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Old 05-23-2022, 04:07 PM   #1
JunkmanJimbo
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Default RCA led50b45rq tv backlights flash then shuts down

First of all I looked at the other posts on this model but didn't really see a solution. This is where I am so far. I have replaced the power supply and the mainboard (both used). I'm still having the same problem. The tv standby light comes on, I push the power button, the backlights flash and the tv shuts down. The tv can't be turned off unless I unplug and reconnect the power cord. I have tested the backlight strips with an LED tester and all of them are working fine. I can unplug the led connector from the power supply and the tv turns off and on like it should. Also with it unplugged, and doing the flashlight test, I can see an image in the screen. I suspect one the replacement boards is defective but I don't know which one, the power supply or the mainboard. I apologize for the long post. I look forward to any help you can offer. Thanks!
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Old 05-23-2022, 04:16 PM   #2
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Flash of backlights is a symptom of bad backlights. Your LED tester only puts out 10-20 mA and the TV can run at several hundred mA. I find it not worth it to repair RCA models since you can't find new strips for them, they have low resale value and you can't lower the backlight level in the menu (possibly in the service menu but not always). Failing LEDs may have fluctuating forward voltages (tripping the protection shutdown) and may also be slow to turn on.

Last edited by neilc6; 05-23-2022 at 04:20 PM..
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Old 05-23-2022, 04:43 PM   #3
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Thanks neilc6. I was afraid of that. So, even though the backlights work perfectly fine on high and low with a led tester they can still be bad?
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Old 05-23-2022, 04:52 PM   #4
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Default Re: RCA led50b45rq tv backlights flash then shuts down

I forgot to mention. When I first got the tv, and turned it on, it played for quite awhile until I turned it off and unplugged it. Then it started doing this crazy stuff.
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Old 05-23-2022, 05:05 PM   #5
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Default Re: RCA led50b45rq tv backlights flash then shuts down

probably backlight issue, try with tv unplugged from power, unhook cable from powerboard to mainboard, leave it unhooked, plug power cable into powerboard, plug cord into outlet, see if backlighs come on or if there's any difference, it's a simple test, may or may not work. And YES I already know it depends on if the board has pull-up resistors or not.

Last edited by nomoresonys; 05-23-2022 at 05:09 PM..
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Old 05-23-2022, 05:54 PM   #6
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Default Re: RCA led50b45rq tv backlights flash then shuts down

I've done full LED replacements on TVs with bad backlight symptoms and tested the strips afterwards and they all lit up fine. You can video the backlight flash and go frame by frame to isolate the bad LED but I suspect one or two have fluctuating voltages. I rarely do individual replacements any more since all the LEDs have wear and are likely to fail in the future. If you can get the TV to come on, you can try to lower the backlight in the service menu menu-1-1-4-7 or source-2-5-8-0.
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Old 05-23-2022, 05:54 PM   #7
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Thanks nomoresonys. I'll try that tomorrow and let you know.
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Old 05-23-2022, 05:57 PM   #8
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Quote:
Originally Posted by neilc6 View Post
I've done full LED replacements on TVs with bad backlight symptoms and tested the strips afterwards and they all lit up fine. You can video the backlight flash and go frame by frame to isolate the bad LED but I suspect one or two have fluctuating voltages. I rarely do individual replacements any more since all the LEDs have wear and are likely to fail in the future.
Thanks neilc6. Sounds like another tv going to the land field. Thanks for your help. I really appreciate it.
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Old 05-23-2022, 06:24 PM   #9
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Bigdog8882 has a youtube video on that model - https://www.youtube.com/watch?v=DtK1JhIqChw TLDW - he replaces all the backlights with another set
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Old 05-24-2022, 09:22 AM   #10
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Default Re: RCA led50b45rq tv backlights flash then shuts down

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Originally Posted by nomoresonys View Post
probably backlight issue, try with tv unplugged from power, unhook cable from powerboard to mainboard, leave it unhooked, plug power cable into powerboard, plug cord into outlet, see if backlighs come on or if there's any difference, it's a simple test, may or may not work. And YES I already know it depends on if the board has pull-up resistors or not.
nomoresonys, I tried your suggestion but nothing happened. No backlights came on.
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Old 05-24-2022, 10:46 AM   #11
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Probably time to carefully strip it down to inspect backlights. You can if you like, replace individual backlights, possibly with some from a previous salvage if they match, more are likely to fail as stated but it's a method that will only likely cost you time and not money. I would just give away or keep a tv that I repaired in this manner, because of that fact.
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Old 05-24-2022, 11:44 AM   #12
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Default Re: RCA led50b45rq tv backlights flash then shuts down

Thank you, nomoresonys, and the rest of you guys that helped me.
I did find and replaced the bad led this morning. I turned on tv and the backlights stayed on. But, unfortunately while working on the tv yesterday, I cracked the screen and didn't realize it. So, this one is going to the land field. Thanks again for all your help.
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Old 05-24-2022, 02:08 PM   #13
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Default Re: RCA led50b45rq tv backlights flash then shuts down

oh crap, hate when that happens, they are way too flimsy, seems like they could make them more durable but they probably don't want to spend a few more pennies during manufacture.
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