PANASONIC TH-L19X10AK LCD - will not start.

[tw2005]

PANASONIC TH-L19X10AK LCD - will not start.

just finished playing with this one.
Symptoms were, green flashing LED, endless cycling, brief flash of backlight, audible click through audio, no fault code flashed.

Headed straight for the backlighting and disconnected P6,P7 to backlight.

TV cycled on for 2-3 secs then quit with SOS1, backlight error.

Connected antenna and heard channel on next startup, shone light into LCD panel and image could be seen.

Checked topside for shorts, nothing.

Then on underside Q7801 TPC8119(TOSHIBA FET P Channel MOS Type U-MOSV) - dead short
Q7802 TPC8037 (TOSHIBA FET N Channel MOS Type U-MOSV) - checked ok

Removed both with same result. No shorts on pad locations

Scavanged a SSG4407P from a dead laptop board for Q7801 and the TV is up and running again.

Have ordered TPC8118 from RS and will replace with that but it seems fine as it is.

Power board is TNP4G457 Rev: AD Same board as in TH-L19X10MK

3728Hrs on-time, 2758 power cycles

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

sadly it died today. Both FETS burnt particulaly the N channel which made a nice carbon mess.
Subbed both with the replacements I got and are of equal volatage and higher current rating.

lasted only half a minute or so and some nice aromas. you could see it was struggling to fired up and illuminate. Some fluctuations in brightness and then both burnt again.

I'm at sea with these, with the fets removed I can't measure any shorts or low resistance on the pads. All in the M ohms.

So what now? bad tubes or transformers which resistance wise seem to measure the same.

If i got another P board i am worried it may be in the tubes and kill it as well, not going to waste too much money or time on it but for learning i would not mind having a bit of a go.

[tom66]

Re: PANASONIC TH-L19X10AK LCD - will not start.

When replacing the transistors you must be careful to match Qg and Tr/Tf. Also it is advisable to replace all in a particular bank, as devices out of sync with each other will cause other devices to fail earlier.

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

When replacing the transistors you must be careful to match Qg and Tr/Tf. Also it is advisable to replace all in a particular bank, as devices out of sync with each other will cause other devices to fail earlier.

Ok now your getting tricky. I assume we're talking switching times.

the subs were tpc8118 for the 8119
tpc8032 for the 8037.

Never did bother replacing the SSG4407 and it's had a fair amount of use with no issues or any signs of trouble.

Now all of a sudden both failed? I was thinking something else may have deteriorated and drawing too much current.

Used a mosfet cross reference and they came up as suitable plus a long list of others.

What do you think of the match?

[tom66]

Re: PANASONIC TH-L19X10AK LCD - will not start.

If one transistor fails, then the other in a series chain will likely fail, this could also lead to the failure of all of the devices in the bridge (any in parallel.)

It is not necessary to make an exact sub if you replace all of them at once.

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

If one transistor fails, then the other in a series chain will likely fail, this could also lead to the failure of all of the devices in the bridge (any in parallel.)

It is not necessary to make an exact sub if you replace all of them at once.

Well i know with the original failure only the P channel failed and the n was good. P channel replaced only it worked fine for months then suddenly the N was really fried up and carbon everywhere, P also failed.

there's only 1 of each.

replacing both at once it fires briefly but you can see it must have a high current draw with both heating up quickly to failure point.

replaced them twice now with same result and at a total loss as to what is the issue.

Q7801,7802 in the picture

[tom66]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Controller IC's probably had it from too many drain-gate or source-gate shorts.

[aussiegreg]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Gents,
Replace Q7801, Q7802 , and most importantly C7801. The Cap should be replaced with a a hi temp, hi frequency equivalent. The Cap will look OK and may measure the correct capacitence but I'll bet if you measure it's ESR it will read high.

Cheers
Greg.

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Gents,
Replace Q7801, Q7802 , and most importantly C7801. The Cap should be replaced with a a hi temp, hi frequency equivalent. The Cap will look OK and may measure the correct capacitence but I'll bet if you measure it's ESR it will read high.

Cheers
Greg.

Thanks for the info, sadly I think I binned this TV as the replacement FETs kept burning up. Gave up.

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Gents,
Replace Q7801, Q7802 , and most importantly C7801. The Cap should be replaced with a a hi temp, hi frequency equivalent. The Cap will look OK and may measure the correct capacitence but I'll bet if you measure it's ESR it will read high.

Cheers
Greg.

Thanks for the info, sadly I think I binned this TV as the replacement FETs kept burning up. Gave up.

Well, turns out I do still have this TV. Bored and quite frankly not expecting much since I'm over this TV for a while now thought I'd have another look with the new info.

For the replacements I already tried tpc8118 for Q7801(TPC8119),
tpc8032 for Q7802(TPC8037).

