Lg Plasma Power Supply Help needed.

[happyade123]

Hi all. I joined this site quite a while a go, but due to some lingering health problems, the most recent and most prominent being a stroke and a hole in my heart that needed patching, I have not frequented the site as much as I would of liked. After a long recovery I am finally wanting to have a go at fixing some tvs and would appreciate any help and or support I can get.
I have been fixing Electronics for around 15 years but mainly Crt tvs and the like. I would like to branch into the newer technology ie Plasma, Lcds etc. I have all the basic Tools Including A Multimetre And a Soldering Station But I Dont Own An Oscilliscope Yet.
The tv I am choosing to work on first is a 60 inch Lg Plasma that was donated to me. Its model is 60PK550. I have tried to benchtest the power supply but the only voltage I have is approx. 3- 4 volts on the standby pin.
No relays click and all fuses are fine as are the 3 Ceramic 10 ohm Resistors. I have blanket soldered the entire board. I am thinking maybe IC 701 is giving trouble but only an educated guess. The Power supply number is EAY60968901. I have included pictures of the power supply. Pls let me know if you require anything further. Many thanks for your help in advance. Adrian

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Hi happyade123 I too had a stroke a number of years ago but it only affected my eyesight and concentration. You need a bit more basic info such as is standby led showing on, and what is voltage on legs of main capacitor/s on psu, can the PSU be forced on, what happens if y and x boards disconnected etc. Happy hunting!

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Thanks Maxvalutech. I have the power board out on the bench but when connected to the tv the red Led would come on but neither the remote power channel up or touch power on the tv etc would cause it to come to life. I have placed the resistor from the standby to the relay on and also from standby to M on as advised in a manual.Nothing happens though no clicks or anything and the only voltage is the 3 to 4 volts on the 3 pins connected with the resistors. When the board was in the tv I disconnected the Y sustain and X sustain boards (Might have the wrong letters lol) and still nothing. I noted when I disconnected the main board connection from the power supply would click the relays 3 times but still nothing then it would not do it again until a period of time had elapsed. Thanks. Hope this is what you need.

[mmartell]

Re: Lg Plasma Power Supply Help needed.

I think some supplies need a load across the output to fully come out of standby.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Mmartel I also had a lightbulb jig loaded on the vs and ground.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

I'm not well up on LG plasma sets but the voltages are the lifeblood and the presence or not of Vs and Va needs to be established. Protection circuitry may well turn set off within a second or two as it trys to start (relay clicking?) so test equipment needs to be in place and monitored immediately set switched to on. In later models disconnection of Y or X may well trigger a shutdown too.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Maxvalutech, there are no relay clicks at all and the power supply is being bench tested with a lightbulb jig I made up for this purpose. I have a 100 ohm resistor between standby and relay on and another between standby and M on. The only voltages worth noting are the 3 to 4 volts on the standby and the M on and the relay on when power is applied. There is a nominal 2 volts on the main filter capacitors which does not fluctuate so I doubt it has anything to do with protection but again I am still a novice with these things.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Sorry but unable to read connector info a better overhead shot including all connectors would assist. Also, main caps should be measured for voltage between the legs neg on neg pos on pos and should be up around 350/400v and if you don't have that working first there is no point in other testing. I take it the light bulb doesn't light up and M on is LG reference for Vs on?

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Attatched pics of the P813 connector closeup as requested Maxvalutech.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

I've had a look at service manual which wasn't very good I must say but it did say standby voltage is 5v whereas you report 3 to 4v . Earlier you posted red standby light was on which tends to indicate main caps OK so those caps should be verified first. If all that OK then forcing rlon first then do a check of voltages followed by Mon should produce something to measure. There is an error detect circuit.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Yes Maxvalutech, I too had looked at the training manual for it and it said it is about 3.42 volts in standby(Which I am getting) and 5.14 when running. I have been trying it again and again, and every so often the relays will click in them click out and then the Filter capacitors will then reach 330 volts, however most of the time the relays don't click and the voltage remains at a nominal 2 volts on the capacitors as stated earlier. I have forced the relay on via a resistor and the M on via a resistor as stated earlier also but to no avail.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Well in my view the problem with your PSU is at the very front of the power circuit as you should have around 350v on the main caps at all times power is connected. I would like to hear from others on this as my experience of plasma is mainly Samsung but I don't understand how you get standby voltage from that unit with those caps not working. I do have an LG 42PT250 on my bench and the two main caps measured together show 348v at standby.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

What power supply is in your Lg 42PT250 Maxvalutech?
I am thinking the startup resistors must of gone high but I can't seem to find them (stroke messed with my head).

[budm]

Re: Lg Plasma Power Supply Help needed.

Can we get CLEAR straight shot pictures of the whole top and the bottom side of the power supply board?

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Sorry Budm will see what I can do to sharpen them up a bit.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

There you go Budm. Hope this is sufficient.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Miners is older EAY62170901. From other posts IC701 mentioned plus 3 white resistors top rhs if one bad replace the three. But budm is the real guru and should get you on the right track. Those pics should be from directly overhead the board not slanty.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Checked those resistors ages ago thanks Maxvalutech. Ic 701 was my hunch from the beginning but if the ic is not getting its vc I keep thinking that it wont work anyway.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Here is a better view of the back of the power board (I hope).

[budm]

Re: Lg Plasma Power Supply Help needed.

I cannot help you with those LOW RES not straight shot pictures, sorry. I do not have the board in front of me to trace out the circuits.