Sony KDL-32L504 No Power ....Dead

[Welchs101]

Hi, a neighbor asked if i could help fix their LCD TV. I like to "tinker" so i thought i would give it a try.

I am enclosing pics of the main power supply board and video board.

What i know:
When i plug in the power cord i do "hear" a click but TV does not come one. NO LED visible as well.

Any ideas on what to check? i did check the "fuses" on the power supply board but they look ok.....measure around 0.4 to 0.6 ohms.

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

Did the neighbour say how it went out - just wouldnt come on one day? or did it go bad over time?.
Whilst its not the same set as yours there are some tests in this thread - I dont fancy re stating them again so soon.
https://www.badcaps.net/forum/showthread.php?t=24114

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

just talked to neighbor.......dont know why i did not ask that question about how it went bad.........turns out they "think" it was a lightening strike that killed it.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

ok, so i read the link you posted.......now what? Most if not all the link talked about checking the fuse.......well i did that didnt I....fuse looked ok.

any suggestions on what else to check?

[budm]

Re: Sony KDL-32L504 No Power ....Dead

OK. on the top right of the power supply board, there is a white connector with multi-wire on it, can you take good close up pictures so we can see the voltage labeling on it? We need to find out if that connector has any DC voltages on it.

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

ok, so i read the link you posted.......now what? Most if not all the link talked about checking the fuse.......well i did that didnt I....fuse looked ok.

any suggestions on what else to check?

I think you will find most of the thread was about checking the voltage from
ac input on. Check the voltage at the connector, the fuse, the Bridge rectifier. Care as high voltage. AC. Then change to DC and check the DC out
of the bridge rectifier - often a casualty of lightening strike.

A quicker test if you can get to the terminals is to check the DC across the
BIG 400 / 450v cap/caps - again care as still high voltage.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i have not had time today to make any measurements but i will tomorrow. but i did take some pictures and i am posting them here.

in one of the pictures i highlighted in yellow two similar type devices. i dont remember what they are called but i do recall that such devices are used to convert AC to DC.........i think.

I did make a quick measurement of the resistance between the leads of each device...........on one device all the resistance measurements were in the MegaOhm range........for the other the two inner leads were shorted......is this a problem?

[budm]

Re: Sony KDL-32L504 No Power ....Dead

They are bridge rectifier, the two inner pins (they should have something like 'AC' or ~ on them to indiacte AC) are usually where the AC will be applied to. If it read short then more likely will cause the fuse feeding it ti blow.

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

Well at the risk of being accused of being sarcastic - you would have known that if you had read the thread I suggested you read.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i did a quick ohms measurement of the two bridge-rectifier looking chips. See enclosed picture where i identify the two with labels which will correspond to the measurements below:

Device1:
Pin1 to 2: 1.2MegOhm
Pin2 to 3: 1.3MegOhm
Pin3 to 4: 0.9MegOhm

Device2:
Pin1 to 2: 7.6kiloOhm
Pin2 to 3: 0.5Ohm
Pin3 to 4: ~1KiloOhm

When you look on the back of the board.......pins 2 and 3 should be shorted as they have an inductor i guess between the pads.....makes me wonder if the other readings are ok as well............

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

Those readings are not enough on there own- in the thread I keep harping on about there is this:
https://www.badcaps.net/forum/showpo...5&postcount=24

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

Device 2 appears to be on the secondary side of the board so on Device 1 can you carefully test for high voltages.
Can you perhaps update your profile with country and mains voltage then we will know what we are dealing with.
First set your meter on 600 VAC or autorange and check that you get mains voltage at the mains in socket. Next test for mains voltage on both sides of the fuse. Next test the centre pins on device one for mains voltage.
Change your meter setting to 600VDC and check the voltage on the outer + and - pins on device1.

[budm]

Re: Sony KDL-32L504 No Power ....Dead

That device2 (bridge rectifier) is for secondary side power supply, pin 2 and 3 are connected to the output winding of the transformer, so the DC resistance will be REALLY LOW which is normal when read in circuits.
See post 5 of what I requested.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i have updated my profile to include my line voltage and location. I will try and measure the voltages you mentioned once i get home from work.

oh, and i will read the link provided as well.

thanks.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

budm,

see post #7.........i took a picture of the white connector you asked for........does this answer you question?

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

selldoor,

Device1:
Pin1(red) to Pin2(black): 1.2MegOhm
Pin2(red) to Pin1(black): 0.6Megohm to 1.2MegOhm...started out at 0.6MegOhm and increased
Pin2(red) to Pin3(black): 1.3MegOhm
Pin3(red) to Pin2(black): 1.3MegOhm
Pin3(red) to Pin4(black): 0.9MegOhm
Pin4(red) to Pin3(black): ~0.9MegOhm


Device2:
Pin1(red) to Pin2(black): 7.6KiloOhm
Pin2(red) to Pin1(black): ~1KiloOhm
Pin2(red) to Pin3(black): 0.5ohm
Pin3(red) to Pin2(black): 0.5Ohm
Pin3(red) to Pin4(black): ~1kiloOhm
Pin4(red) to Pin3(black): ~1kiloOhm

[budm]

Re: Sony KDL-32L504 No Power ....Dead

Sorry, but no, the picture of the connector with wires in the way to be able to read the printing on the board.

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

Neither of the them seem right outer pairs should be off scale one way and less than 2000
the other ( at least that is what I believe)
Can you do the voltage test
First set your meter on 600 VAC or autorange and check that you get mains voltage at the mains in socket. Next test for mains voltage on both sides of the fuse. Next test the centre pins on device one for mains voltage.
Change your meter setting to 600VDC and check the voltage on the outer + and - pins on device1.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i am enclosing pics of the connectors. the pics are at an angle so if you need me to retake them just let me know.

i also measure the line voltage (prior to the fuse) and it was 122.5VAC

Then i measured the AC voltage on the center two pins of the bridge recitifier labeled in a previous pic as device 1.........and its voltage was 122.5VAC.

Was not sure what to measure "Change your meter setting to 600VDC and check the voltage on the outer + and - pins on device1. ".......which one is the + and which one the -

[budm]

Re: Sony KDL-32L504 No Power ....Dead

Your digital meter does not care about polarity, if it is reverse, it will just show the numbers with NEGATIVE sign in front of the display number. Since this power supply has PFC voltage booster circuit AFTER the output of the rectifier, if you check the DC at that large DC filter cap (it is connected at the output side of the PFC), it should have 165~170 when TV is plugged in without turning on, and about 390~400dvc when turn on.