Proscan 40LD45Q 40" LCD TV Help Needed!

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

So are those 2 caps the ballast caps? Here are some more pictures. I even got pictures of the color bleeding. Looks like I will be replacing the IC on the T-Con board. My previous attempts on other T-con boards failed but I have better equipment now.

That big cap on the board is just temporary until I get a replacement.

Also this T-Con board had magnets that it was screwed down with, never seen these before. I tried to remove them but then there was no way to screw down the T-Con board.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

OK, so I am having a problem testing these blue caps. I have 3 multimeters and I am getting nothing. I also tried to test some other blue caps but I still get nothing. So I guess I do not know how to test these. What is the proper way? Please & Thank you.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

I found this online.


http://www.electronicrepairguide.com...r-leakage.html
__________________________________________
So the right way to check the ceramic capacitor leakage is to use an insulation tester. If you have the analog insulation tester or meter, the meter panel will show a short circuit when certain voltage are applied to check the ceramic capacitor dielectrics or materials. The voltages that you can select is depends on the brand or model you had. Some have the range of 50v to 1000v and some have the range from 100v to 5000v. It is optional whether you should have one.
_______________________________

A insulation tester looks very expensive and this web site explains the exact problem I am having with the TV. So the main cause must be these 2 or one of the 2 blue ceramic caps. That is my guess.

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Looking at the bottom side of the board, it looks like the Inverter transformer high Voltage winding of the the two Inverter transformers are connected in parallel to drive the lamps, and those two high Voltage caps are used for the lamps sensing circuit.
Testing those cap with low Voltage does not give real indication of the leakage, the cap is exposed to 1000's of Volts in the circuit.
BTW, do you have the LCD panel model number?

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

I believe it is TH400HW01-V5 A and the brand is AUO

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

T400HW01-V5 A. I did not find the spec for the 'A'. I found V5 version 1 which uses the long Inverter board, not the same as your screen.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

I have a long inverter board on my panel.

Is an insulation tester the only way to test these high voltage ceramic caps?

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Your TV uses power supply/Inverter combo board, that long board attached to the lamps is Balancer board, it is used so all the lamps will evenly conduct.
This why it is important to see the whole backside of the TV so we can see all the boards and how they are connected together.
That small connector on the Blalancer board, can you get close up picture so we can see the pin labels. An where does that cable go to on the other end?

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Here are some better pictures. I am about to close it up until I get parts in.

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

So what DCV do you have on that small connector on the Balancer board?
LD = ??? VDC
VCC = ???? VDC

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Ld = 6.21 vdc
vcc = 12.02 vdc

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Ld = 6.21 vdc
vcc = 12.02 vdc

You have LAMP problem or bad balancer transformer/s.
Normal condition when ALL the lamps are on and conducting, the LD (Lamp Detector) will be >11VDC, if one lamp or more does not stay conduct, it will cause an imbalance so the LD signal will go <10V indicating error.
Since you disconnected the cap, then there is no protection circuit any more, those two caps are not used as ballast caps in this case.
I would look at the TV screen that show all white image on the screen so you can see if one of the lamp is on or not, you will see dark bar on the screen if you look really well, you may try lowing down the backlights level to see if you can see it better.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Backlights are good. Most of the transformers have an OHM reading of 312 but but some are 308 and 1 is 304 ohms.

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Well that does not make sense then that the LD error signal is that low, it may be the error detection itself is bad.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Everywhere I read online it says capacitors cause the problem with the backlights turning on for 2 seconds and turning off. That is why I removed the 2 blue ceramic caps.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

There is an IC 2903. I looked it up and tested it, seems to be good. "LOW POWER DUAL VOLTAGE COMPARATOR" All the diodes on the inverter board test good.

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

The LD signal is generated by the comparator IC. Detect the output of those little transformer on the Balancer board.
For examples:
https://www.youtube.com/watch?v=oE6K4xBVweA
https://www.youtube.com/watch?v=8oZnSleucJ0

The Balancer system used a lot in SONY and SAMSUNG TVs.

[dick_barton]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

Pehaps the capacitors you have removed are in part of the lamp error detection circuit and feedback any problem with the lamps to the controlling IC which now thinks there is a lamp error and is indicating a fault.
If you cannot test the caps then it would be easier to replace them.

[budm]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

I would try replacing those two high Voltage caps since you do not real tool to simulate a couple thousand Volt to apply to the cap to find out if the caps are good or not for sure.
You can also try putting the caps back in place and then removing the LD signal wire from the inverter board and then use 1K between the 12V and the LD wire to fool the circuit and see if the Backlights will stay on.

[Shane711]

Re: Proscan 40LD45Q 40" LCD TV Help Needed!

OK, so I watched the videos and I did all the testing. Reconnected the 2 blue caps. Tested the outputs on all the transformers and they all were about the same, 0.350 VAC. I even disconnected all the backlights and only had 1 connected at a time, I power cycled it each time and all the lights lit. Looks like the inverter board and the CFLs all test good.

When I have the 2 blue caps disconnected and the TV on, after a minute or so all the outputs on the inverter transformers drop down to 0.002 VAC

Is 0.350 to high of an output? All the CFLs look good, no burn marks on the ends.

I did notice I have a bad ribbon cable from the T-Con board to the Panel. I will replace that to see if it fixes the color bleeding. I ordered some RM5101 & AS15-F ICs just in case. I still have that Vizio with a bad AS15-F that I have not fixed.

And I ordered some 5PF 6KV Ceramic Caps.

Coppell TV Repair has a kit to fix this problem. I contacted them and they said the kit only contains caps but they didn't tell me which ones. Could be ceramic or even poly.
( http://www.coppelltvrepair.com/p/634...ng-off-problem )