Ssi_400_14a01

[ReeceyBurger123]

Hello, requesting for some help on this flaming inverter originally came to me with failed Mosfets that drive the transformers after replacing them the inverter worked for about 14 hours while testing the all of a sudden my new Mosfets blew up which are BA6366 type originals are BA9T56 nothing checks shorted but my new Mosfets what could be blowing them out hate these boards. Any help is much appreciated thank you.

[ReeceyBurger123]

Re: Ssi_400_14a01

Boost

[ReeceyBurger123]

Re: Ssi_400_14a01

Boost

[tom66]

Re: Ssi_400_14a01

I cannot find a datasheet for either of those MOSFETs.

[ReeceyBurger123]

Re: Ssi_400_14a01

Hmm will get all the other numbers now buddy.

[ReeceyBurger123]

Re: Ssi_400_14a01

Right heres what I got:
Original Mosfets that come with Inv all numbers:
4614
BA9t56

[ReeceyBurger123]

Re: Ssi_400_14a01

The new mosfets that I installed:
4614
BA636G

[ReeceyBurger123]

Re: Ssi_400_14a01

Now the ones I installed the middle ones that were originally blown I replaced all 6 that drive the top two most transformers but the 3 middle ones have failed again, my finger is next to in the photo are the ones that failed again.

[tom66]

Re: Ssi_400_14a01

They are AO4614
https://cdn.badcaps-static.com/pdfs/...df367ff0cc.pdf
I would check the drive waveforms using a scope if you have one.
I would also check if there is a thermal pad - this must be soldered.
Could be a bad transformer or bad bulb.

[CapLeaker]

Re: Ssi_400_14a01

did you check your transformers yet? They should be within 3% of each other.

[ReeceyBurger123]

Re: Ssi_400_14a01

Thanks chaps will check all that tomorrow these dont have thermal pads on the bottom so thats out the window I also read up about thw Zero ohm jumpers for these having bad solder joints will have to investigate. Cheers.

[ReeceyBurger123]

Re: Ssi_400_14a01

Its strange as it worked for a while then blew again, looks like more digging to do.

[budm]

Re: Ssi_400_14a01

Any sign of the board under the transformers have turning brown due to heat?

[ReeceyBurger123]

Re: Ssi_400_14a01

Any sign of the board under the transformers have turning brown due to heat?

Not under the transformers but under the 3 Mosfets that have failed again, there is obvious discoloration and browning on the pcb.

[ReeceyBurger123]

Re: Ssi_400_14a01

There are 4 transformers in total along the vertical height of the board, 3 are big ones and 1 is small. The bottom two big transformers have 4 Mosfets each driving them while the top big transformer and small transformer only has 3 each driving them. There are two independent driver circuits on this Pcb on for the lower transformers and one for the upper set of transformers, so could it be possible that the driver circuit runs the 3 Mosfets that drive the large transformer at the top at a faster rate than the others to maintain the same brightness ? Could this circuit have been damaged by the failed Mosfets and is over driving them ?

[ReeceyBurger123]

Re: Ssi_400_14a01

They are AO4614
https://cdn.badcaps-static.com/pdfs/...df367ff0cc.pdf
I would check the drive waveforms using a scope if you have one.
I would also check if there is a thermal pad - this must be soldered.
Could be a bad transformer or bad bulb.

Thanks for the Pdf as well

[tom66]

Re: Ssi_400_14a01

I doubt it is 3 transistors driving one transformer it will be a half h-bridge or full h-bridge which requires an even number of switches to work.

[ReeceyBurger123]

Re: Ssi_400_14a01

Hmm maybe you are right and its 4 for the big transformer then 2 for the small one.

[ReeceyBurger123]

Re: Ssi_400_14a01

I have some new parts on order and going to start checking things later on will let you know if I find anything.

[CapLeaker]

Re: Ssi_400_14a01

check that transformer that has those 3 failed FET's and maybe swap the CCFL's around. Maybe the fault shifts?