LG 50PS3000 garbage find

[tom66]

My best garbage find yet.

LG 50PS3000 with intact screen. (50" 1080p 2009 plasma panel.) Back cover was present but ALL screws missing so guessing someone had a fiddle. All boards in the set though and all cables hooked up. Minor damage to main board speaker cable but looks repairable.

Found PSU fuse missing but couldn't find any shorts on the PSU so presume this was a diagnosis step but forgotten about by someone. Think set might have had the common pink tint issue as found two shorted FETs on Z-sustain near Vzbias generate & bias ckt. Since fuse on Z-sustain was OK & Vzbias regulator FET was OK, I suspect the shorts could have made PSU cycle on and off (the regulator FET would not have any current limiting.)

Will replace Q13,Q14 & Q15, plus PSU fuse and with any luck it should work. There is always the chance of bad panel due to vertical line on these but usually it is minor and I'm not complaining for a freebie.

[Shinju]

Re: LG 50PS3000 garbage find

Free is good!

[jose6326]

Re: LG 50PS3000 garbage find

free is always good

[Shinju]

Re: LG 50PS3000 garbage find

My latest free ended up having a cracked screen, BUT good parts!

Samsung LNT4665FX/XXA

[tom66]

Re: LG 50PS3000 garbage find

Lamp tester on PSU appears to indicate the PSU is OK. Need to get a new fuse to be certain but it looks good so far.

[ecking767]

Re: LG 50PS3000 garbage find

2009 model nice find !! I haven't found any TVs lately by my job dumpster, but someone brought a new Samsung 55" LED HDTV and they threw out the box leaving the stand & base with the mounting screws inside the box. easy sale!!

good luck with the repair !!

[tom66]

Re: LG 50PS3000 garbage find

Got some fuses. Fired it up and I get a red picture, just as expected. (Z-sustain unplugged.) Great! I just need to repair the Z-sustain and it'll be perfect. No stuck lines on panel.

[tom66]

Re: LG 50PS3000 garbage find

FETs in and picture looks great!

However the Vzb measures 135V (should be 97V) and will not adjust. Think I may have to replace other FET too... Result is a good picture but dark areas have sparklies - will have to see why the Vzb is too high.

Still, panel looks good even with mild sparklies.

[johnboy1313]

Re: LG 50PS3000 garbage find

Awesome

[9302z28ss]

Re: LG 50PS3000 garbage find

youre pretty good at this tom, maybe you can help me figure out my issue with my panisonic tc-p42s30 power LED comes on i hear two clicks it shuts off then 15 sec one more click, no idea what to try here sorry to hijack

[tom66]

Re: LG 50PS3000 garbage find

Please keep questions in your thread, tw2005 is helping you right now, no point in me joining in.

Pulled the regulation transistor... this is a little odd... it tests OK on my transistor tester, but from drain to source (fwd biased) on my meter I get about 5.5kohm which is a little unusual. Seems like it might be breaking down under load. I will replace it, cheap part. FQFP51N25.

[senndogg]

Re: LG 50PS3000 garbage find

Good luck with that! seems that the entire zsus is £49 on ebay. anyway which are easier to troubleshoot and repair, the boards with individual transistors or the ones with hybrids?

[tom66]

Re: LG 50PS3000 garbage find

By a factor of about 10x the ones with individual transistors are easier (like this one), and they are also more repairable!

[tom66]

Re: LG 50PS3000 garbage find

Fixed! It was that FET. Even if it tests good in almost every way, it can be failed!

Clues for failure: Drain of FET was at 195V (Vs) and its purpose is to linear regulate the Vzbias supply, about 100V. The Vzbias actually measured 130V and as the set ran and warmed up, it creeped up to 150V, causing a very maldischarged image with high image retention and sparklies - bright images OK though. The source of the FET measured 130V-150V as expected (linear regulator) wrt to GND, but the gate ALSO measured the same, which indicates the control circuit was pulling gate LOW but FET was not acknowledging this "command".

Components replaced:
Q13,Q14,Q15
ZD902
R407,R408

Total cost = £13, TV was free.

Amazing what people will get rid of.

[Shinju]

Re: LG 50PS3000 garbage find

Awesome!

Just wish all of them can be this easy

[tom66]

Re: LG 50PS3000 garbage find

Don't like the LCD-like black level on this panel :/

Tweaked it:
-Vy to -170V (from -180V)
Vzbias to 80V (from 97V)
Set-UP turned down so ramp does not reach full Vs, verified using scope
Set-DN adjusted til maldischarge, then added a little extra margin
Vs/Va/Vsc not touched

It looks PZ80-like now - not fantastic but far, far better!

[thuss]

Re: LG 50PS3000 garbage find

Hi Tom66

Ive got the same set but the fuse is blown on the z sus is there a repair kit for that? I cant find one

(or if anybody could hep)
thanks in advance

[tom66]

Re: LG 50PS3000 garbage find

There are repair kits on eBay about £25 which is a good price considering all the parts involved, in most cases it's just those three transistors and some resistors that fail.

[mwalsh]

Re: LG 50PS3000 garbage find

How do you go about rain soaked bin finds in the UK? We don't get much rain in this part of the Americas (and it's getting to be less each year!), but I do tend to avoid dumpster diving in the days following a rain storm, because I don't want to bother tearing a set apart and drying it all out first before I can even try to fire it up and see what might be wrong.

[drgears]

Re: LG 50PS3000 garbage find

If you want more sets to play with,,,,,I have an ad running on craig's list that nets me a set or two ,,,getting tougher though ,,,more people getting into trying to repair or harvest parts for cash,,but will help you get more "stuff" to play with...Can you ever have enough broken TV's ??????