Lg Plasma Power Supply Help needed.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

I too had trouble getting clear shots with my phone camera at first posts. Have found a topside reasonably clear shot but underside also needed for tracing purposes. These power supplies must have given a lot of trouble as repair kits are advertised. I also read that LG very small caps were a problem so on yours I would check those near ac in and near main caps.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Bud M Pls tell me exactly what pictures you require and I will endeavour to get them. The only reason they are low res is I shrink them to make them quicker to upload and not take up much space but if you want me to keep them at full size then I will.

[budm]

Re: Lg Plasma Power Supply Help needed.

They have to be high res so I/We can zoom in and able to trace those copper traces on the board, basically so we can reverse engineering to figure out what the circuits are for each section of the board.
So: straight shot of the whole top side and the bottom side of the board.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

I hope this is better BudM , as I can really do with some help and I am prepared to do whatever you or anyone else needs to get it.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

OK I have replaced the 5 volt regulator and now have my 5 volt standby but still no other voltages except the times the relay clicks 3 times (intermittently) I end up with 350 volts on the 4 filter caps. Any other suggestions. I am leaning towards Ic 701 on the bottom of the board but it seems a real pain to remove and replace. Pls Help. Adrian.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Here is the service manual I downloaded the 50 and 60 use same circuitry.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Thanks heaps for that mate but typical of Lg as useless as tits on a bull.
One good turn deserves another. Here is the training manual I used for reference Maxvalutech. I don't understand why no one else is able to help. I thought I got high resolution shots of the board as requested.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Open to correction by others but with PSU out of set I think that with power connected and turned on at pp there should be constant 350v at main caps and 5v (3.3perhaps) at standby - nothing else. Connect standby to RL on and voltages of 17. 12. 5. should switch on. Then with load connected (light bulbs setup) connect 5v to M on (M for module which I'm assuming to mean plasma screen circuitry) and Vs should output.
When PSU is in the set and standby is present activating power up should result in main board sending RL on signal and M on signal to PSU .
Conclusion if PSU tests OK when forced on without connection to main board but does not react at least momentarily when connected to main board then main board or perhaps control board fault. If it doesn't test OK at force on then circuit hunting on PSU is needed to find fault/s.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

The only time the Capacitors have the full 350 volts is after the two relays have closed Maxvalutech.According to the guide this is the way it should be and I quote "When the Microprocessor IC1 on the mainboard receives "Power on"command it outputs a high 2.43v call RL_onsignal at pin 15 of P 813. This command causes the relay circuit to close both relays RL 101 and RL 103 routing Ac to the Bridge Rectifier , which then routes the primary voltage to the PFC.
Any more ideas welcomed. Thanks again mate.
Adrian.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

Well to have standby voltage it has to be derived from 240v ac and that has to be rectified with a constant voltage somewhere. In this case from training manual I see that fuse F302 (second one up from bottom) should have 158v DC on it in standby. Has it? The block diagram shows this whereas the pictorial one is incorrect. All that is really different to what I have outlined is that if PSU out of set then ac det would need to be jumpered on as well. Your posts are not explicit enough at this stage e.g. is PSU in or out of set , what have you done to turn PSU on, are the required turn on voltages for PS on M on Ac det coming up, and when PSU is on is 17v active, etc etc as unless this type of info is given the responses will be..........limited at best.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Sorry Maxvalutech but since the stroke my thought pattern is messed up and I have to wait for triggers to know what to type etc. Ask me specific questions I am happy to give specific answers.
Maybe this forum is not my best place to look for help but I thought someone might be able to point me in the right direction and possibly offer me triggers which stimulate my brain into thinking.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

How do I delete this entire post and I will start all over again giving as much detail as possible and will endeavour to get as detailed pics as possible that way there should be no controversy.
Cheers Adrian.

[maxvalutech]

Re: Lg Plasma Power Supply Help needed.

I think that's a good idea Adrian as you are better prepared now with what is needed. Regarding stroke problems I use brief notes as an aid to memory - nothing complex just something to remind me where I got up to or what is required. Of course with being 80 y.o. shortly I have a propensity to then lose my notes!!
On page 43 of the training manual regarding PSU there is given the 3 steps to test the unit once lightbulb load connected. Step A turns on the main caps from the auxiliary standby circuit - check the main caps get about 339v. Step B turns RL on for 5v and 17v which shoulbe checked as present and steady. Step C uses the 5v to turn M on which is Vs so lightbulbs should come on and that voltage should match panel sticker closely. If all that goes OK then the fault is elsewhere and be the subject of a discourse of what happens next. If the PSU doesn't have steady output at correct voltage then the faulty circuit should be indicated by what Step failed. In other words follow the step by step procedure.

[happyade123]

Re: Lg Plasma Power Supply Help needed.

Thanks Maxvalutech . Sorry for not doing it right the first time. Wow 80 years old. Gee I am only 45. I have a lot to learn and happy to glean knowledge off people like you.