Sharp LC-60LE741E - No Power

[Strudul]

TV suddenly decided it didn't wanna turn on.

I've got no continuity across the fuse F7001, so that's gonna need replacing, but wondering what else I should be looking out for beforehand to avoid it potentially immediately blowing again.

Does anything look suspect on the attached image or are there some more continuity checks I should attempt first?

Cheers

[nomoresonys]

Re: Sharp LC-60LE741E - No Power

Start with checking all the diodes and resistors on the top of the board, duckgo search and youtube are your friends if need to know how.

[Strudul]

Re: Sharp LC-60LE741E - No Power

Start with checking all the diodes and resistors on the top of the board, duckgo search and youtube are your friends if need to know how.

The highlighted diode (D7805) seems to be shorted.

Also found this manual.

[nomoresonys]

Re: Sharp LC-60LE741E - No Power

Ok, suppose the easiest way is too take it out and retest it, to confirm, if read short out of circuit, pop a new one in and give it a go.

[Strudul]

Re: Sharp LC-60LE741E - No Power

Ok, suppose the easiest way is too take it out and retest it, to confirm, if read short out of circuit, pop a new one in and give it a go.

The diode was short out of circuit. Replaced it and the fuse, plugged it all back in and the fuse immediately blew again.

Bit lost on what next now.

[Strudul]

Re: Sharp LC-60LE741E - No Power

It does appear all pins are shorted on the rectifier bridge BD7001, but not sure if this is a symptom or cause?

[Donny2derby]

Re: Sharp LC-60LE741E - No Power

Measure for a short at your incoming? If there’s a short there then at least you know what you’re dealing with.

Can you find a schematic for it?

[Donny2derby]

Re: Sharp LC-60LE741E - No Power

There’s a few components on there I’d be looking at as well. Hard to be sure as it’s not perfectly legible but capacitor C7138 looks to be slightly ruptured as well?

[Strudul]

Re: Sharp LC-60LE741E - No Power

Measure for a short at your incoming? If there's a short there then at least you know what you're dealing with.

Can you find a schematic for it?

Where would be the incoming?

I can't find a schematic, but looks like like repair kits are sold for this issue which include the following components, but no information on actual part numbers:
F7001, BD7001, D7805, Q7801, IC7801, C7817, Q8700

There's a few components on there I'd be looking at as well. Hard to be sure as it's not perfectly legible but capacitor C7138 looks to be slightly ruptured as well?

Not sure I can find a C7138. Whereabouts are you looking?

I've attached some potentially better pics.

[Strudul]

Re: Sharp LC-60LE741E - No Power

It does look like this is short too, which is Q7801.

[Donny2derby]

Re: Sharp LC-60LE741E - No Power

Where would be the incoming?

I can't find a schematic, but looks like like repair kits are sold for this issue which include the following components, but no information on actual part numbers:
F7001, BD7001, D7805, Q7801, IC7801, C7817, Q8700


Not sure I can find a C7138. Whereabouts are you looking?

I've attached some potentially better pics.

Your mains power incoming. Marked Ac at the top of the board. If you have continuity across live and neutral there then you're definitely chasing a short and that's what's taking the fuse out instantly.

On closer look at that picture it's cap C7130 and looks ok actually.

What test equipment do you have? A multimeter? Semi conductor analyser? ESR meter?

Do you know how to test diodes/caps etc? Not trying to be difficult but it helps others to know what your abilities are.

[Strudul]

Re: Sharp LC-60LE741E - No Power

Your mains power incoming. Marked Ac at the top of the board. If you have continuity across live and neutral there then you're definitely chasing a short and that's what's taking the fuse out instantly.

On closer look at that picture it's cap C7130 and looks ok actually.

What test equipment do you have? A multimeter? Semi conductor analyser? ESR meter?

Do you know how to test diodes/caps etc? Not trying to be difficult but it helps others to know what your abilities are.

No short between L and N attached (with fuse F7001 currently in blown state).

Only got a multimeter.

I can test diodes (check continuity in each direction: should be no short, infinite resistance one way, and some (typically around 500) the other).

Not sure on caps. Can measure voltage, but not sure that helps?

[Donny2derby]

Re: Sharp LC-60LE741E - No Power

Having an ESR meter is best to be certain on caps but if you put your meter to ohms and test leads across the cap it should begin to climb to show that it’s charging. It’s not perfect to do it this way but gives you a good indication.

Try replacing the fuse with a good one and without powering up check for continuity again. But no continuity on there just now suggests there’s no dead short. Probably a faulty component giving an earth fault then. Needle in a haystack and requires testing each component individually.

Lovely stuff!