LG RT42PZ45V standby ok no start

[maxvalutech]

This old plasma going OK turned off with remote and a little later tried turn on red light to amber for about 10 seconds then back to red
Of course 5v standby is there but only 1.38v showing on 3.4v line and no 12v or 6v or vA or vs
Seems could be power board MPF7407 PCPF0030. Has anyone any input re this board as all caps etc look OK but its a large board
All fuses OK as well.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Hmmm comments as dead as the set??

[ReeceyBurger123]

Re: LG RT42PZ45V standby ok no start

Images of the boards please ?

[Alastair E]

Re: LG RT42PZ45V standby ok no start

Ancient 480/576p EDTV Plasma set--not many have seen 'em lately!

Prob one of its IPM's...

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Thanks for the comments. Yes about 12yrs old set but a favourite of a good friend. Was hoping to find something obvious or known. Did find service manual with schematics but Not including power board!!
Never seen so many components as in this set and difficult to see what relates where and why. Have pulled power board today and will run what component checks I can. Sorry re pics but only have basic android phone for inet posts etc and not sharp enough.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

No clicking when attempt to start so surmise no voltage getting generated which indicates to me problem is just in circuit area following standby which is OK. Have checked all diodes OK. Tried to upload pics but can only get to "choose photo" after which nothing happens (android phone)

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

A bit flummoxed with the following readings. There are 3 resistors in the ac inlet circuits being R001 and R010 banded brown black green gold green and one of these bridges out sides of the 2 x 8amp fuses which come off ac input. Nearby is also one banded gray red green gold green
My problem is the first 2 read 1meg ohms scale and I can't get the other to read at all on the 2m scale of my meter BUT the colour coding indicates only 10.5
ohms and 82.5ohms doesn't it !!???

[rockit711]

Re: LG RT42PZ45V standby ok no start

Are you sure those bands are right? If you leave off the last green of each resistor don't you get 1M for the first and 8.2M for next. making the first spot on, and would explain why the second doesn't show up on the 2M scale.

[dick_barton]

Re: LG RT42PZ45V standby ok no start

I would say they are 1Mohm and 8.2Mohm also using the fact that first two you mentioned do indeed read 1Mohm.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Yes I find it difficult to reason that they would go so high and still read per first three colour bands
The fourth gold band is supposedly the multiplier but that colour is for x 0.1 according to the resistor charts I called up. But a thread herein on lg power board refers to service manual stating these 3 wirewound resistors can be troublesome and the tech checked his board and found one open - he said he replaced the 10 ohm resistor!!! While that didn't fix that problem a photo of the board shows much similarity to the one I have and the resistor colours much the same!!! As well I have not seen such high range on power boards I have looked at but then again these are on the ac side at the fuses as mentioned earlier.

[rockit711]

Re: LG RT42PZ45V standby ok no start

Just seems far too coincidental that two read 1M , and leaving the band off results in a 1M marking. Remember if you leave the last band off its a 4 band code, so the third is multiplier (100000x) and the gold is error toleranxe (+/-5% from memory) if green isndeed right that's just .5%, relatively unusual to see that sort of tolerance.

Also even if the bands are accurate what are the chances 2 10ohm resistors would fail in such a way to cause their resistance to increase to 1Mohm each.

One thing worth asking is have you pulled the resistors from the board? As there could be other components that could throw off a resistance measurement on the board.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Have now located a site explaining that there are exceptions to general rule and that band 3 is multiplier and 5 is temperature qualifier. Means all looks to be OK but then I can't measure over 2meg with my meter. Off for eye op tomorrow so all set aside for a few days.

[rockit711]

Re: LG RT42PZ45V standby ok no start

Chances are the resistor is fine. If you really need to confirm it, desolder a 1M and the 8.2M put them in parallel and your meter should read around .888Mohm for the two in parallel?
Have you confirmed it is the power board for sure?
As someone said earlier its probably the IPM.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Now happy about resistors the other post led to my concern about 10ohms but he must have read the bands as I did. Not at all sure fault is power board but logical place to start. This heavy large set remains in situ at owners house. Main board is under shield and this is all taped together on set
IPMs on Y and Z boards I imagine - no experience with these so what simple test can I do on these and what is the fail likely to be (open or short or....) and does this call in protection circuitry? Assistance is appreciated.

[dick_barton]

Re: LG RT42PZ45V standby ok no start

Check the fuses for open circuit and check the resistance between the various supplies given on the board to Ground for short circuit.

On a board I have here the IPM module has the various supplies written against the pins (5V, 15V, Vss) so hopefully so will your boards.

[ReeceyBurger123]

Re: LG RT42PZ45V standby ok no start

Have you images or what ? Also do what DB suggested and start checking the fuses. If they are good its time to start checking voltages.

[rockit711]

Re: LG RT42PZ45V standby ok no start

on some(most?) Plasmas you can unplug the cables from the PS to the Y/Z sustain boards and if the TV doesn't go back to standby or give error codes etc and generates the correct voltages at the pins to the cable you just unplugged you can be pretty certain it was whichever board you had unplugged causing the fault. I know this doesn't work for some TV's but its a really easy check that only takes a few seconds.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Finally got back to this set. Set up dmm before turning on from cold. Main caps went to 386v relay clicked and other voltages came up until amber light went back to red. Main caps slowly discharged. Disconnecting y and then z boards no difference. Still seems like overheat component on power board may be problem. Any thoughts appreciated. Will try get pic of power board up.

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Pic attempt

[maxvalutech]

Re: LG RT42PZ45V standby ok no start

Well had to have eye op to remove cataract with another yet to be done so I can see out of one anyway. From tests done suggested to my friend that set was not worth spending much on but that power board was my best guess and could get one from China for $50 all up. It arrived today fitted it and all good. He now has set going so heres hoping! Purchase made via aliexpress and delivery just 3 weeks.