Panasonic tc-65cx420u No Power

[Jsikora]

Hello everyone,
I have this tc-65cx420u that I had to replace a couple of LED's on 1 row because the unit had the dark shadow down the center of the screen. Once those were replaced the unit worked just as before except the shadow was gone. Tried it several times to make sure everyting was going to work correctly beforere installing the panel as I did not want to take it back apart again. Replaced the panel and everything was working great. Picture was great and dark shadow was now gone. Checked several times and all was good. After reassembling the back cover on the screen I am now getting nothing what so ever. I do hear the PS noise that I had before, but have no standby light and hitting the power buttons on the TV or remote I am getting nothing. Any help with this would be greatly appreciated. Thanks.
Also I can post pictures and give voltage measurements once I get them wrote down.

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

Hopefully the panel wasn't damaged on reassembly, start here I guess to see where you stand: Test connector from mainboard to powerboard on powerboard side with all boards hooked up, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description/name and condition on and off.

[Jsikora]

Re: Panasonic tc-65cx420u No Power

OK here are pictures. I don't think there is an issue with the panel as I had the whole front frame back on after installing the panel and everything worked fine and I had picture on the screen and was able to get into the menu and even had it hooked up to watch TV.
So far I have checked con201 on the PS
starating from the top at 12V going down I have

12V = 12.81
12V = 12.80
DGND = -.005
DGND = -.004
DGND = -.004
5V = 5.16
5V = 5.16
5VSB = 5.17
PS/ON = 4.041
5V = 5.17
5V = 5.17
DGND = -.004
DGND = -.004

When the TV is plugged in I hear the PS and nothing changes when hitting the power button on the TV except the voltage on the main board that connects to the actual swith drops from 3.278 to .073 which in my experience should be right.

Thanks for your reply.

[budm]

Re: Panasonic tc-65cx420u No Power

OK here are pictures. I don't think there is an issue with the panel as I had the whole front frame back on after installing the panel and everything worked fine and I had picture on the screen and was able to get into the menu and even had it hooked up to watch TV.
So far I have checked con201 on the PS
starating from the top at 12V going down I have

12V = 12.81
12V = 12.80
DGND = -.005
DGND = -.004
DGND = -.004
5V = 5.16
5V = 5.16
5VSB = 5.17
PS/ON = 4.041
5V = 5.17
5V = 5.17
DGND = -.004
DGND = -.004

When the TV is plugged in I hear the PS and nothing changes when hitting the power button on the TV except the voltage on the main board that connects to the actual swith drops from 3.278 to .073 which in my experience should be right.

Thanks for your reply.

Those Voltage readings are fine, the PS-ON control signal from main board is present so the Switched 5V and switched 12V are.
We need to see the whole backside of the TV to see all the boards and how they are connected together.

[Jsikora]

Re: Panasonic tc-65cx420u No Power

Back Pictures

The other thing I can't figure out is no back lights or power indicator light which I had both of before the back was put on, even if the T-con is disconnected from the Panel.
Back lights all three sets test good at 121V with BL tester.

[budm]

Re: Panasonic tc-65cx420u No Power

So there are two more connectors from the power supply/LED driver board to the main board but the pins are not labeled (I do not see them), one of those two connectors should have BL-ON and Dimming control signals for the backlights.
The main board is not dead since the PS-ON is present, but does the PS-ON change state when you toggle the TV ON and OFF.
I assume that you already try re-seating all the cables, flexing the boards, tightened all the boards mounting screws?

[Grear]

Re: Panasonic tc-65cx420u No Power

Hello everyone,
I have this tc-65cx420u that I had to replace a couple of LED's on 1 row because the unit had the dark shadow down the center of the screen. Once those were replaced the unit worked just as before except the shadow was gone. Tried it several times to make sure everyting was going to work correctly beforere installing the panel as I did not want to take it back apart again. Replaced the panel and everything was working great. Picture was great and dark shadow was now gone. Checked several times and all was good. After reassembling the back cover on the screen I am now getting nothing what so ever. I do hear the PS noise that I had before, but have no standby light and hitting the power buttons on the TV or remote I am getting nothing. Any help with this would be greatly appreciated. Thanks.
Also I can post pictures and give voltage measurements once I get them wrote down.

Hello, I also have this same TV with the dark banding in the middle of the screen. Can you please tell me where you purchased the led strips and part number? I have replaced the driver board and this did not resolve the issue.

Thanks for any help, Grear.

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

Can you show a picture of the display fault?

[Grear]

Re: Panasonic tc-65cx420u No Power

Currently I don't have it connected to any satellite signal. The fault is a dark vertical shadow in the middle of the display that covers approx 1/3 of the screen.
An image of whatever is on can be seen through it.

[Grear]

Re: Panasonic tc-65cx420u No Power

Can you show a picture of the display fault?

Ok I found one, sorry for the content

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

Ok, that looks more like a tab bond fault than a backlight issue, hard to tell tho, without testing backlights, that's where the backlight testers come in handy. Half that content is good for America, not saying which, because I don't have enough time left to waste arguing the point.

[Grear]

Re: Panasonic tc-65cx420u No Power

Thanks for the reply, what would be the fix for a tab bond fault?

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

Example there, it's not a certified fix but I've had pretty good luck with it, some tvs are harder to get to the tab bonds, did one recently, used a piece of rubbber-like thermal pad for the shim, only did the top right and only did one side but his method is probably better: https://www.youtube.com/watch?v=purk_SyiT44

[Grear]

Re: Panasonic tc-65cx420u No Power

Thanks for the information, I'll definitely look into this.

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

Sometimes the symptoms can be deceiving, some present like he has, mine was just a dark area in the middle of the screen, no flickering.

[Jsikora]

Re: Panasonic tc-65cx420u No Power

So there are two more connectors from the power supply/LED driver board to the main board but the pins are not labeled (I do not see them), one of those two connectors should have BL-ON and Dimming control signals for the backlights.
The main board is not dead since the PS-ON is present, but does the PS-ON change state when you toggle the TV ON and OFF.
I assume that you already try re-seating all the cables, flexing the boards, tightened all the boards mounting screws?

OK, so I am going to give this a try once again. The last time I was doing anything with this, before the thread got hi-jacked, I lost patience. So anyway on those two 4-pin cables I am gettin voltages of

CN202
pin1 24.88
pin2 24.88
pin3 0.00
pin4 0.00

cn203
pin1 0.001
pin2 0.001
pin3 0.130
pin4 0.039

Not sure if that helps any or not but I'm willing to try and get this thing going again.

[Jsikora]

Re: Panasonic tc-65cx420u No Power

.

[nomoresonys]

Re: Panasonic tc-65cx420u No Power

More like he posted on an abandoned thread rather than a hijack, a year and a half since last post.

[Davi.p]

Re: Panasonic tc-65cx420u No Power

The only sensed thing one tech can do here is took hook a pc through serial port and check the log, Cultraview, the manufacturer of main board, use the serial over vga port, need an RT809 or another adapter..

[Jsikora]

Re: Panasonic tc-65cx420u No Power

Yeah I didn't realize it had been so long. Had a lot going on during that time. (Meds got changed several times and lost all realization of time frames.) I would like to get this working though, but right now I'm waiting on the IR/Power cable to get here from compass. Seems the end was ripped off since I was last working on this. I may just solder the wires to the board and see what I get. Didn't mean to sound like a jerk , just wasn't aware it had been so long.