LG 42PG20D-AA main processor problem

[maxvalutech]

Kerbside pickup but very good condition inside and out. At first check picture frozen and remote use intermittent plus at times loud buzzing. Took PSU out and resoldered coils etc but no change. Ran the test patterns and all OK there. So then took out mainboard and ran heat gun over it particularly around sides of main processor. Now the picture runs OK but with most remote or button changes the sound will stop with last word repeated about 8 times the set then auto turns off and starts again all well though it may do that again a few more times - after that remote signals have no effect other than to turn set off which takes 10 or so seconds before it does go off. So I think the main processor is still not working right. Got into service menu (with menu/menu) but no option to reset found. Did reset on ordinary menu. The set has been going now for 30 mins with DVD playing but won't respond to remote at this time. Main is EAX41533504(0). Set is from 2008/9. Might try the oven.

[maxvalutech]

Re: LG 42PG20D-AA main processor problem

Well at last some success with two sets fixed before lunch!! A diode I've been waiting on for about 7 weeks finally got here and fixed power board in one set a plus 15mins at 180c has cured this LG of its stutters. Now I'm not a fan of the baking method but in this case it worked. I must say too that the pic looks great on standard settings - the owner, whoever it was, certainly looked after it well.

[neilc6]

Re: LG 42PG20D-AA main processor problem

I've baked a HP laptop main board and a ps3 board. Both worked for around a month before problems re-occuring.

[maxvalutech]

Re: LG 42PG20D-AA main processor problem

Yes time will tell.

[Andrew F. Ali]

Re: LG 42PG20D-AA main processor problem

I personally do not believe in the 'oven baking' method as I have observed from previous posts over the years to be unreliable and temporary. However, I have tried the Hot-air Station approach and that repair seems to be longer lasting if not permanent. With the Hot-air Station I am able to control where the heat is focused and do not run the risk over heating other components thereby weakening or shortening their life. Not to mention the risk of melting plastic housings. bodies and supports if any.

[diif]

Re: LG 42PG20D-AA main processor problem

Baking in an oven is almost as bad as using a paint stripping heat gun. However if that's all you have and it's either that or buying another board there is nothing really to lose.

What do you think you are fixing with the temperature at 180c ? It's not hot enough to reflow lead free solder.

[Andrew F. Ali]

Re: LG 42PG20D-AA main processor problem

+1.
You need for a minimum 350C for the solder to melt. I have found that this is a common problem wit LG TVs where BGA IC need a reflow to solve most Main Bd. issues. I use 350C at Fan speed at 4 for 10mins, allow to cool on its own and retry Main Bd. on TV. Worked for me about 5 times already and 2 of them were like a little over a year ago and still going strong.

[maxvalutech]

Re: LG 42PG20D-AA main processor problem

Our oven is domestic fan forced (I didn't use fan) and I used foil to wrap board in. The time was probably closer to 20mins with board placed lowdown near element then left in oven to cool door open and cooling fan running. Attachment may be of interest.