LG 42LG50FD-AD Intermittent NoGo

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

Alright I have done what you recommended.
I am getting life from the VCC line.
VCC 13.74v

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

Right now I cannot tell the P/N or the designator of the PFC IC using that diagram, way too small to read the P/N.
We need spec sheet.

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

BTW, PFC diode D601 resistance test is OK off the board?

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

I might try get some good photos any idea on how many pins this chip has.

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

I might try get some good photos any idea on how many pins this chip has.

The schematic you have shows 8 pin, why do ask? Are you sure you are looking at the right IC the schematic actually matches your board?
So far you did not provide good clear straight shot pictures of the whole top and bottom side of YOUR power supply board.

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

Diode 601 checked out fine.

Working on getting a photo of board.

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

Diode 601 checked out fine.

Working on getting a photo of board.

What resistance reading do you get when reading both ways?
Was it tested off the board or in circuit?

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

BTW, I look at the picture of the power supply board provided by OP in post #, that power supply board uses two PFC Voltage booster circuits (you can see that it has two PFC Inductors), the schematic only shows one PFC circuit.

Based on P/N you provided earlier, your board also has two PFC circuit, so the schematic does not match the board.
http://www.shopjimmy.com/lg-eay40505...upply-unit.htm
LG EAY40505203 (EAX40157601/17) Power Supply Unit

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

here are some photos I tried very hard to get the components lettering and numbers in the shot clear.
Hope they will help us here.

[vinceroger69]

Re: LG 42LG50FD-AD Intermittent NoGo

there is a small 8 pin ic on the bottom of the primary side of the psu can you read the part number from it so we can find a data sheet for it

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

that 8pin chip reads.
1207A
PACD

[vinceroger69]

Re: LG 42LG50FD-AD Intermittent NoGo

sorry forgot to ask whats the part numbers of the two 16 leg ics

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

middle 16 leg ic
NCP1396AG
PAB905

end 16 leg ic
8CADROM
UCC28060 G4

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

so I probably should check all VCC lines?
I noticed each of these chips has a VCC line.

[Amraks]

What resistance reading do you get when reading both ways?
Was it tested off the board or in circuit?

D601 was tested out of circuit.
21.19k one way. (+ ->| -)
0.L the other. (- ->| +)

Is that fine

[budm]

Re: LG 42LG50FD-AD Intermittent NoGo

https://cdn.badcaps-static.com/pdfs/...954aecb1b0.pdf

https://cdn.badcaps-static.com/pdfs/...823318728e.pdf

So the schematic does not match the board..
So D601 may not be what I think it is until the connections are traced out to find its function.

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

So I metered the VCC on UCC28060 G4 which is the PFC chip we was looking for

Its 14.62v so there is power there.
Where do I go from here.

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

Just thought I would show the orientation of the chip and draw out the VCC line a little bit.

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

PWMCNTL how would I go about checking voltage on this line?
Would do the same as I did for the VCC line.
Main Filter Cap Negative to Negative lead and Positive lead to PWMCNTL pin?
It would be interesting to see if this gets enabled and shuts down the chip.

[Amraks]

Re: LG 42LG50FD-AD Intermittent NoGo

I traced that d601 it goes through some smd resistors and a smd cap to pin 1(ZCDB) on UCC28060.