Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

[gavric]

Hello Everyone, I been reader here for quite a wwhile and managed to fix several tvs with suggestions from here. This time I am stumped. I am working on Westinghouse DWM55F1G1 that has sound and backlight but blank screen. Upon taking it apart I measured voltage going into tcon and 12V was missing. I looked down tcon cable toward main/power supply board and noticed that little three legged small part(diode???) is burned and bubbled right next to tcon cable connector. I barely touched and it all crumbled. I had similar case where same thing happened with same tv brand and after jumping 12V onto tcon fuse picture came on and tv worked. Replacement main solved that previous problem.

This time I ordered replacement main/power supply and after everything was in place tv would only cycle and not come up. If I unplug tcon cable tv would start up and stay ON. This tv model does not have tcon board that is removable, it is integrated into screen strip and something there is shorted and shuts main board down. Short is on main strip where all big ICs are because when I disconnect ribbon going into other half of screen it still shorts out. I read about possibly tiny capacitor being shorted but there is quite a lot of them. I tested all little caps brown and black for shorts like this, with multimeter in diode mode and found none that are dead shorted across. They all beep same in diode mode- for millisecond and stop beeping. I would like you guys to direct me into which of them I would take off and see if it resolves short. I have capacitor tester also but i only tested tiny caps for dead shorts across in diode mode without removing. When in diode mode between tv chassis(grnd) and tcon fuse I get .160 . See last picture.

[martino]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

Do you have a variable power supply?
I'd feed the 12vdc in with lets say 5 volts while having the board frozen(can of air upside down) and see what component melts the frosting the fastest.it reveals the shorted component or pinpoint the problem area pretty fast.

[gavric]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

Do you have a variable power supply?
I'd feed the 12vdc in with lets say 5 volts while having the board frozen(can of air upside down) and see what component melts the frosting the fastest.it reveals the shorted component or pinpoint the problem area pretty fast.

Thanks for suggestion, I did try connecting external 12v , ground to tv chassis and 12v+ to tcons fuse and fuse blew immediately, if i put 12+after fuse my external power supply shorts out- red led on it starts winking at me, telling me to stop it. i did try to feed 12v for few seconds and touch big IC chips but did not feel any that are getting warm or hot. I did watch youtube video where guy found shorted capacitor on one of these built in tcons but he never said if he got it by luck or somehow tested it while it was still on the board. he said it tested shorted but did not say how he did it. these capacitors are soo small that I am sure that i will mess up if I start taking them off one by one.

[martino]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

The idea with a lower voltage is that things don't explode in your face,it's about applying just enough voltage with preferably low current to expose the shorted or stressed component by it getting warmer quicker then the rest.
I often even start at 3 volts and slowly work my way up till I get to see a suspect.
And you need to freeze the board first,upside down can of air will freeze it in a few seconds for you.
Let me find an example....watch this video.
https://www.youtube.com/watch?v=O7X_E9nq27k

[gavric]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

The idea with a lower voltage is that things don't explode in your face,it's about applying just enough voltage with preferably low current to expose the shorted or stressed component by it getting warmer quicker then the rest.
I often even start at 3 volts and slowly work my way up till I get to see a suspect.
And you need to freeze the board first,upside down can of air will freeze it in a few seconds for you.
Let me find an example....watch this video.
https://www.youtube.com/watch?v=O7X_E9nq27k

OK I will give it a try with the spray because I just seen how little difference in time to unfreeze is between shorted and good parts. Thanks for your reply.

[gavric]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

I did testing with freezing the board with spray and one part capacitor did unfreeze little faster than rest of frozen board. i tried it several times and it it did it every time. i took it off and short is now gone in built-in tcon but no picture because this little part is out of the board and i am not sure what value this little value is. My ESR meter dont read it at all. multimeter diode mode gives me constant been either way. i would like to know how to figure out what capacitor to put into its place, maybe i should unsloder one next to it and measure it if i can?

[budm]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

It is connected in parallel with the other caps next to it, so remove one of them and check the capacitance. More likely it is part of the filter caps for VCC.
You can also check the DCV between the two pads of the cap to figure out what the cap Voltage should be.

[gavric]

Re: Default Westinghouse DWM55F1G1 Shorted tcon, tcon built into screen

It is connected in parallel with the other caps next to it, so remove one of them and check the capacitance. More likely it is part of the filter caps for VCC.
You can also check the DCV between the two pads of the cap to figure out what the cap Voltage should be.

Thanks for your quick reply. I did remove little cap right next to it and I did see that they are connected in parallel and voltage across measured at 12V. I measured good cap at 10uF and replaced it with regular small 10uF 50v cap but no joy, no image displayed. I officially just gave up on this tv because I spent way too many hours on it and probably this built-in tcon is toasted because of initial damage to it where main board burned up because of this shorted capacitor on built-in tcon -where tcon fuse did not blow open before damage was done to main board. Main board had severely burned spot (where it feeds power to tcon cable) where it actually burned the green board but tiny tcon fuse did not blow.
At least I learned cool way how to hunt down shorted components.
I wish to THANK all of you for your suggestions and I hope to talk to you really soon.