Back light problem

[snipersquad100]

HI I've got an ALBA LCD32880HDF in with a back light going off after 30 secs or so. voltages are a bit of a problem as their not marked on the pcb. When it starts up im getting a 24v, 12v, 5.3v, 3.3volts when the back light goes off the 24v drops to 18v. So im not sure if I have a PSU or an inverter problem or something else.
thanks

[snipersquad100]

Re: Back light problem

anyone

[budm]

Re: Back light problem

Good clear pictures of the back of the TV and the boards so we can see what we are dealing with?

[snipersquad100]

Re: Back light problem

here's some pics

[selldoor]

Re: Back light problem

Pictures are nor really clear enough - need to be able to read the component numbers on the boards. When it is on can you tell if any bulbs are out (one corner dimmer etc.)
We also need a pic of the inverter board and possibly the Tcon.

[budm]

Re: Back light problem

I need good clear pictures of that power supply/inverter board combo top and bottom side. That high voltage inverter transformer is not likely to be running from 24V power supply but more likely from the PFC Voltage booster circuit that supplies about 380~400VDC to drive that transformer through MOSFETs. I cannot tell until I get to see better pictures to figure out how this board works.

[snipersquad100]

Re: Back light problem

Sorry had to use flash as its dark. If you need better ones I'll have to take em in the morning. Thanks

[snipersquad100]

Re: Back light problem

[budm]

Re: Back light problem

Did you take the screen apart?
Pictures of the bottom side of the power supply board? I need to be able to see good clear pictures of the components on the bottom side of power supply board to see how the inverter transformer being driven.
This is going to be tough, there are so many pins on the power supply/inverter board connector that goes back to the main board.

[snipersquad100]

Re: Back light problem

yes screen is apart, give me have hour to do the underside of the pcb.
yes this is a tuff one, Ive never worked on a psu/inv combo b4. if I could be sure its the psu/inv and not the back light or something else id buy a new board.

[budm]

Re: Back light problem

I am not sure if the 17IPS10-2 SCH is close to your -03 or not, but it may help.
I download this from TOM66 website.

[tom66]

Re: Back light problem

This PSU uses 150V for backlight inverter. I would check what this does when fault occurs.

[snipersquad100]

Re: Back light problem

Hope you can piece it together.

[snipersquad100]

Re: Back light problem

where do I prob for the 150v?

[tom66]

Re: Back light problem

We don't need board layouts at the moment with, uh... "schematics" (if you could call Vestel's attempt one.) Check 150V. Across C164, I think.... (schematic completely unclear.)

[snipersquad100]

Re: Back light problem

Ok will do. Any more pics needed b4 I put it back together.

[tom66]

Re: Back light problem

Should be OK for now.

[snipersquad100]

Re: Back light problem

I cant see c164 to save my life, on that schematic its a 220uf/200v should stand out like a sor thumb.

[snipersquad100]

Re: Back light problem

this board is vestel 17IPS10-3 the schematic is 10-2.
wait just found c164 and its unpopulated cap.

[snipersquad100]

Re: Back light problem

is it worth getting the reading across the pads.