Hello,
Today I am working on an inverter board and trying to determine the problem.
I have tested all the MOSFETS and found them all to be ok.

In fact, the only problem I can find with the board appears to be diode related.
The problem is that it will not power up and presents a short across the fuse terminals.

There are a number of 1N4148 diodes that give odd readings. In one direction of the diode test with my VOM they read approx half a volt.
in the opposite direction nearly 1.5 volts. Since it shows voltage in both directions I assume they are bad.

I removed one of the diodes as shown below.

Is my assumption correct?

Thank you

 

You can only measure the diodes when they are removed from the circuit. How did that 1N4148 test after you removed it?
A 1N4148 is a small diode, and would blow if any amount of power was applied to a bad diode of that type. Another possible cause is a shorted MOV (surge protector). Something similar to that blue thing next to D13

 

Well, I ended up making a new Circuit board for this mostly as a learning experience.
I unsoldered and re soldered components onto the original board so many times it had too many pulled pads and tracks for my liking.
The Inverter now works perfectly. The ONLY problem was that I accidentally installed the P50N06 Mofets backwards.
Anyway....I have brand new replacement PCB's for this inverter if anyone needs. PM me.





I'm probably the only source on planet Earth for a replacement circuit board for this inverter


That said.....
And I'm probably the only one on planet Earth who would need / want one.
It's a more than 10 year old design and only Modified Sine Wave (and only 300watts)
But sometimes in my vehicle 300watts is all I need...not to mention a fun learning experience.