output mosfet fails if + and - supply shorts

[nonprof]

Hello!

I have a question, why the output mosfet IRF640N fails and amp goes to protect, if accidentally shorts the +- of the amp? The second time I short the +/- supply the output mosfets fails again, do it at 3rd time and another mosfet fails.

These are newly installed fets, Did I used a counterfeit mosfet? or the low voltage protection is not functional?

This is amp is china made amp, 850rms mono. It uses 2 NOR Gates.

regards,
Armand

 

[Perry Babin]

Are you shorting the speaker +/- or the B+ and ground?

Why are you shorting them?

 

[nonprof]

I shorting the +/- power supply not the speaker terminals. testing them if worth for dispatch.

 

[Perry Babin]

testing them if worth for dispatch.

What do you mean?

 

[nonprof]

What do you mean?

testing the durability of the amp.

 

[Perry Babin]

Are you shorting the B+ terminal to the ground terminal with power applied?

 

[nonprof]

Are you shorting the B+ terminal to the ground terminal with power applied?

yes Perry.

 

[Perry Babin]

I don't understand why you would do that (I guess it's not important for me to understand) but that shouldn't cause the output transistors to fail.

 

[nonprof]

I don't understand why you would do that (I guess it's not important for me to understand) but that shouldn't cause the output transistors to fail.

Ok.thanks Perry. Maybe I should find a original mosfets.