Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting TVs and Video Sources
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 01-23-2019, 01:57 PM   #1
zacheriaj
Senior Member
 
Join Date: Jan 2014
City & State: Madison, WI
My Country: United States
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 115
Default RCA LED65G55R120Q No Backlight

hello, I picked this TV up for free and started to diagnose it. I assume either a main board issue or shorted LED's. When I power it on, my voltages come up correctly and the LED's light for a split second. Then the entire system shuts down. No voltage anywhere. I assume shorted LED's forcing the PSU into protect so I disconnected the LED connector, powered on again, and the same issue occurred. Voltages came up for a second and then everything shut down. Any ideas?
__________________
You Can't Succeed Until You're Willing to Fail
zacheriaj is offline   Reply With Quote
Old 01-23-2019, 02:23 PM   #2
nomoresonys
Badcaps Veteran
 
Join Date: Jan 2013
City & State: midwest
My Country: U.S.
I'm a: Knowledge Seeker
Posts: 2,703
Default Re: RCA LED65G55R120Q No Backlight

Try disconnect powerboard from mainboard, turn it on see if backlight come on and stay on, always good practice to have tv unplugged from wall outlet before unplug any connector then plug tv in and try.
nomoresonys is online now   Reply With Quote
Old 01-23-2019, 03:19 PM   #3
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,680
Default Re: RCA LED65G55R120Q No Backlight

Pictures of what we are dealing with will help.
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
budm is online now   Reply With Quote
Old 01-23-2019, 04:03 PM   #4
zacheriaj
Senior Member
 
Join Date: Jan 2014
City & State: Madison, WI
My Country: United States
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 115
Default Re: RCA LED65G55R120Q No Backlight

Quote:
Originally Posted by budm View Post
Pictures of what we are dealing with will help.
What connection should I remove on the main board?
Attached Images
File Type: jpg 0123191559a.jpg (842.7 KB, 11 views)
File Type: jpg 0123191559c.jpg (770.9 KB, 8 views)
zacheriaj is offline   Reply With Quote
Old 01-23-2019, 11:29 PM   #5
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,680
Default Re: RCA LED65G55R120Q No Backlight

"When I power it on, my voltages come up correctly and the LED's light for a split second."
So what DC Voltages do you have on the control pins of the power supply board connector CN2: ADJ, BK, and PS?
What Voltages do you have on the LED connector pins with LED connector in place? You need to leave the probe on each pin and then Turn on the TV to see how high it goes up to then wait 5 seconds to see how low it goes down to, do that on each pin of the LED connector, black probe on the chassis GND, you have two LED (+) and two LED (-) so 4 tests total.

Last edited by budm; 01-23-2019 at 11:34 PM..
budm is online now   Reply With Quote
Old 01-24-2019, 09:30 PM   #6
maxvalutech
Badcaps Veteran
 
Join Date: Dec 2014
City & State: forster nsw
My Country: australia
Line Voltage: 240v
I'm a: Knowledge Seeker
Posts: 715
Default Re: RCA LED65G55R120Q No Backlight

Voltage checks are a must as budm has indicated. A year ago I had set from friend of friend with similar problem except logo displayed. Power board and LEDs checked out OK by forcing them on. That left me with likely eeprom corrupted on main board. That set 65" Polaroid similar to RCA was recently given to me and I will first be trying freeze spray on the eeprom.
maxvalutech is offline   Reply With Quote
Old 01-30-2019, 04:58 PM   #7
zacheriaj
Senior Member
 
Join Date: Jan 2014
City & State: Madison, WI
My Country: United States
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 115
Default Re: RCA LED65G55R120Q No Backlight

Quote:
Originally Posted by budm View Post
"When I power it on, my voltages come up correctly and the LED's light for a split second."
So what DC Voltages do you have on the control pins of the power supply board connector CN2: ADJ, BK, and PS?
What Voltages do you have on the LED connector pins with LED connector in place? You need to leave the probe on each pin and then Turn on the TV to see how high it goes up to then wait 5 seconds to see how low it goes down to, do that on each pin of the LED connector, black probe on the chassis GND, you have two LED (+) and two LED (-) so 4 tests total.
Sorry for the delay. I'm in WI and its been a rough week! Finally got voltages for you.

PS-5Vs: 5.1v always

ADJ-BK: 1.6v when turned on, drops to 0

5V+5V: 4.9v once powered on, then drops to 0

LED Connector (left to right)
+: 285V drops to 0 in five seconds
-: no reading

+: 135V drops to 0 in 5 seconds
-: no reading

Last edited by zacheriaj; 01-30-2019 at 04:59 PM..
zacheriaj is offline   Reply With Quote
Old 01-31-2019, 12:19 PM   #8
Andrew F. Ali
Badcaps Veteran
 
Andrew F. Ali's Avatar
 
Join Date: Jan 2014
City & State: Point Fortin
My Country: Trinidad & Tobago
Line Voltage: 125VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,352
Default Re: RCA LED65G55R120Q No Backlight

This is the typical Backlight failure issue.
Andrew F. Ali is offline   Reply With Quote
Old 01-31-2019, 01:32 PM   #9
zacheriaj
Senior Member
 
Join Date: Jan 2014
City & State: Madison, WI
My Country: United States
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 115
Default Re: RCA LED65G55R120Q No Backlight

Quote:
Originally Posted by Andrew F. Ali View Post
This is the typical Backlight failure issue.
I assume the low voltage string is bad?
zacheriaj is offline   Reply With Quote
Old 01-31-2019, 02:07 PM   #10
Andrew F. Ali
Badcaps Veteran
 
Andrew F. Ali's Avatar
 
Join Date: Jan 2014
City & State: Point Fortin
My Country: Trinidad & Tobago
Line Voltage: 125VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,352
Default Re: RCA LED65G55R120Q No Backlight

The higher voltage string is showing the same symptom. By displaying 0V on the both (-) pins say the Backlights are faulty and if you want to fix it then you would have to open up the Panel and test the Backlight Strings.
Andrew F. Ali is offline   Reply With Quote
Old 01-31-2019, 03:14 PM   #11
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,680
Default Re: RCA LED65G55R120Q No Backlight

Quote:
Originally Posted by zacheriaj View Post
Sorry for the delay. I'm in WI and its been a rough week! Finally got voltages for you.

PS-5Vs: 5.1v always

ADJ-BK: 1.6v when turned on, drops to 0

5V+5V: 4.9v once powered on, then drops to 0

LED Connector (left to right)
+: 285V drops to 0 in five seconds
-: no reading

+: 135V drops to 0 in 5 seconds
-: no reading
You count the pins wrong for the connector CN2. It has 18 pins total. The expose pins you see from the top side of the board are ODD number pins, the even number pin you will have probe from the bottom side of the board or via the wire entrance side of the connector.
Pin name assignment for example: Pin 17 is ADJ (DIM control), Pin 18 is BK (BL-ON).
1) So to troubleshoot the problem we will need correct data first.
2) I need the pictures of the bottom side of the power supply board to see if the two LED strings are connected in series or not.
This looks to be the same as your board:
https://www.shopjimmy.com/rca-re46hq...led-board.htm#
RCA RE46HQ2120 Power Supply / LED Board
budm is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 04:56 PM.
Did you find this forum helpful?