Im having problem with chinese Do Power 2500W inverter.
At least couple of 8 HY4004 transistors have blown and cracked.
I have 2 optional mosfets what to use, any ideas which ones should i use to replace those original ones, IRF2805 or IRF3703?

 

Check all the electrolytic capacitors too as their failure often starts the problems. Replace with the same sort of low ESR types.
The IRF2805 does not have the current capability of the HY4004, and the IRF3703 does not have the volts.
Can you get the originals?
Try to find out what caused the FETs to fail, otherwise the new ones will mos likely do the same.

 

Hi Dendad,

Unfortunatelu i have no possibility to get those same original ones.
I checked all electrolyt caps, those look ok, no pumbs, leaks or cracs, still decided to order largest one just in case as it look even slightly round shaped if compared the others. And as this is at summer cottage all eguipments, spares and tools are more than difficult to get now and all advices are more than welcome.

 

Can you remove the caps and measure their capacitance?
Make sure you put them back the correct way.

I would not replace the FETs with a lower voltage version. My vote for the popping of them would be voltage spikes. And at the power level in question, going lower in current may be risky too.
All the FETs would best be the same I think, to help current sharing.
Maybe...
https://au.mouser.com/ProductDetail...DBzk1/WizSW%2bwlCH/hMnfHjD3Efj2PhrFxZjTkdpQ==
https://au.mouser.com/ProductDetail...hyDBzk1/WizrSbRfT/m2Uejk6hoiRCobhv3qWdJXUCQ==

 

Manufacturer send me suggestion to use if possible. IRF4310 or IRF4110.
Also got tech drawings, but honestly doesnt help that much with current available tools.