LG 42PC5D Plasma no pic but sound

[maddog310]

Hi, have another one here to attempt to fix.
Did the light bulb trick, no light with boards connected or disconnected.
Three green leds on control board lit, i believe there are four, and one on main board.
Two 450v 270uf Nichicon caps look slightly bulged.

Took some voltage readings at the connectors. VS :190v, VA :60v on the sticker.

P11 to xmain

VS : 189.8v
VS : 189.8v
NC :
GND :
GND :
VA : 59.3v
GND :
5V :4.98v

P12 to y board

VS : 189.8v
VS : 189.8v
NC :
GND :
GND :
GND :
VA : 59.3v
GND :
5V : 4.99v

P3 to main board

3.4v : 3.421v
3.4v : 3.421v
GND :
GND :
6v : 6v
6v : 6v
GND :
GND :
12V : 12.09v
12v : 12.09v
GND :
GND :

P2 to main board

19v : 19.05v
19v : 19.05v
GND :
GND :
6v : 6v
GND :
3.4V : 3.422V
GND :
12v : 12.09v
GND :

P1 to main board

AC DET : 4.85v
RL ON : 5.06v
STB5V : 5.07v
GND :
VS ON : 5.03v
5V DET : 4.47V
M5V ON : 5.06v
STB5V : 5.06v
GND :
NC :
6V : 6v
GND :
3.4V ON : 5.06V

P103 y main connector

+5V : 4.98v
GND :
+VA : 59.2v
GND :
GND :
GND :
NC :
+VS : 189.6v
+VS : 189.6v

P1 x main connector

+VS : 189.7v
+VS : 189.7v
NC :
GND :
GND :
VA : 59.2v
GND :
+5V : 4.95v

Anyone have any thoughts on these figures, pics to follow.
I have read it could possibly be a ipm on y board!

Any help is appreciated.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Here are a few pics.

[tom66]

Re: LG 42PC5D Plasma no pic but sound

On the top left of the Y-sus you have a bank of five red capacitors:
https://www.badcaps.net/forum/attach...5&d=1365742983

Check the voltage across any of these (they are in parallel.) What do you measure?

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Tom66, it seems to fluctuate between 98.5v and 95.5v approximately.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

So i took the Y and Z boards out and checked the IPM's, they appear to be bad by the values i measured.

Tested in diode mode.

Ysus
Forward
Test 1: GND + SUS OUT - = .345v
2: SUS OUT + VS - = .341v

Diode value over 0.4v = OK

Reverse
Test 1: GND - SUS OUT + = OL
2: SUS OUT - VS + = OL

Diode value is infinity = OK

Zsus
Forward
Test 1: GND + SUS OUT - = .346v
2: SUS OUT + VS - = .347v

Diode value over 0.4v = OK

Reverse
Test 1: GND - SUS OUT + = OL
2: SUS OUT - VS + = OL

Diode value is infinity = OK

Here are the pages i found for testing.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

On the control board there are four Temp Diodes, D1, D2, D3, and D4.
Three of them are lit and D1 is not.
Does any one know if this is connected with these IPM's?

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Pic of diodes on control board are on page 57 of this manual.
Would have uploaded only that page but wasn't able to.

[tom66]

Re: LG 42PC5D Plasma no pic but sound

The LEDs are good. All lit is bad. Otherwise is OK.

I have had bad IPM which tested good on meter (diode test) but was dead anyway. Sometimes it would make a ticking/clicking sound.

You need to compare the voltage on the Y-sus caps to the same on the Z-sus' five red caps.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps.

If i were to change the ipm's, what should i be checking before installing them, so they don't get fried!
Where could i get these, part # AEF31675201(A), 0651SANY(P).

[hienton2]

Re: LG 42PC5D Plasma no pic but sound

Maddog310.

My plasma problem is very much same as yours.
https://www.badcaps.net/forum/showthread.php?t=27960

Do you feel any warm on the ipm z sus and y sus.
Mine z sus ipm is very cold when tv running. Y sus is warm.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Hey hienton2, as i recall both were warm, check out these two treads.

https://www.badcaps.net/forum/showthread.php?t=14214

https://www.badcaps.net/forum/showthread.php?t=8920

Possibly it's blown also!

[tom66]

Re: LG 42PC5D Plasma no pic but sound

The bad ones on mine were warm too, I recall.
Which one is fluctuating? Are both fluctuating?

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps.

If i were to change the ipm's, what should i be checking before installing them, so they don't get fried!
Where could i get these, part # AEF31675201(A), 0651SANY(P).

I believe these voltages are good from what i have read, any where from 60v to 120v is good!

I think i have bad components on ysus, diodes and mosfets around the 15v section.

Details to follow.

[tom66]

Re: LG 42PC5D Plasma no pic but sound

Which voltage on the ERC caps was fluctuating?

60V to 120V is a general rule, if you have a good meter, measure the output on DC VRMS of the sustain board and across the caps, it should be nearly the same (+/-5%); that is the best test.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Which voltage on the ERC caps was fluctuating?

60V to 120V is a general rule, if you have a good meter, measure the output on DC VRMS of the sustain board and across the caps, it should be nearly the same (+/-5%); that is the best test.

Both voltages at the five red caps fluctuate.
Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps. Copied from previous post.

I checked diodes at D202, D203, D204, D205 plus others on ysus.
I get in diode mode.

D202 forward .434v reverse .790v
D203 forward .433v reverse .841v
D204 forward .446v reverse OL
D205 forward .443v reverse OL

So it looks like the first two are bad! Checked others on the board and they test like the last two.

Also checked Q1 and Q2 mosfets.

Q1 D to S 160.8 kohms
Q2 D to S OL

Looks like Q1 is bad! That heat sink was very hot also.

Is there anything else i should be checking? resistors?

The bad diode has F46J on it, I can't seem to find a replacement.
Pics of ysus.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Any thoughts on what I've posted!

[tom66]

Re: LG 42PC5D Plasma no pic but sound

Q1 G-S and G-D too.
D's need to be verified out of circuit as they may be OK.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Q1
D to S 160.8 kohms
G to S 5.2 kohms
G to D 235 kohms

Q2
D to S OL
G to S 37.66 kohms
G to D 7.44 Mohms

[tom66]

Re: LG 42PC5D Plasma no pic but sound

The G-S is very suspicious, so you will need to remove it (or disconnect two leads) and re-test the resistance.

[maddog310]

Re: LG 42PC5D Plasma no pic but sound

Ok, will do..... Q1.

What do you think of the values of these diodes also.
I checked diodes at D202, D203, D204, D205 plus others on ysus.
I get in diode mode.

D202 forward .434v reverse .790v
D203 forward .433v reverse .841v
D204 forward .446v reverse OL
D205 forward .443v reverse OL

So it looks like the first two are bad! Checked others on the board and they test like the last two.