Sharp LC-40LE830M no power

[chewbacca78]

Hi, i have a Sharp LC-40LE830M LCD TV that has no power now.

It was turning on and off by itself a few days ago. I pulled out the plug and left it there for 2 days. Then I plugged in last night and it's totally dead with no standby lights. I suspect it's the power supply and i'm trying to troubleshoot the components in the power supply and need some advice on which components to check. Thank you.

[ammarben]

Re: Sharp LC-40LE830M no power

a bad capacitors on the power supply can do that
find first the buggled capacitors

[chewbacca78]

Re: Sharp LC-40LE830M no power

a bad capacitors on the power supply can do that
find first the buggled capacitors

I already did a visual check on the capacitors but don't see any bulge in any of them. I did a search and read that some bad capacitors may not have a bulge but I'm not sure which capacitor should I start checking first if I have to remove them. any idea?

[mmartell]

Re: Sharp LC-40LE830M no power

If they're not bulged and they're not shorted you can't really test them without a capacitance meter or better still an esr meter.

You need to troubleshoot the supply. Make sure the fuse is not open then check the dc voltage at the large capacitor in Primary side but Be Careful as that is the deadly Hot side !

[mmartell]

Re: Sharp LC-40LE830M no power

Actually, scratch that last post since we're not even sure the power supply is the issue here. Check the pins at the mainboard harness from the ps for 5v standby voltage - if you have that but no lights in front then mainboard is likely the culprit.

[chewbacca78]

Re: Sharp LC-40LE830M no power

Hi mmartell, i repair printers but i'm a noob at tvs so please pardon my questions.

I attach pics of the PSU and mainboard. looking at the connector, do I measure the 5VDC on the metal part of BU5V? If I did it correctly, I got 0V on the meter for that.

[vinceroger69]

Re: Sharp LC-40LE830M no power

What voltage do you get at the pin marked stb?

[chewbacca78]

Re: Sharp LC-40LE830M no power

hi vinceroger69, where do I measure stb? Please see photos.

I also measure around the resistors and found one to be below reading. It's rated at 2M ohm but i measured around 1M ohm. Not sure if this is one of a few components that needed to be changed.

[newtothis]

Re: Sharp LC-40LE830M no power

Marked it with an arrow.

There are 2 rows of pins so it is the one on the lower row closest to the board

[chewbacca78]

Re: Sharp LC-40LE830M no power

i hope i'm doing it correctly. i measured the pin with the circle with my ground on the screw and i got 0VDC

[newtothis]

Re: Sharp LC-40LE830M no power

Can you confirm voltage at the mains input?

Meter at 600v VAC

[chewbacca78]

Re: Sharp LC-40LE830M no power

I'm from Singapore so reading i got from my mains is 230VAC.

[vinceroger69]

Re: Sharp LC-40LE830M no power

There is a white fuse with wires on by the mains input socket does that test ok?

[chewbacca78]

Re: Sharp LC-40LE830M no power

you mean the one circled in red? yes, hear continuous beep on my meter. However, the resistor i circled is rated at 2M ohms but i measured around 1M ohm. is this ok?

[newtothis]

Re: Sharp LC-40LE830M no power

It could be in parallel and read different in cct to out of cct.

Again VDC 600v , Can you put Red probe to + and black to - on one of the long capacitors. Careful high voltage.

[chewbacca78]

Re: Sharp LC-40LE830M no power

i measured both long capacitors and got 0VAC for both...am I doing anything wrong? Why is everything 0V??

[newtothis]

Re: Sharp LC-40LE830M no power

You have voltage at both ends of the white fuse you highlighted yes?

Can we have a photo of the underside of the board too so we can see the traces please

[chewbacca78]

Re: Sharp LC-40LE830M no power

yes, i did continuity check on the fuse and it's ok. it's not blown

[newtothis]

Re: Sharp LC-40LE830M no power

Can you just confirm voltage there too please, Just to rule out broken solder joints

[chewbacca78]

Re: Sharp LC-40LE830M no power

in ac?