Logic 32LW782 intermitent fault

[westfield1]

 Logic 32LW782 32" Turn on sound but no picture, turn off, turn back on still the same, leave on 10 mins, turn off and back on now got sound and picture. any pointers would be welcome.
Paul.

[Turnip]

Hi Westfield1,

Don't have it listed - who made it  ? - Some piccies, maybe - Chris.

PS - Sounds like duff caps, warming up perhaps  -

[westfield1]

Hi Chris, i dont really know who made it but it has got a vestel 17pw20.1 psu board when i got it it was completely dead but now its got this  fault it happens about 1 in 20 turn on's i thought a bad cap but without an esr meter i will struggle to find it as all the caps look ok and read capacitence ok.

When it happens i get sound and thats it and it will stay like that until you turn it off.......Paul.

[Ohm Supplies]

paul.

Do you get a backlight or just sound only?

Is the 24v present from the psu when this happends?

regards
Andy

[westfield1]

Hi Andy, no backlight i have not check the 24 volt, when it happens i get only sound if you put a torch to the screen i cannot see a picture so i am asuming no backlight, no picture just sound....Paul.

[westfield1]

Update, now its doing something totally different when i turn it on from standby the stby light goes out the screen lights up then goes out straight away and nothing, i have to unplug it and plug it in to get the stanby light and just keeps doing the same.

[westfield1]

This one is driving me crazy   

Ok its randemly going from....

Standby light picture for a split second then shut down.

Next time at power up from stby i get sound picture no backlight.

next time all works ok.

I have tried another psu, is there something obvious i'm missing, is this pionting to the main (17MB12.1) ?

Paul.

[fix2003]

only tip i have

Vestal 17PW20 1 Power supplies intermittent not starting

Fault: Not starting, no backlight, switching to standby. Can be very
intermittent depending on temperature.
Cure: Replace R817, R818 and R819, all 620 K sm beside ic802 power factor
IC. One or all can drop in value.
The voltage across the mains smoother will be low about 330V instead of 380V
and the 24V supply will be low at 21v.

[westfield1]

 
Thats been really helpful, think that i have not helped myself by trying 2 different 17PW20.1's as i now feel that they both are slightly faulty by that i mean one of them switches on from standby then shuts down straight away and when i fit the other one the tv will turn on fine from standby and work as normal 19 times out of 20 but occasionally turns on but no backlight.........Paul