Sharp LC-40LE810UN question

[tibimakai]

Re: Sharp LC-40LE810UN question

That small capacitor value is 22uf/100V and I'm measuring E=0.63/25.7uf.
On the connector of the meter it shows E=0.31.
I don't have this capacitor with 100V value, only 50V.

[budm]

Re: Sharp LC-40LE810UN question

Are you talking about the C7912 thay laying side way by the Standby transformer?

[tibimakai]

Re: Sharp LC-40LE810UN question

Yes the C7912.
D7913 it's OK.
All the FU resistors(are they fusible resistors?) show a value.

[budm]

Re: Sharp LC-40LE810UN question

I do not expect the DC voltage on that cap to be any higher than 25VDC at the most, but it looks like it tested OK. The spec of the IC indicates that the VCC should rise up to 18V and then the IC will send the drive signal to drive the Gate of the MOSFET which then the DC will be generated by D7913. You should hook up the meter across that cap when the TV is unplugged, then plug in the TV and see if the voltage will rise up to 18V or not. by the way. what is the resistance reading between the VCC pin of the IC and Ground?

[tibimakai]

Re: Sharp LC-40LE810UN question

I have lifted D7910 and I kind of messed it up, crushed the plastic. It still shows a value. I'm scared to lift it again to double check it.
It checked out OK when it was lifted.

[tibimakai]

Re: Sharp LC-40LE810UN question

There is no increase in voltage. Oscillates slightly, but it's around 5.9-6.1V

[tom66]

Re: Sharp LC-40LE810UN question

That diode is now dead if it's sustained that damage... it will likely be something similar to 1N4148W.

[tibimakai]

Re: Sharp LC-40LE810UN question

Yes you are right, it's BAS16 or BAW62 which is 1N4148.
This one you think it's fine?
http://www.digikey.com/product-detai...TTR-ND/1954014

[tibimakai]

Re: Sharp LC-40LE810UN question

The diode still shows OK.
The resistance between Vcc and Gnd is 122Kohm.

[budm]

Re: Sharp LC-40LE810UN question

That voltage supplied to D7910 and the transistor is used for other circuit. The positive leg of the start-up cap should be connected directly to the VCC pin of the SMPS IC.
I am tempted to use a 18V source to feed the VCC pin to kick start the SMPS IC and see if it will stay running after removing the kickstart. Do it with the protection lamp you made.

[tibimakai]

Re: Sharp LC-40LE810UN question

So basically just a touch with the 18V?
I don't understand what do you mean by:
"The positive leg of the start-up cap should be connected directly to the VCC pin of the SMPS IC."

[budm]

Re: Sharp LC-40LE810UN question

"The positive leg of the start-up cap should be connected directly to the VCC pin of the SMPS IC" I just want to verify if my drawing is correct that C7912 is hooked up as I traced it.

[tibimakai]

Re: Sharp LC-40LE810UN question

The pin#7 goes to R7929. It's on the right side of the IC.

[budm]

Re: Sharp LC-40LE810UN question

I see the trace goes under the IC body and then split? to the left and also to the right toward the start-up cap. Please look real close again.

[tibimakai]

Re: Sharp LC-40LE810UN question

It's not going directly to the cap, it's going through that transistor on the right side.
I have applied the 18V to pin#7, but nothing happened. The 109.5 at pin#5 (now it's lower 106V) became 126V.

[tom66]

Re: Sharp LC-40LE810UN question

Any output on the secondary when 18V applied?

[budm]

Re: Sharp LC-40LE810UN question

Well that connection does not make sense, if you look at the application notes I would think the connection will be real close to what you have. And since applying 18V directly still does not start up the circuits I am beginning to suspect the IC, but not 100% sure at this point.
Bed time for me now, night.

[tibimakai]

Re: Sharp LC-40LE810UN question

What exactly should I look for when I apply the 18V?
I was measuring the main caps and they remained at 162V.
Where I have marked with red that line shows 0.2Ohm.
On page #8 they mention some voltage has to be under 6.23V and I'm measuring 5.99-6.1V. Not sure what they mean by that though.
I'm suspecting the IC too and I can't seem to find it online, except from th Chinese dealers.

[tom66]

Re: Sharp LC-40LE810UN question

Output voltages. I think it's switching but it sees a short on the outputs. Check ALL of secondary for shorts. Do you have a scope yet?

[budm]

Re: Sharp LC-40LE810UN question

Any voltage on those two 2200uf 16V caps on the secondary side.