Sharp LC-47SB57UT will not power on

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

Ok SMD means surface mounted device 8 pins - 8 legs- 8 solder contacts
See pic - what is the part number SMD in the cream square

According to the parts list, that is IC902 part# "IC LD7522PS SOP-8". I could just make out D7522PS. The other is IC901 part# "IC ICE2PCS02G PG-DSO-8". According to Google Images, it looks like it is supposed to have a crater in it.

[selldoor]

Re: Sharp LC-47SB57UT will not power on

Data sheet is here http://www.datasheetdir.com/LD7522PS+PWM-Controllers

Crater probably signifies the position of pin1


Pfc controller http://www.google.co.uk/url?sa=t&rct...,d.d2k&cad=rja

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

Data sheet is here http://www.datasheetdir.com/LD7522PS+PWM-Controllers

Crater probably signifies the position of pin1


Pfc controller http://www.google.co.uk/url?sa=t&rct...,d.d2k&cad=rja

Do you suspect one or both of these to be bad?

[budm]

Re: Sharp LC-47SB57UT will not power on

Check fusible resistor R922, R938, R924 to see if they are open.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

None of those three resistors are open.

[budm]

Re: Sharp LC-47SB57UT will not power on

Then I would try replacing those two startup caps we have mentions to see what happen.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

Will do, I have to look at my wife's van immediately after work while it's still light out, I'll post back with results after 6:00 central time. Thanks to everyone that has offered advice.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

By the way, the capacitor's that were suggested to be changed are
10uf 50V
100uf 50V

Locally, I can get
10uf 100V
220uf 50V

I was told that these would work. Is that true? If not, I can scavenge from a working power supply or order new and wait.

[tom66]

Re: Sharp LC-47SB57UT will not power on

The 100V is fine but you should try to find a 100uF cap.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

ok

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

Got the van taken care of early. I put the 10uf 100v cap in and swapped 100uf 50v caps from another working psu. The other psu still works. This one still does not. Same exact symptoms.

[tom66]

Re: Sharp LC-47SB57UT will not power on

Wait, where did the second PSU come into it?
I'm really lost...

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

It came from an lg 37lg30 with a cracked screen.

[tom66]

Re: Sharp LC-47SB57UT will not power on

They are compatible???
Since when has LG used Unihan parts???

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

I pulled a capacitor off of each psu with the same 100uf 50v rating and swapped them. I then put each psu back into their respective tvs. The lg still powers up, the sharp still doesn't.

[tom66]

Re: Sharp LC-47SB57UT will not power on

Oh, ok.
Time to look elsewhere.

You have fluctuating 5V standby?
So, do you have other fluctuating rails?
We had a 50" LG plasma here with fluctuating 5V, dead 12V. Turned out 12V diode was dead short.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

I'm not sure what fluctuating rails are, but no other pins fluctuate. If I knew what was driven from the PSU to the main and from the main to the PSU, I could probably temporarily retrofit a known good PSU with the same outputs/inputs (if one exists and happens to be in my basement) to the chassis, just to confirm/disprove a PSU fault.

I've been looking though the service manual, trying to find the answer but I'm not experienced enough to be able to spot it right away. Any chance one of you could browse these?

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

In the attached picture called "flags", what do the circled flags represent?

[tom66]

Re: Sharp LC-47SB57UT will not power on

Nets... they indicate connections to each other (with the same name) done to make the schematic a little clearer.

[johnboy1313]

Re: Sharp LC-47SB57UT will not power on

That's what I figured. Thanks