Skywotrh LCD-32L29 stuck on standby

[s_henya]

Hey guys,

Got this 32" LCD TV today
its stuck on standby, without any response from the panel,
just the red standby led lights.

opened up the case without any visible faults,
the owner said it was fixed a couple of years before.
i can see that a few of the caps on the power supply were replaced.

voltage testing on power supply were good, 24.5v 12v 5v

any suggestions before i try checking capacitance for each caps in the power supply?
(esr testing in circuit was ok)

[tom66]

Re: Skywotrh LCD-32L29 stuck on standby

If power supply voltages are good, no point in trying to repair power board because it's fine. The fault will be on the main board.

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

Hey tom thanks for replying,

just to verify my readings are fine:
Power Board: 5800-P32TTN-W000

CN301:
pin1 ENA 0.098
pin2 ADJ 0.195
pin3 NC
pin4 GND
pin5 GND
pin6 GND
pin7 GND
pin8 GND
pin9 +24 24.5
pin10 +24 24.5
pin11 +24 24.5
pin12 +24 24.5
pin13 +24 24.5

CN302:
pin1 EAN 0.098
pin2 ADJ 0.195
pin3 GND
pin4 STB 3.25
pin5 GND
pin6 5VSB 4.95
pin7 GND
pin8 GND
pin9 +12 12.04
pin10 +12 12.04
pin11 GND
pin12 GND
pin13 +24 24.5
pin14 +24 24.5

CN303:
pin1 (+5v) 4.94
pin2 (+5v) 4.94
pin3 GND
pin4 GND

Is this normal?
if not, anything worth testing,
(all the ele' caps were good capacitance & esr)

if it is, some tips on checking the logic board?

[tom66]

Re: Skywotrh LCD-32L29 stuck on standby

Everything there looks fine. You can check volt regulators:
https://www.badcaps.net/forum/showthread.php?t=22231

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

so start testing voltage regulators on logic board?

[tom66]

Re: Skywotrh LCD-32L29 stuck on standby

Yes.

[munirutech]

Re: Skywotrh LCD-32L29 stuck on standby

what did you call logic board in lcd tv

[newtothis]

Re: Skywotrh LCD-32L29 stuck on standby

Main board, one with the inputs on

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

i noticed there is a led on the tcon board,
upon pluging in the ac, the led lights with blue color.
after a few sec it shuts off.

when i started testing voltages on the logic board
(second pic from the left from the first upload)

i could hear a faint buzzing sound and the led lighted again for a few secs,

i was very carfull not the short anything, and im sure i didn't,
any explanations?

[tom66]

Re: Skywotrh LCD-32L29 stuck on standby

The main board isn't sending out the inverter on off signals. No point in focusing on the t-con. The fault will be on the main board. You could completely isolate t-con board for now.

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

Logic Board 580G-A8M651-0000

Voltage regulators:

U5: 17-33
PIN1=0
PIN2=3.31
PIN3=4.95

U702 17-18
PIN1=0
PIN2=1.79
PIN3=4.95

U6 17-33
PIN1=0
PIN2=3.31
PIN3=4.94

U8 AS1117L
PIN1=1.37
PIN2=2.62
PIN3=4.94

so im guessing U8 is BAD?

[tom66]

Re: Skywotrh LCD-32L29 stuck on standby

U8 is fine: there is 1.25V between ADJ and OUT.
You probably have corrupted main board firmware, which would require new flash chip or new main board.

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

missed a big one
U24: L7805C2T
PIN1=10.55
PIN2=0
PIN3=5.02

any last tips before starting to search for new board?

[budm]

Re: Skywotrh LCD-32L29 stuck on standby

"U24: L7805C2T
PIN1=10.55
PIN2=0
PIN3=5.02"
That 5V reg. is fine.

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

so all the voltage regulators are fine,
isn't there nothing else i can test on the logic board?
i didn't find a replacment board anywhere,
and it would be a shame to give up now.

by the way after a while its plugged i can hear a buzzing noise and the tcon led
lights for a few secs,

could it be bad connections?
or bad buttons control board? (i have no remote for it)
i remember i read somewhere here about a trick to turn it on with a resistor.

thanks again for all the helpers :-)

[s_henya]

Re: Skywotrh LCD-32L29 stuck on standby

Solved!

fixed some cold soldier points on the logic board

on 2 caps 1 coil, 2 24v+

now its up and running excellent!

many thanks for all the helpers!