So took them out and surpised they had not failed. So I followed Greg's advice and replaced C7801 but I only has a 220uf not 100uf.

Another thing I noticed was R7801 and R7805 for those Transistors are 47K in the schematic and parts list. On the board R7801 was only a 10K resistor, so I changed that to match the diagrams.

I tried it and got the familiar continuously flashing green LED, brief flash as it tried to fire the backlight.

I've always wondered if the tubes were part of the issue, so I had a set I stripped from another dud Sanyo 24" and plugged them in. What I found was 1 inverter cct would briefly light one of the tubes, the other dead. Then I tried another tube on the dead one , same.

Then out of the blue it fired and stayed on

Anyway I wondered since I had used a larger cap if that was it but once that first startup worked I hooked up the original backlight and it still works. I managed to find a 100uf and put that back in.

Still working and currently running it to test it at full brightness.

No unusual smells or burning, FETs seem cool enough.

With that CAP, this is weird for panasonic but all caps were NICHICON, and maybe 1 RUBYCON 105degrees, but C7501 was a JAMICON 85 degrees!

Unfortunately, dust has gotten in behind the panel, anyone know where I put the screws and key panel?

Thanks Greg. (Aussiegreg)

[martino]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Well, turns out I do still have this TV.

That's funny,are you like me,where there is a stack of around 40 tv's around you and once in a while you discover one you can't remember?
Working on one right now where I gave up a year ago chasing a YFR problem on a sustain board.Couldn't figure it out back then....Now within 5 minutes found the cullpit....

Congrats on the fix...

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

That's funny,are you like me,where there is a stack of around 40 tv's around you and once in a while you discover one you can't remember?
Working on one right now where I gave up a year ago chasing a YFR problem on a sustain board.Couldn't figure it out back then....Now within 5 minutes found the cullpit....

Congrats on the fix...

Don't tease me, 40 TVs? I should be so lucky. I have 0 to work on now except this pathetic 19" Panasonic. Picture is horrible compared to the PDPs.

Thanks, early days. Was just trying to figure ot how to get the dirt out of the backlight area, amazing how crap got in there, but I gues when you have a TV laying down with the back off with a years worth of crap landing on it I deserve it.

popped the frame off, saw the tabs and stuff it, it'll do not risking stuffing this after all this.

I was really bored though.

I have boxes of crap and boards everywhere.

This one I had written off, If it was a crap brand i would have binned it, nearly did.

[martino]

Re: PANASONIC TH-L19X10AK LCD - will not start.

I you weren't so far away,I would send ya a couple to keep you from getting too bored...

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

I you weren't so far away,I would send ya a couple to keep you from getting too bored...

Maybe you could build a raft and ship them. I'll take the chance with the sea currents.

This thing is still running touch wood. Took me 3 hours of box shoving , dust sucking, to find all the bits. Some screws missing but lucky I'm a hoarder, had a bag oLG screws which covered the ones missing nicely.

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

I was just googling the part number from the manual for the 100uf 25v jamicon cap,
F2A1E101A134

And low and behold get hit with a service tip, russian site and you need to join to download it but the post says this.

"Finalization of the inverter when re-entering a field effect transistor Q7801 Countermeasure for Power Stop Symptom: LED BLINKING Cause: No power due to Q7801 & Q7802 (standby-power stop) Applied Model: TH-19X10 SERIES Applied Chassis: KM02 Countermeasure: To protect Q7801 and Q7802 from surge voltage. a. Change R7801 from ERJ6GEYJ473V to ERJ6GEYJ103V To protect Q7801 and Q7802 part fail. b. Change C7801 from F2A1E101A134 to F2A1V221A470 (for life time) Market Actions: If market found Q7801 and Q7802 broken, apply the above countermeasure by replacing R7801 and C7801. Effective time: From FEBRUARY 21/02/2011. What's new in this version Chassis KM02 (View changes) POWER STOP KM02 L19X10 SERIES - from producer"


The irony here is, I noticed the descrepancy with R7801 being 10k compared to cct schematic of 47k. So I changed it to 47k.

Guide says change to 10k

I did not have a 100uf at hand so put a 220uf in , but later put 100uf in place.

Guides says use 220uf


http://www.kenotrontv.ru/forum/topic...E%D1%80%D0%B0/

[tw2005]

Re: PANASONIC TH-L19X10AK LCD - will not start.

another bulletin (India)

[gijareajay]

Re: PANASONIC TH-L19X10AK LCD - will not start.

Having Panasonic 19X10D model, if started after 2 to 3hrs set starts ok & continue with no problem. But if it is switched OFF and ON again green led blinks n become stable but no screen appears. Also no SOS/Red indicator flashes. Replaced C7801 100uf but symptom remains same. Any solution.

[gijareajay]

Re: PANASONIC TH-L19X10AK LCD - will not start.

I also tried with modification of 220uf but problem persists. Pl guide