LG 42PJ350 Starts, Shuts down, won't restart

[dkneyle]

Classic symptoms. Start up from cold OK. Runs OK for a period of time. Then starts to go into an auto restart routine. Eventually even this doesn't work and it just dops into the relay clicking on-off scenario. Disconnecting from the mains isn't enough to get it going again. It must be left for some hours before it will re-start and then repeats the same symptoms.
I'm assuming it's the power supply. All caps physically look OK.
Lots of clues out there on the interweb for the 'no-start clicking relay' type scenario, but not actually for my situation.
Before I start randomly replacing electro capacitors I thought someone might have a suggestion for me? I even read elsewhere on this forum that it could be the regulating IC acting up once it gets hot.
As always, good advice is much appreciated.

[martino]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Sounds like temperature related problem.
If you have a hair dryer and a can of air(to clean pc out etc) then you can pin point the problem relatively easy...
Start with TV cold,so it would work like you said,have back cover off TV,aim hair dryer at let's say the power supply board and heat it up,see if TV acts up,should be able to replica the fault in like a minute...
Once you found the board that reacts to the heat,you then take the can of air,hold it upside down and spray on parts of that board,the freon that now comes out of the can will freeze components,the temp sensitive part/area will reveal itself

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Thanks for the troubleshooting advice Martino. In fact I too was thinking of going down that line. Then I went looking for a can of spray freeze and was surprised at the cost. About $50. Still, the more I'm doing this servicing work I need to build up a supply of basics. Years ago when I worked in the telecommunications industry I had easy access to things like spray freeze and didn'tthink about it. No that I'm starting to move from hobbyist into professional tech repairer I realise that I have to have these things for myself. I'll let you know how I go. My guess from reading other posts is that it's the regulating IC.

[tw2005]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Thanks for the troubleshooting advice Martino. In fact I too was thinking of going down that line. Then I went looking for a can of spray freeze and was surprised at the cost. About $50. Still, the more I'm doing this servicing work I need to build up a supply of basics. Years ago when I worked in the telecommunications industry I had easy access to things like spray freeze and didn'tthink about it. No that I'm starting to move from hobbyist into professional tech repairer I realise that I have to have these things for myself. I'll let you know how I go. My guess from reading other posts is that it's the regulating IC.

A cheap can of air inverted will generally do. Maybe $8-10

[martino]

Re: LG 42PJ350 Starts, Shuts down, won't restart

I use just a plain can of air,they are cheap,like 8 bucks here in Canada...They don't really last too terribly long but enough to do several trouble shooting projects...Didn't know the official freeze spray was that costly,wow....

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Well, the story moves on. It was re-sarting after cooling all OK. So it came time to remove the power supply board and have a closer look. I did nothing to the board. I put it back in-situ and now it won't restart - just your classic relay clicks. Anyway, this may be a good thing because at least now the fault is there all the time.
There are repair kits available on E-Bay/Internet for this power supply board, and the components give a good clue as to the regular failing parts. I've been looking around the vicinity of the 6 terminal power regulator. Type 3BR1565JF. There is a Schottky diode (40V 1A) [type SD140 for anyone trying to track that part down] in parallel with a resistor (R305) which appears to be 0.36 ohms from the colour bands. Out of circuit the diode reads OK, and my meter doesn't have accuracy at that low level of resistance but reads 0.6 ohms so the resistor is probably OK (shows no signs of distress). But I'm a bit mystified how the diode does it's job if shunted by such a low value of resistance?
I'm going to order a replacement 3BR1565JF and see whether that brings it back to life.

[martino]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Double checked if all cables where plugged in correct??
When you froze the powerboard,could you pinpoint the area where it was temp sensitive?
Did you check the solder side to look for any bad solder joints?

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

I didn't get an opportunity to heat and freeze because it went into a permanent fail state before I could get to that step. The solder joints all looked good. I'm betting on that 3BR1565JF device as being the cuplrit. I'll report back when I have taken that next step.

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Replaced the 6-terminal regulating device 3BR1565JF and the set powered up no problem and has been heat soaked and continues to work OK. I looked at the data sheet for that device and the typical circuit shows a low value resistor used for current sensing that has a reverse biased diode across it. As I said above, both of these checked out OK. Purchased the device from Macau, landed in Oz for <A$5, and I probably paid too much anyway! So this plasma goes back into service for less than the cost of a hamburger. I suspect these devices have substitutes; I notice in another post a SMPS problem that seem to revolve around a 6-terminal regulator part number STW6765 which sounds very similar (but check first if you are reading this post).

[martino]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Nice repair.!! And thx for reporting your findings

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Just got one of these tv's same symptom. So replacing this works?

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

G'Day mate, we'll it worked OK for me. I got the device from China via E-Bay. Let me know how you go.

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Cheers I picked the setup for 20 dollars I thought it was stolen for a about 1 hour until it turned it self off.
from where I got it is a dodgy place.
I will order it seems like it has ur symptoms.

Gotta replace the Coax Plug on the mainboard. should be a simple fix, I will remove tuner from main and solder in a new rf plug.

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

I think I paid about $5 for that regulator chip. I'll be very interested to hear how you go. I believe the set I repaired is still going strong; it hasn't bounced anyway.

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Well that never worked took a 40 mins to turn off.

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

wondering if its these 5W22RJ resistors in this location R927 R929 and I hope my new 3BR1565JF hasn't shorted.

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

r929 22.03oHms
r927 22.00oHms

so not them guys..

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

Good news, bad news. We are on the right track. We know that the original 3BR156JF was dead. But now the replacement is also. Order another one of those. It failed in order to protect the 2c component somewhere else! I need to look at the circuit diagram, but I reckon there's a snubber diode somewhere close by that IC that has probably gone open circuit. You look around with your meter and I'll try to find it on the circuit diagram.

[dkneyle]

Re: LG 42PJ350 Starts, Shuts down, won't restart

--

[Amraks]

Re: LG 42PJ350 Starts, Shuts down, won't restart

The original one would do the samething.

It would go for 40 mins and shut down and it would keep clicking when turned off.

The snubber diode you are talking about tests bad in circuit but tests good out of circuit..
I will buy some freeze spray.