Alba lcd32880hdf

[sordids999]

hi guys

my latest project seems to be stuck with the standby flashing all voltages seem good until after about 10 secs when they drop to virtually zero unless i disable the main board from the psu then the voltages are fine

main board blown ? or could it be the screen even the backlight does not light up

thanks

[tom66]

Re: Alba lcd32880hdf

When you say "disable the main board" what do you mean? You can wire on the BL ON/OFF to check backlight.

[budm]

Re: Alba lcd32880hdf

Good clear pictures of the boards?

[sordids999]

Re: Alba lcd32880hdf

When you say "disable the main board" what do you mean? You can wire on the BL ON/OFF to check backlight.

sorry tom i mean this main cable going to the main board the psu makes a buzzing noise when i first test the voltages but this stops buzzing and the voltages drop pretty fast i have since got another psu but its still the same

[sordids999]

Re: Alba lcd32880hdf

Good clear pictures of the boards?

here you go

[tom66]

Re: Alba lcd32880hdf

These boards are a bit of a bugger because pins # on connector aren't labelled, schematic is here. By tracing grounds you can figure out orientation.
http://www.tgohome.com/ServiceManual...&Search=Submit

You'll want to check if the 5V standby is always present or not.
If it is, check the PS ON/OFF signal: STBY_ON/OFF.
If that drops out after it tries to turn on, it could be main board at fault.

[sordids999]

Re: Alba lcd32880hdf

pin 8 BL_ON/OFF starts at 5v then drops to nothing
pin 6 STBY_ON/OFF starts at 5v then drops to nothing

[tom66]

Re: Alba lcd32880hdf

Do you have steady 5V STBY, pin 14? What about 3.3VSTBY on pin 15, 16?

[sordids999]

Re: Alba lcd32880hdf

Pin 14 5v does not drop
Pin 15 4.9 to 5v does not drop
Pin 16 nothing

[tom66]

Re: Alba lcd32880hdf

Looks like your main board is bad. To confirm everything else is OK you can run a wire between STBY 5V to STBY ON/OFF and BL ON/OFF with connector removed from main board end. Backlight should come on, all voltages should be steady.

[sordids999]

Re: Alba lcd32880hdf

run a wire from pin 6-8-14 and no backlight coming on

[tom66]

Re: Alba lcd32880hdf

Just to make sure check you have 24V at inverter and >3V on blue or yellow wires going to inverter.

[sordids999]

Re: Alba lcd32880hdf

yes 24v at invertor but the blue wire going to the invertor has no voltage

[sordids999]

Re: Alba lcd32880hdf

the orange wire next to the blue has 2.5v

[tom66]

Re: Alba lcd32880hdf

Is the orange the last wire in sequence or ...? Last wire should be BL ON/OFF. Tap screen lightly, do you see a white spot?

Perhaps DIM need to be connected too, so try connection between BL_ON/OFF and B_DIM (#8 and #10.)

[sordids999]

Re: Alba lcd32880hdf

blue is the last on in sequence
and do you mean connect all together 6-8-14-10 ?
and no white spot showing when i tap the screen tom

[tom66]

Re: Alba lcd32880hdf

Yeah, when you get it correct there should be >2V on the last blue wire.

[sordids999]

Re: Alba lcd32880hdf

ok 5v on the last blue wire now

[tom66]

Re: Alba lcd32880hdf

Any backlight? Must also have 24V.

[sordids999]

Re: Alba lcd32880hdf

nope no backlight tom 5v showing on the blue end cable but 24v not showing on the invertor cables