LG 37LC55 solarised pic

[finntricky]

new project, lol
solarised picture after being on for a few mins, with lines and jumping picture.
gama volts all over the place.
changed AS15F chip, now got good readings from 15.3 down to 0.3 except 2 test points show the same volts at 4.3 volts.
tv still acts the same as it did before changeing the AS15F chip ?
what do you guys think ?

[tom66]

Re: LG 37LC55 solarised pic

You may have got a dodgy gamma IC or chip not soldered right... could also be a main board fault.

[finntricky]

Re: LG 37LC55 solarised pic

You may have got a dodgy gamma IC or chip not soldered right... could also be a main board fault.

maybe tom, but the time it took me to get it right was long enough, don't fancy
going though that again, it was my first time at one, lol, was on and of 3 times,
untill i got my USB microscope, man, talk about shorts on the pins, it looked fantastic with a maggy glass.
but i have got another chip, just in case i messed this one up,
wonder if overheating the chip with hot air would damage the chip.?
as it has had a few warmings.

[tom66]

Re: LG 37LC55 solarised pic

The first three attempts for me did not work and I have done chips like those before. They are unusually sensitive, I don't think the lead-frame material is very good compared to other QFP devices.

[splitcrete]

Re: LG 37LC55 solarised pic

Those as15 chips are sensitive, temps. over 500-F or 258-C will cook them. I only use a small amount of solder paste with my smallest drag solder tip. Paste melts at 430-F or 218-C . Takes practice. The chips from China I found have a 2 in 10 D.O.A rating .That is from my experience using them.It is also useful to use an IR Thermometer to monitor the chips heat. Hope this helps.

[budm]

Re: LG 37LC55 solarised pic

2 in 5 for me for the chips from China.

[Alastair E]

Re: LG 37LC55 solarised pic

Ive not had any issues with any AS-15 Ive done. I dont use hot air, just a temp controlled iron lots of flux and standard lead/tin alloy solder...

Oh--And I take my time!

[finntricky]

Re: LG 37LC55 solarised pic

chip must be 99% on right, may be there is still a bridge somewhere, as 2 test pads show same volts, and there next to each other, 16 and 17

[splitcrete]

Re: LG 37LC55 solarised pic

No one likes a showoff Alastair...LOL

[finntricky]

Re: LG 37LC55 solarised pic

ok, now put new AS15 chip on t-con, and voltages are much better, decreses as they should do,
still same prob with picture, after being on for a few mins, so gonna put it down to main board, can;t find one the same to replace it,
looks like another tv to sell as is.