Toshiba 32AV500U picture but no backlight

[DakotaKid]

Originally Posted by TechShui

Either that, or tape the black probe to the chassis (GND) of the TV, that way you can use one hand for the red probe, and your other hand free for the power switch.

I alligator clipped it to ground and took readings as I powered it on. Voltages never stabilize but I can see generally where they max out but unfortunately I get 0 bonus points because my DMM isn't a Fluke.

Originally Posted by TechShui

Umm, aren't the capacitor values marked on there?

Umm, no. There are probably a dozen or more SMD caps with no markings at all on them. I know their locations in the circuit, just not their values. The two 35v330uf are the only aluminum elect caps on the board and are also the only two with values marked on them or the schematic.

[TechShui]

I went ahead and tried it or myself.

I replaced the blown FETs, and the inverter controller IC.

My results are almost identical, with brief flash of the backlight, but then another 6-7 seconds later the backlight flashes again.

I straightened out the sync ribbon cable which seemed a little loose, but just made it go crazy, flickering on an off rapidly, and I think I might've burnt the IC again, because it now has image, but no backlight. Back to square one.

I see the pair of inverters for $45 on eBay
Considering the hours of time you will save, that's well worth it.

For the record, desoldering / resoldering the IC was not easy, and I damaged at least one trace removing the old one.

It's a 32-pin IC, with traces the thickness of a hair, I used a hot-air SMD reflow gun. And still I think a couple of the pins were not making good enough contact with the pads.
Dakota, if you're not ready to give up, check your soldering work, check the pads if they're cracked, and make sure they're not bridged.

I wouldn't worry about the caps or the transformers, you're over-analyzing. Just just focus on what countless people have identified as the problem: The FETs and the IC.

[kevinm34232]

Same problem for me, 2 shorted mosfets on slave board. Replaced the mosfets and inverter IC. All is working now. Using Chip Quik really helps.

At first when I hooked it back up I still was not getting backlight. I noticed Inv pin was now getting 5v but the 24v was dropping off. I left and came home a couple hours later to work on it and the backlight just came on.

Oh also after replacing Mosfets noticed fuse on same board was blown. Did not have a 5a 72v, so I used a 3a 63v fuse from a bad board, do you think that will be ok??

[kevinm34232]

Well backlight stayed on for an hour on so then went out again.. Fuse is still good.

Before I just replace the board, can this be caused by the lower value fuse even though it is not blown??