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Crumbtrail TV Forums: TV Equipment: Plasma TV Forum:
LG 50pg20 -need help troubleshooting cause of death

 

 


hautewheeler
New User

Nov 17, 2011, 12:19 PM

Post #1 of 11 (7653 views)
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LG 50pg20 -need help troubleshooting cause of death Can't Post

Hi guys. I have been reading here, and appreciate all of the information on this site. I am diving into my first ever tv repair project, and need a little assistance from someone with more exp & knowledge that doesn't mind sharing with me.

this is a dead 50" lg plasma that I bought to tinker with and learn on, and hopefully restore to working condition.

Physically: outside:
casing front and back, flawless. no evidence of dropping or jarring, water damage, burn marks etc..

Physically: inside:
I have inspected all of the boards visually, and they all seem to be good physically; no staining, no bulging caps, leaking caps, nothing APPEARS to be burned out, (no scorching) all fuses are correct and are working properly. all cables appear to be intact, no bent pins, or loose connectors, or broken wires.

Testing what I know:
I have power from the transformer to the power supply. I have power from the power supply to the ysus and zsus boards, vs and va and +5 reads out at what is stated on the label (60v, 194v, and 5v - respectively).
-after that, I'm not sure how to test power out of the ysus and zsus, and not sure how much voltage I should have to indicate correct operation.

Indicators: outside: no humming or buzzing, or crackling.
when the unit is powered up, I hear a (relay?) on the power supply board click. the light on the power button comes on red. when you press power, it turns blue and then blinks 3 times and stays on blue.
-nothing from the screen at all.

Indicators: inside:
I have 1 led that comes on green on the control board (there are three, the middle one illuminates)

there are two led's that light up on the main board, one comes on red when standby, and then changes to red/green when powered up. the other led on the main board comes on green for about 5 seconds and then goes off.

-that's all I know, can someone smart point me in the right direction of what to try next?
thank you in advance guys, for looking, and for any help!



jts1957
Veteran


Nov 17, 2011, 10:57 PM

Post #2 of 11 (7643 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post


Quote
all fuses are correct and are working properly


Did they blow again after you replaced them the first time?Wink


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Location: Far, Far Away


hautewheeler
New User

Nov 18, 2011, 12:19 AM

Post #3 of 11 (7641 views)
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Re: [jts1957] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

No, sir.. they were not blown to begin with. (until I had a mishap with the multimeter probe and was very thankful that they were there.) I had to replace one because of my own oops.Blush

Haven't blown any since (high voltage and too much coffee doesn't mix, kids.)

I see varying voltages on the ysus board, where it meets the (I'm guessing) buffer boards? I'm not sure what these should be reading, or even if I'm testing the correct areas.

just wondering where to continue diagnosis


jts1957
Veteran


Nov 18, 2011, 1:42 AM

Post #4 of 11 (7639 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

http://elektrotanya.com/...al.pdf/download.html


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Location: Far, Far Away


hautewheeler
New User

Nov 18, 2011, 11:01 AM

Post #5 of 11 (7634 views)
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Re: [jts1957] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Thank you very much, jts1957 - that's just what I'm looking for, some education!

I'm gonna read this, see what I can figure out, and be back to report my findings!


hautewheeler
New User

Nov 18, 2011, 8:30 PM

Post #6 of 11 (7630 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Okay.. First of all, thanks again, jts1957. super helpful link.

I think I have it narrowed down to the control board. the manual shows a test for the board, and it does not test as good.

now, coming from the power supply, the vs and va voltages check out correct, but on the 5v out, I actually have 5.62 - 5.63 volts output depending on which set of connectors you test from. is this going to make a difference? I have already ordered the t-con (control) board, and I want to make sure that this is not the reason why the original failed before I install the new one when it gets here.


jts1957
Veteran


Nov 19, 2011, 1:59 AM

Post #7 of 11 (7626 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Unless you find something contrary in the service literature, usually +/- 20% is sufficient.Cool


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Location: Far, Far Away


hautewheeler
New User

Nov 19, 2011, 12:11 PM

Post #8 of 11 (7623 views)
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Re: [jts1957] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Okay, thanks jts1957. it had me slightly concerned because I found an adjustment for vs and va, but not the 5v.

are there any common causes for the ctrl board to fail? it has the least amount of components, and most of them are ic chips. seems like this would usually indicate degree of stability.

I know the board has failed, but just looking for ways to find clues as to what caused the failure. any ideas?


jts1957
Veteran


Nov 19, 2011, 12:26 PM

Post #9 of 11 (7621 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Anything from capacitors or ICs failing, a voltage spike or surge, a static discharge; to cosmic particles or photons, neutrinos, and muons or the like.


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Location: Far, Far Away


hautewheeler
New User

Nov 24, 2011, 12:34 PM

Post #10 of 11 (7598 views)
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Re: [jts1957] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

well, that didn't work.. back to the manual for some more troubleshooting.


jts1957
Veteran


Nov 24, 2011, 1:09 PM

Post #11 of 11 (7599 views)
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Re: [hautewheeler] LG 50pg20 -need help troubleshooting cause of death [In reply to] Can't Post

Make sure you didn't get your replacement part from, for example, defective boards 'r us (pulled from a working unit, 100% fully tested) etc.Crazy


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Location: Far, Far Away

 
 
 


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