Have a LG 37lh40 with a bad power supply EAX55357701/32 board. tv tries to light back lights but can't - cycles forever. took power board out and bench tested. has 5V, jumper pwr on to 5v and 12V good, 20V good. Have a second power board - it turns on tv - works perfectly, I have checked all caps (ESR), looked for bad solder, checked all xsistors, and no luck, anybody have any experience with these power supply boards ? thanks
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eax55357701 repair
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Re: eax55357701 repair
So does the backlights try to come on at all when using the bad board?
Did you check inverter transformers winding resistances and compared them to the working board?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: eax55357701 repair
put small wire on ic301 pin 14 - never moves off 0 volts. I had a good ground (used GRD on main connector - P201). assume the IC301 turns on inv lights (ON/OFF) ? have bad IC301 ?
windings resistance across output of inv xformer were: good board - 22.9 ohms each output - total across both 46.8 ohms
bad board - 26.7 ohms across both - 50.9 ohms
symptoms of set were that it would gradually take longer and longer to turn on (red led indicator on front bottom of set would turn solid blue led). It finally stopped turning on (led front bottom indicator never turns blue - stays red).
seems like main board is telling it to shut down. going to check voltages again on bad board in set.Last edited by ajshoe; 10-16-2019, 11:03 AM.
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Re: eax55357701 repair
In your first post you saytook power board out and bench tested. has 5V, jumper pwr on to 5v and 12V good, 20V good."
On the bad board what voltage do you have at Fuse F501 when you power up out of standby.Last edited by dick_barton; 10-16-2019, 11:28 AM.Willing to help but I'm no expert.
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Re: eax55357701 repair
earlier posts I was checking and reading voltages on bench. I tested them again on bench - they are correct and constant. The last posts were tested with bad power board in tv. I then plugged in set and then turned power switch on. took readings that I posted - voltages are varying. I thinking now that the power supply can't supply enough current on 12V. Can I load test the 12V and 20V line ?
also - I ohmed the pin 14 to inv on/off - it is good - 1K ohms on both boardsLast edited by ajshoe; 10-16-2019, 01:17 PM.
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Re: eax55357701 repair
The board only has one power transformer (LLM-001) to provide always on 5V Standby and the switched 12V, 20V, so you are indicating that the 12V and the 20V are not stable, so are you sure that the 5V Standby is stable since is generated by the same power transformer LLM-001 when connected back in the TV.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: eax55357701 repair
Is the variation of the 5V in sync with the variation of the 12V/20V?
May be try heating the power supply board with hair dryer to see all the Voltages will become steady or not.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: eax55357701 repair
installed new lm431 - to92 - made lm431 work. installed board and now have solid 5 volts. 12V and 20V come up but cycles to 0 about every 5 secs.
DC voltage at F501 is 377V but cycles to 250V every 5 seconds. observing IC301 pin14 inv on/off - never goes to 3VLast edited by ajshoe; 10-18-2019, 10:07 AM.
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Re: eax55357701 repair
It sounds like the PS-ON is going on and off.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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