Dead Sharp Aquos LC-32LE430E

[borstar_micke]

My 12y old daughters tv (that she got after her grandpa, has sentimental value to her) was just dead without stby light a couple of weeks ago.

I´ve repaired a couple of computer monitors, classic blown capacitor replacements, a 55" Sammy led with t-connboard replacement and a 42" Panasonic edge led where I replaced the led-strip.

Not a master with the multimeter, which is cheap and 10-15year old btw...

So please make it basic...

To the issue at hand.

As stated, the tv is totally dead with no standby light.

Have measured on the power board and have 320V after the 3 capacitors on the hot side and also 320v by 2 zener diodes closer to the cold side (will add a photo of the power board). No voltage at all at the connector going to the main board or anywhere on the cold side.

Attached powerboard photo with the 2 diodes with 320v marked and the repair manual.

As you see I really need some advice here... stuck...

[Diah]

as i remember this power boards suffer from joint soldering points at Transformer pins.. so take it out of boards and check the down side and re solder all suspected soldering points

then put it in place and with reference to Tv chassis check the socket which goes to MB if any volts you can find on it.

[borstar_micke]

Ok,thx, will try that tonight!

[borstar_micke]

Melted a lot of solder joints, still no go...

[R_J]

The first voltage you need is the Standby +5.2V (page 127) see if it is there.

[borstar_micke]

No voltage AT ALL on the cold side...

[R_J]

You likely have a bad IC9301, pins 7~12 are hot ground, so using that as your meter ground, check the voltage on pin6 (320v), then check the voltage on pin1
On the back side of the board, check that ZD9301 is not shorted, then also check that R9325 (4R7Ω) is not open.

[borstar_micke]

Thanks for the help, greatly appreciated!

Measured IC9301; pin6 at 317v, pin1 at 0v

ZD9301 measured 003/003

R9325 I just cant seem to find... strangely only the 32" seems to miss the schematics of the B-side of the power board in the repair manual... also cant find ZD9301 or R9325 in the parts list for the 32"...

[Diah]

from yours measurements its look ZD9301 shorted. release one side of it from boards and measure it again... in case it had same read at both side / shorted.. mean there are R on the way open too.
so better upload focused high resolution photos to the top and down side of Hot area.

[borstar_micke]

It´s a smd zenerdiode so I´ll just remove from the board and measure both ways then?

[borstar_micke]

Removed and measured the ZD9301, now 762 / 1 so I guess that makes it ok?

Attached 2 photos of the hot side.

[R_J]

R9325 (4R7) is just above J9542 it connects the transformer feedback winding to D9311. (likely not your problem.
If you look at the schematic, ZD9301 should not read 003 (shorted), since it tests ok out of circuit, something else may be shorted, maybe C9312, C9316 or D9311
You can lift one end of J9041 which should isolate ZD9301 from C9312 this should point you to where the short might be.

[Diah]

i don't think there are any short.. its to me open circuit. of sure he tested ZD9301 with out discharge the hot section so the read 003

[lotas]

Most likely, the PWM is not working (3 pin is shorted from 4pin.), such a malfunction came across.

[borstar_micke]

Life got in the way, so I´ve first now had time to look at the board again.

Measured C9312 for continuity, gives a reading of zero both ways, indicating open circuit.

Also measured both sides against pin12 (hot ground) on IC9301, gives the same result.

Measured across C9311 which gives a reading of 1 both ways, indicating short circuit.

Against ground 1 one way and zero the other way.


Have also measured all resistors on the hot side which seems to be ok, and as good as I´m able too measured the other capacitors too and found C9816 that measures 1 both ways so also seems to have a short circuit.

ZD9301 is still not resoldered.

[nomoresonys]

Those are good pictures, can you post one of your multimeter, need to get consistent readings.

[borstar_micke]

Here is a picture of my old multimeter.

[nomoresonys]

That meter is fine for the job, the thing about meters that are not auto-ranging such as yours, is if you get a 1 it can mean out of range, as when checking in ohm mode, so say you are on the 200 ohm setting and get 1, you will want to move up to 2000 and recheck still 1 move up higher etc. Recheck all those you checked in ohm mode.

[R_J]

Originally Posted by borstar_micke

Life got in the way, so I´ve first now had time to look at the board again.

Measured C9312 for continuity, gives a reading of zero both ways, indicating open circuit.


Measured across C9311 which gives a reading of 1 both ways, indicating short circuit.

Against ground 1 one way and zero the other way.

Also measured both sides against pin12 (hot ground) on IC9301, gives the same result.

Have also measured all resistors on the hot side which seems to be ok, and as good as I´m able too measured the other capacitors too and found C9816 that measures 1 both ways so also seems to have a short circuit.

ZD9301 is still not resoldered.

Look at the schematic... If you have a short across C9311, either the cap is shorted or the optocoupler ic9312 is shorted (3~4), unsolder the optocoupler as it is easier and check for the short again. However if it is shorted, and you had standby voltage, the power supply would actually be ON all the time.

[borstar_micke]

Unsoldered ic9312, and c9311 still measures short, no continuity (both ways) while measuring in diode mode.

And I have no power at all on the cold side....