gu37fhd1080 no backlight

[wreksta]

hi al just got this set in and ive checked the power board megmeet mlt1668tl

I have only 1.2 v on the 24v connection for the inverter (I don't have any vaults with inverter disconnected at the 24v point)


I do however have all the 5v at these points 5vsb 5v stb 5v

but no 12v

ive measure the big cap on the board and get 344v across it

any ideas

[tom66]

Re: gu37fhd1080 no backlight

The results should prompt you to check PSON signal...
and provide pictures.

[wreksta]

Re: gu37fhd1080 no backlight

not my pics but you get the idea
where is the pson on the this

[tom66]

Re: gu37fhd1080 no backlight

What are the labels on connector between main board and power board?

[wreksta]

Re: gu37fhd1080 no backlight

hi tom the connector between the power and the main has nothing on the main board just obn the psu which is marked

12v
12v
gnd
gnd
5v
5vsb
stb
5v
gnd

[tom66]

Re: gu37fhd1080 no backlight

STB is PS ON on this unit, check that voltage in standby and after pressing power button.

[wreksta]

Re: gu37fhd1080 no backlight

hi tom that voltage is 3.9 both in standby and powered up

[tom66]

Re: gu37fhd1080 no backlight

seems to indicate a power board fault but just to rule it out you could use a 100~470 ohm resistor between 5VSTB and STB with main board out, the voltages should come out. Also try isolating inverter in case it has a short on it.

[wreksta]

Re: gu37fhd1080 no backlight

hi tom nah nothing happened mate the voltages just are not coming

should that main cap be 344v on or standby

any other ideas for me

[tom66]

Re: gu37fhd1080 no backlight

344V standby is fine, about 390V to 410V when running.
It's a power board fault, not sure what else you want me to suggest? Tested the obvious like start-up capacitors, shorted diodes, optocouplers, etc.? All the testing procedures for those are available on the wider internet.

[Kilroys]

Re: gu37fhd1080 no backlight

I can read MLT668TL on the white label on the psu and this service manual is among the other manuals.