LG 60PB5600 Sound but no Picture

[subwagon]

I was given an LG 60PB5600 after the original owner said they didn't want to spend 145 for a replacement board.

The tv powers on and has static I can tune to Ch3 and play a movie on the VCR of which I can hear but not see.

When the TV turns on it lights up gray for about 3 seconds then goes black and the sound turns on.

Upon opening the TV I found the HDMI port was broken off then someone tried to glue it on successfully shorting many of the pins. Despite this, the original owner said they were able to use the composite input to watch tv still prior to it going black.

In an attempt to see if it was worth fixing I Jumped the pins near R651 and R652 to initiate a test sequence with no luck i additionally jumped RL_on to 5.2v on the P/S with the same result (nothing but black screen).

The green light on the CTRL board is flashing short, short, short, Long. If i jump the board and remove ribbon cable to main board it gives flash:Long short, long,short

Thanks for your help in advance

[Hamie]

Re: LG 60PB5600 Sound but no Picture

The fact the screen lights up then goes off would suggest that y-sustain is probably working but you can check and see if -VY matches the label on start up.

Id say that you probably have a short on your buffer if I was to take a guess.

Check and see if any of the smd caps are shorted close to where the buffers join together.

[Nick's Tvs]

Re: LG 60PB5600 Sound but no Picture

Both the Y-sustain and the buffer boards commonly fail in this set they absolutely should be your first place the check.
Check out this video on how to check your buffer board IC chips for shorts.
Skip to minute 1 and listen through until minute 3.
Your buffer boards should be able to be tested the same way to confirm if your buffers are good or not
https://www.youtube.com/watch?v=AUEyXrXGAFo

[subwagon]

Re: LG 60PB5600 Sound but no Picture

Ok So here are some updates:

Build date 2013
All points checked with set on unless specified, listed by board label - voltage


VS 205V Actual->204.9
VA 55V Actual ->54.8

X-Sys Board:

Port P131.................
VS-204.9
VS-204.9
NC-0
GND-0
GND-0
+VA-54.8
+5V-5.2

Port P132.................
+VS- 204.9
+VS- 204.9
NC-0
GND-0
+5v - 5.2
+18V-17.9


Y-Sys Board:
Port P130.................
Vs-204.9
VS-204.9
NC-0
GND-0
5V-5.1
18V-17.9


Main Power Board:
M_On-3.0
RL_on-3.1
5.2V-5.2
GND-0
GND-0
5.2V-5.2
5.2V-5.2
GND-0
17V-16.8

Auto_GND-0
AC_on-5.1
17V_Det-2.6-0 when off
VS_-3.0-0 when off
GND-0
VS_DET-2.6
5.2V-5.2
GND-0
17V-16.8

Have not removed Buffer board yet for testing

[Hamie]

Re: LG 60PB5600 Sound but no Picture

You've not given -VY
Pictures would help.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

You've not given -VY
Pictures would help.

Whereabouts is -Vy, i have a sticker for VS and VA and associated test points on my p/s.

What pictures would you like, this model shared all but the input main board with its equally sized siblings in the 60PB family save for the 60PB6900.

[Hamie]

Re: LG 60PB5600 Sound but no Picture

Upload a picture of the y-sustain and buffers.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

You've not given -VY
Pictures would help.

I see Vy test points, but not sure if i can get a accurate reading now that i pulled the lower buffer board due to an exploded component at C975

I attached 2 pictures of the Buffer board 1 of the missing component and 1 of the service tag identification.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

Upload a picture of the y-sustain and buffers.

Here are Close up photos of the Upper Buffer ((2))

And photos of the Y-Sus board ((4))

[Hamie]

Re: LG 60PB5600 Sound but no Picture

If you're lucky replacing the cap should bring it back.
They are 4nf from memory.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

If you're lucky replacing the cap should bring it back.
They are 4nf from memory.

OK i put in 2 2000pf in parallel at C975, with no change still get the prime then nothing.

With the lower buffer removed the screen is gray on the top with just a hint of color on for about 3 seconds then back to black.


Va measured at 187.2V with both buffers back in

[subwagon]

Re: LG 60PB5600 Sound but no Picture

On y-Sus Board
I also removed R206 and R559 from circuit, they should read 2.2 ohms 5% but I measure 2.4 and 3.6 ohms. Ill have to go grab my notebook to remember how to test some of these other components like Q507,Q552, and Q553.

Any other components I should be particularly interested in?

[subwagon]

Re: LG 60PB5600 Sound but no Picture

Vy measured at 187.2V with both buffers back in

Said va meant vy

[Andrew F. Ali]

Re: LG 60PB5600 Sound but no Picture

I don't think Va means -VY. Usually Va=55V found on the PSU and Vy=-155V found on the Y-sus Bd. Thase are approximate values and not actual values for your Bd.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

I don't think Va means -VY. Usually Va=55V found on the PSU and Vy=-155V found on the Y-sus Bd. Thase are approximate values and not actual values for your Bd.

Right, I saw my mis-type after the edit period.

VA 55V Actual ->54.8 @ P/S
VY measured at 187.2V @ Y-SUS

[Hamie]

Re: LG 60PB5600 Sound but no Picture

As mentioned already the fact the screen lights up then goes off would suggest the y-sustain works.

Change the cap on the buffer and see if the tv works again.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

As mentioned already the fact the screen lights up then goes off would suggest the y-sustain works.

Change the cap on the buffer and see if the tv works again.

Unfortunately it didn't work. Replaced the blown cap with 2 2000pf caps in parallel for a total of 4000pf or 4nf. (mentioned above a few comments back).

So what should I try next?

After replacing the cap, I also tried running auto test on the logic board again with no response.

[subwagon]

Re: LG 60PB5600 Sound but no Picture

Any further advice or do i have a nice boat anchor?

[tom66]

Re: LG 60PB5600 Sound but no Picture

Did the Vsc voltage get checked?
If that is OK I would look at control board. Have you run test patterns?

[subwagon]

Dug this set up again to have a second look, this time I picked up a complete board set from shopjimmy and installed it. The set powers on then immediately powers off. If i disconnect the Y-sus boards P132 power cable the set will come on and stay on, and i can hear my input device. But no picture

Edit: Grabbed up a complete Y-SUS and buffer boards from the spare parts box and the set powers on / stays on with these new Y-Sus and buffer boards installed/ connected, But still no picture.

End result tv poweres on, screen stays black and no longer turns grey briefly. Set stays on but sound only.