LG47LC7DF Fuse Blows

[vinceroger69]

Re: LG47LC7DF Fuse Blows

can you double check the numbers of that ic as no hits when looking on google for it

[budm]

Re: LG47LC7DF Fuse Blows

I need better straight shot pictures of the top and the bottom side of the board, right now I cannot really read the designators as printed on the board.

[killian6pk]

Re: LG47LC7DF Fuse Blows

I rechecked the numbers on the small chip. The first line reads 0001 the 1 is very faint but readable after cleaning the part, The second line does not have a small o like I thought that is the number one pin designator. The second line reads just H48. I can't find that number in google or on digikey.

I will get better pictures of both sides of the board.

[vinceroger69]

Re: LG47LC7DF Fuse Blows

http://www.semicon.sanken-ele.co.jp/...etail/SFA0001/

[killian6pk]

Re: LG47LC7DF Fuse Blows

Better pictures. Front and back

[killian6pk]

Re: LG47LC7DF Fuse Blows

I believe you found it. Thanks for hunting it down. Of course I am not smart enough to be able to understand any of that. Looks like it might be 6-16 volts in and 15 volts out. That is all I can tell. Will need help in getting specs to order if it proves to be bad after testing.

[killian6pk]

Re: LG47LC7DF Fuse Blows

I have checked on Digikey and Mouser under that SFA0001 part number and neither one has that number. Will email digikey with that pdf file attached and see if they can find a comparable part. I'll wait until we verify that I need it.

[vinceroger69]

Re: LG47LC7DF Fuse Blows

https://www.aliexpress.com/item/in-s...d22e04b87768-8
https://www.ebay.co.uk/itm/FAN7601-7...0yBX_zuOvkw6Cw

[budm]

Re: LG47LC7DF Fuse Blows

Q103 is not the PFC IC, that is the MOSFET for driving the power transformer for 12v and 24V? (I cannot read the connector Voltage labels).

[killian6pk]

Re: LG47LC7DF Fuse Blows

The picture of the back of the board shows a small IC labeled U301. That is the one that I think is the PFC IC.

Also picture of the cable voltages on the front of the board. Two pictures to make sure I got all three connectors where you could read them.

[budm]

Re: LG47LC7DF Fuse Blows

Circuit function blocks.
Pictures provided by shopjimmy.
LG EAY36781302 Power Supply / Backlight Inverter
http://www.shopjimmy.com/lg-eay36781...pply-unit.htm#
The SMPS IC that drives the shorted out MOSFET needs to be replaced.
You also need to to test ALL the component that are connected between the GATE of the MOSFET and the output drive pin of the SMPS IC.
The very low (<1 Ohm) OHMs resistor that is connected between Source and GND also needs to be checked including the Zener diode that is connected in parallel with the that very low Ohm resistor.

[killian6pk]

Re: LG47LC7DF Fuse Blows

On the InRush Current Limited (thermister) I can't get the actual part. It's specs are 6ohm 6amp 20%. I can get a 5ohm 6amp 25%. Would that work as a replacement.
Pulled a small Zener Diode from base of bad Mosfet. Readings are .670V and OL. I think that one is ok. Will keep looking for the other componets that Bud mentioned in post 31.

[killian6pk]

Re: LG47LC7DF Fuse Blows

Bud you asked me to check the components between the gate and the output drive pin of the smps IC attached is a link to that datasheet could you point out the output drive pin?

[killian6pk]

Re: LG47LC7DF Fuse Blows

How do you check surface mount resistors diode etc. Do they have to be removed from the board, or can they be read in circuit? Also I have a surface mount component with board identifier FB101, what does that stand for? It reads shorted with my dmm on continuity (both ways). There is no mention of it in the component list in the manual.

[tvtimmy]

Re: LG47LC7DF Fuse Blows

Fb101 is a ferite bead. It is a piece of wire enclosed in iron to reduce interference. It will always read short.

[vinceroger69]

Re: LG47LC7DF Fuse Blows

fb is probably a ferrite bead so should test short circuit surface mount parts unless i get a odd reading from the part i dont remove them but some diodes will read short circuit in circuit but there ok once removed.

[killian6pk]

Re: LG47LC7DF Fuse Blows

What about testing the surface mount resistors? Do I need to take them off the board?

[killian6pk]

Re: LG47LC7DF Fuse Blows

I have found a diode (black with blue strip) numbers are S3V79 (9 has a line under it and next to nine is a blue dot) can't find datasheet anywhere (internet search, digikey or mouser). On meter diode check setting reads both ways in circuit. Took it out of circuit it reads only one way with OL when leads are switched. Is it likely to be ok? Board designation is a D so not a Zener.

[killian6pk]

Re: LG47LC7DF Fuse Blows

I finally found a reference to this Diode. They say it is a Rectifier Diode, but still no data sheet. Don't know if that helps or not.

[vinceroger69]

Re: LG47LC7DF Fuse Blows

if the diode is only reading one way it should be fine