They both have IRFP260N pass transistors; these appear to be genuine IR brand, but reclaimed parts. So the claims of "shorted transistor new out the box" I've read are not necessarily bogus; these tend to be the most common point of failure in any kind of equipment that uses them for obvious reasons. I recommend removing and testing the FET with your Cheap Chinese Component Tester and doing the recommended crowbar zener and maybe adding a fuse mod before actually applying power to this device.
mnem
The IRFP260N is not a great choice for this application. The package is only rated for 300 watts and 175C. It will get pretty warm.
It must be specific sales threads on aliexpress that list the IXYS mosfet. I bought from here and I don't see the mosfet listed in the comments or elsewhere. Oh well...don't really care I guess. I'll just use 2 TO-247 mosfets in parallel. That ought to get me plenty of current capability.
https://www.aliexpress.com/item/1005001565062996.html?spm=a2g0s.12269583.0.0.24527e8eBUrMDJI googled for the part number on it. This is what I found:
https://pdf1.alldatasheet.com/datasheet-pdf/view/126167/IXYS/VMO400-02F.htmlHowever going straight to the IXYS/Littlefuse web site did not find this device. Mouser didn't have it either. Maybe its a fake part or some Chinesium knock-off?
Regardless, it's just a big mosfet in there...
I noticed this too. The original mosfet was not what I would call "new looking". I did test it on a component tester and it seemed OK so I used it as is. The first capacity tester I got, the mosfet did NOT test OK. I sent it back! Those inexpensive Chinese made component testers are super handy! I've vetting thousands of used parts with them.
A fuse...that's a good idea! After you beef up the traces, better heat sinking, zener, larger shunts, etc...a fuse would be a good add-on too.
Before I killed the CPU output for the mosfet, I had just gone to 10 amps on a 3S LIPO pack or about 125 watts. The LCD never showed more than 10 amps so I was under the 180 watt limit. Maybe even with the zener in place, amp draw peaked way over this? Before I beefed up the traces, the drain trace had already melted through right at the leg. I also cooked the 2 tiny shunts. A fuse or reset-able breaker may have saved it from further damage after I removed the other weak spots.
I have 2 of the DIY boards coming. I tried to repair mine, but the driver circuitry is blown back inside the CPU. I think because semi's tend to blow to dead shorts that a way to protect the gate driver might be worth while. This is highly likely what killed mine. I think even a silicon diode would do the job. Put it between the mosfet gate and the driver circuit. This will limit the lower voltage some to over .7v, but I think that will be OK. The IXTH130N20T needs 5v to get to Vgsth so losing a little voltage won't hurt much by adding a diode inline with the gate.