LG 60PB5600 Sound but no Picture

[subwagon]

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?

what pins do i need to short out to start the test pattern test ?

[subwagon]

Tried a different set of buffer boards and got sparks on the lower buffer board C975. These boards came from shopjimmy and were supposed to be tested good.
Any suggestions, thanks in advance.

[subwagon]

Went back to the first buffer boards and Y-SUS, tested all voltages came back with.

VS - 54V (expected 55V)
VA - 204.5~204.7 (expected 205V)
5V - 5.1V
18v - 3.4V

So it looks like im not getting my 18V. I isolated the Y-Sus board and still only see 3.4V at the Z-Sus board's 18V pin.
Swapped the Z-Sus board with another Zboard from shop Jummy and still get all the same voltage measurements.

Am I correct to assume that the 18v is produced at the Z board and passed on to the Y board?

[nomoresonys]

Make sure the buffer boards are not shorted, test video: https://www.youtube.com/watch?v=3Oq2MsU0XOQ

[nomoresonys]

Probably make sure that replacement for c975 is the correct cap, prolly don't try using two caps like that, if buffers check out ok, that is no shorts on any IC or none of the other caps, more than likely will be a bad cap on the y-sus board. Important to remember that a bad buffer will take out a good y-sus and vise versa.

[subwagon]

Make sure the buffer boards are not shorted, test video: https://www.youtube.com/watch?v=3Oq2MsU0XOQ

Raked both sets of buffer boards and found no shorted pins.

[subwagon]

Here's what I have so far:

Ill split them into 3 sets, as this is how i have been testing them:

Set A -From shopjimmy
with this set installed Y board and buffer boards the set will turn off in a few seconds after powering up. I suspect the Y board to be damaged. First time i plugged this complete set in I saw sparks coming from the lower buffer C975 cap. Buffers raked no shorts found.

Set B - Purchased as spare parts from Ebay. Y board and buffer boards.
TV Set powers on and stays on but no picture and no 18v, get ~3.7 V instead, the rest of the Listed voltages measure in tolerance. Buffers raked, no shorts found.

Set C- the original set with blown C975 cap- Unused and in a box, attempted repair but never got any where with these.-Currently lost cant seem to locate them right now.


Now a few questions:

• Is there a good way to test the Y-SUS board independently?
• Can I run a single buffer board off the Y-Sus or will it damage somthing else?
• Is it possible my screen could be damaged and is blowing up my boards? Is there a way to test the screen?

Thanks again everyone.

[nomoresonys]

Should be ok to powerup with just the top buffer in, probably get a half screen glow if working right. Since you have more buffers to compare, check all the caps in ohm mode, also check C975 and C977, C978 if present see if there's any big differences or shorted caps, meaning compare one lower buffer to the other lower buffer. What do you get when you compare C975 on each buffer board?

[nomoresonys]

Important to make sure all screws are in place and tight when testing or running tv, one loose screw can short out a board rather easily, specially on plasmas.

[nomoresonys]

Be sure to check C873, C869, C867.

[subwagon]

Be sure to check C873, C869, C867.

Is there any special way I should be checking these with a meter? in ohm mode none of the capacitors are shorted across. Removed both buffer boards from set to test. Same results with both sets of boards no shorts.

[subwagon]

Thanks everyone for your help, recycling the set and moving on to an new project.