HD 5000 that has one of the output mosfets heating up a little more than the other three. There are a total of four output mosfets (IRFP90N20D).

It has two independent output inductors and they are using IR2010s driver ICs to drive the mosfets. Both sides are identical so I was camparing one side to the other and I found some differences in the voltages on the mosfet heating up versus the one in the same position that is not heating up.

The one that is heating up I have voltages as follows:
Gate 81.5
Drain 153.1
Source 81.8

The one that is not heating up I get the following:
Gate 75.0
Drain 153.2
Source 75.0

Across the speaker terminals I gat a voltage of -1.748

From positive speaker terminal to ground I get 75 volts
From negative speaker terminal to ground I get 76.9 volts

I was wondering what might cause this one mosfet heat up and have different voltages.

In the picture I have attached the mosfet that is warming up is located in the bottom left of the picture.

 

[Perry Babin]

The voltages don't match. The source of the high-side FET connects to the output. The source voltage has to match the output voltage.

Was this with the amp connected to a load?

Have you tried to swap the FETs to see if the problem followed the FET or with the location?

 

[barber02]

No. It was not connected to a load when I took the measurements.

I’ll try swapping the FETs when I get back home.

Thanks for the assistance Perry.