Panasonic TC-55cx420 Backlight Control

[jason123]

Hi there, Just curious if anyone has ever seen a TV that doesn't have Backlight adjustment / Control?
I just picked up this TV that had one LED go bad on it. I replaced the LED and all is good. I went to the menu to lower the Backlight setting to preserve the life on the backlight LEDs and I can't seem to find a knob / control for backlight? There is Brightness - and that's all.
Thank you

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

I have a Panasonic TX-L47E5B and have never found any control to turn the backlight down either in the On Screen or Service Menu.
If anyone knows how I too would be interested in knowing.

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

See if this will work for you. Just found this on the net. However when I change the backlight and store it, it does not appear to make any difference to the backlight level?

Pages 15 & 16

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Thank you so much! Yes, this worked for me. Though all the menus are different, but I was able to adjust backlight and it's saved. Thanks again.

[budm]

Re: Panasonic TC-55cx420 Backlight Control

Based on that service manua page 25l, there is Dimming control line (BL_PWMA) that you may be able to set the backlights level without going into service mode. I wonder if the backlights level is also set by the 'Brightness' setting level on TV or not.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

You actually solved another problem I was having, dick_barton. The software is glitchy on this TV, it locks up and just not smooth. So I have been attempting to upgrade the firmware without success. Following their process, put code on Flash, unplug from wall, and it should start the process upon plugging in - never happened. Software upgrade was giving me errors within the menu too. I had to go into the service menu and set "Update Software" to Yes, and that got it to work. Thanks again. Still as glitchy as ever though. one of the worst I think?

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

Glad it was of some help. I must admit the Panasonic I have is excellent and the only downsides are no wireless network installed although I could buy a plugin. However I have it wired to the Ethernet input since my router is close by.
The sound is crap so I use a surround sound system with it.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Yes, I agree fully .. the sound is terrible. It turns out there is something wrong with my main card. I updated firmware, then I reset "everything" but still, it freezes, can't update software (every time I go to that screen and hit "Update" it says it can not check data" or something like that and it locks up .. I have to unplug from the wall), and menus simply disappear after I click on them (both button and remote).. So I'm thinking a new main board is needed?

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Ok, I've very new to Panasonic this is my first Panasonic TV.

I fixed the backlight issue and control seems to work through the service menu.

This TV seems to be very glitchy. Sometimes on power up, the "Volume" doesn't work. I have to unplug from wall and plug back again. At times menus just freeze. It plays network content (Netflix and others) fine.
One menu that always freezes everything is "Software Update." Seems that I have to unplug from the wall after the message "can not get information, please check network setting and try again!"

Finally, I ordered a main board from eBay thinking this is it. Seller swears it is a working main board. When I install - I only get backlight and on/off activity. Nothing at all on the screen - no logo or anything else. Does the main board have to match the LED control board (are they paired and need to be replaced together?) or did I just get a bad board? I installed my glitchy main board and it's fine

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

As far as I am aware it has to match your panel so that it's driving the correct Tcon board. Be interested in knowing what others think.

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

Can you post clear pictures of your boards to see the set up.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Can you post clear pictures of your boards to see the set up.

Here you go

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

I must admit I've not seen a set like this so wouldn't know where to start.
Have you looked to see if you could do a firmware update via USB?

I would wait for others to chip in who may have more experience with Panasonic.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Thanks.. yes, I have done Firmware update on it, but both images (installed and new) were the same revision, but it did as far as I could tell.

[dick_barton]

Re: Panasonic TC-55cx420 Backlight Control

A search of the board number CV6488H-A comes up as being used in a number of different sets. Could your supplier tell you which make of TV it came from.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

He had it listed as coming from a Panasonic TC-55cx420U which is exactly what I have. Labels on the 2 boards seem to be identical.

[nomoresonys]

Re: Panasonic TC-55cx420 Backlight Control

Did you try a factory reset to try to fix the glitches? will need to reset preferences after of course.

[jason123]

Re: Panasonic TC-55cx420 Backlight Control

Hi, yes, I did a factory reset both from the standard menu and from the service menu. Not much of a difference.

[nomoresonys]

Re: Panasonic TC-55cx420 Backlight Control

Eeprom could be messed up.

[madlee357]

Re: Panasonic TC-55cx420 Backlight Control

I have this set and its totally dead