Lg50pb690v

[sparks2112]

Hi guys. Any help much appreciated. Got this TV a while back but never had time to look at it right. Done obvious stuff like caps all good.
Problem is when turn on screen flashes white/grey split second and goes off no pic. TV still on as can use remote to turn on and off. Would like to start over fresh with some help off anyone please. what to go through,try.test etc. Until we can find problem or parts I will need.
Like I say any help is much appreciated and can't thank you guys enough just for taking the time to help out.
Bare with me though as proper noob

[Hamie]

Re: Lg50pb690v

Got a Green light on control board?

[sparks2112]

Re: Lg50pb690v

Yes bud green for 1 sec goes out then quick flash. Then off for 2 secs repeat.

[Hamie]

Re: Lg50pb690v

OK you see the glue on at the bottom of the y-sustain. Usually stuck to the side of the transformer and a 2.2 ohm resistor.

The glue becomes conductive and causes havoc to this board.

Scrape as much of it as possible away.

This might not be your fault, but try this first and see if the picture comes back.

[sparks2112]

Re: Lg50pb690v

Yes seen a bit something on this forum about a capacitor under that glue c205 I think .cleared glue from that and tested cap seems OK. Going to clear all off now and get back to you soon thanks

[sparks2112]

Re: Lg50pb690v

No change still same

[Hamie]

Re: Lg50pb690v

OK so you'll need to check the voltages.
Annoying this TV tends not to show the correct voltages on the z-sus if the y-sustain is faulty.

For example (from memory) the VZB voltage should be 140v, but if the ysus is faulty it will sit around 70v

Also run test patterns on control board.

[sparks2112]

Re: Lg50pb690v

Vzb 140.3 i found a dead resistor r563 on ysus changed it .just noticed a small spark when booting up now. ysus a mosfet d442 going to check that out back soon

[sparks2112]

Re: Lg50pb690v

My bad lol. Not soldered resistor right. Resolded and now spark gone.va and vs and standby voltages correct.m_on & rl_on read 3.31v when tv turned on. All voltages right going to zsus and ysus. Not sure what I'm looking for to be honest. Need to more research on parts and testing. I'm more a cap or board changer

[sparks2112]

Re: Lg50pb690v

Well getting late work in morning. will look in tomorrow
Thanks for help so far

[Hamie]

Re: Lg50pb690v

So you need to check -vy and vsc voltage on the y-sustain.

[sparks2112]

Re: Lg50pb690v

Hi hamie really sorry on late reply. I work on marquees and can be away for days/weeks at a time.just got back will get back on this tomorrow and let you know. Sorry again sparks