Ssi_400_14a01

[ReeceyBurger123]

Re: Ssi_400_14a01

Yeah will also going to check the drive voltage for them just to be sure that they arnt being push harder than the others. I dont think its a failed lamp or transformer because when it worked image was fine and if that was the case wouldn't the protection circuit shut it down these are sensitive as had one before with a failed lamp connector and it would shutdown instantly? Will check when I get back thanks guys

[tom66]

Re: Ssi_400_14a01

The protection circuits only detect open lamps (over voltage) and shorted loads - and usually, the shorted load detection only works by under voltage or power supply cut out.
So intermittent faults or bad transformers aren't always detected.

[ReeceyBurger123]

Re: Ssi_400_14a01

Yeah the shorted mosfets dont blow the fuse but kill the 24v rail and Psu shuts down. Going to start diagnosing now

[ReeceyBurger123]

Re: Ssi_400_14a01

Here what I found, also it is 3 Mosfets for the transformers at the top btw there isnt any chain between them all so dont know how they do that here is the resistance readings for the transformers.

Bottom 2 transformers:
Secondary resistance readings 1490 Ohms same on both transformers.

Top large transformer with failed mosfets:
Secondary resistance 1512 ohms and 1516 ohms on both secondary windings, failed ?

Top small transformer:
Secondary resistance 1015 Ohms per winding.

[ReeceyBurger123]

Re: Ssi_400_14a01

The controller Ic is a SEM2107 0929 chip, this is included in some repair kits for this INV.

[ReeceyBurger123]

Re: Ssi_400_14a01

Going to take the transformer off and swap it.

[ReeceyBurger123]

Re: Ssi_400_14a01

Here is a youtube video of what I have done so far:
https://m.youtube.com/watch?v=C6zbTDLx3ug

[ReeceyBurger123]

Re: Ssi_400_14a01

The transformer is not at fault but I swapped it anyway, nothing is shorted but however do you think its worth checking the drive voltage for the fets and swapping them out again just to be sure its not the driver circuit ?

[stj]

Re: Ssi_400_14a01

did you check the ceramic caps between the transformers and tubes?

[ReeceyBurger123]

Re: Ssi_400_14a01

The ones on the inverter Pcb buddy ?

[stj]

Re: Ssi_400_14a01

obviously.

they stop the tube drawing too much current.

[ReeceyBurger123]

Re: Ssi_400_14a01

Yeah they are fine

[ReeceyBurger123]

Re: Ssi_400_14a01

This one is a pain going to risk it tomorrow and put my new mosfets in and start checking things.

[stj]

Re: Ssi_400_14a01

check everything related to the controller ic.

got a datasheet?

[retiredcaps]

Re: Ssi_400_14a01

check everything related to the controller ic.

got a datasheet?

https://www.badcaps.net/forum/showthread.php?t=36735

[stj]

Re: Ssi_400_14a01

btw, i dont suppose you have a logic analyser?
just incase the controller is doing something it shouldnt!

[ReeceyBurger123]

Re: Ssi_400_14a01

Thats what I suspect the logik Ic is included in some of the Us repair kits now im really starting to think that it could be messing up somewhere. I dont have an analyser though so will have to start checking things tomorrow cheers Stj.

[tom66]

Re: Ssi_400_14a01

btw, i dont suppose you have a logic analyser?
just incase the controller is doing something it shouldnt!

Scope would be more useful - logic analyser won't handle the level-shifted gate outputs, or usually anything more than around 5V. Gate drive will go above 24V on this if it has high side N-channel FETs.

[stj]

Re: Ssi_400_14a01

true, but some resistors and zeners would probably fix that, as long as it wasnt running faster than the LA.

i have a new one on the way that can sample at 24Mhz - i couldnt resist for £5!!!
http://www.ebay.co.uk/itm/141694353386

[ReeceyBurger123]

Re: Ssi_400_14a01

Thanks everyone