Onn 100021261 65" TV turns on, shows logo and gets stuck in boot loop

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Hisense Television

Repair documentation and service information for Hisense televisions.

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Dobbyisfree @dobbyisfree

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Posted: Aug 17, 2025

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Onn 100021261 65" TV turns on, shows logo and gets stuck in boot loop

I have this Onn 65" Roku TV that seems to be stuck in a boot loop.

Here's what I noticed so far. If I turn off the TV for a couple of hours and then turn it back ON, it stays ON for 2-3 minutes, then turns OFF. When I turn it back ON, it shows the "ONN Roku TV" logo, turns OF, the red light on the power button blinks twice, turns back ON automatically, and repeats in a loop.

Please note: I'm posting this question under Hisense TVs because the internal power board is manufactured by Hisense Electric.

I have opened the back cover and checked for any bad capacitors, but couldn't find any.

Here are some pictures. There's no issue with backlights or the screen. There are no devices connected to the TV.

Could someone please help me troubleshoot the issue? Feel free to let me know if you need more information.

Update (08/18/2025):

Added legend for the power board

Update (08/19/2025):

Measured voltages on the Pins

Update (09/13/2025):

Disassembled the TV completely to check the LED backlights. Turns out one of the LEDs was burnt.

Replaced that LED strip, and it fixed the issue.

Answered! View the answer I have this problem too

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@dobbyisfree let's see the legend for your main board connector. That is printed on your power board to the left of the connector.

Onn is a bit off-brand so schematics are really not available. It is possible that this is a firmware issue or a power board issue. Not even sure where you would get ONN firmware but lets see if we can find it :-)

Aug 17, 2025 by oldturkey03

@oldturkey03

I do not see any other legend apart from the one shown in my first photo. I added a new photo with a clear legend. Please let me know if this is what you are looking for.

Also, Onn TV uses Hisense power board. So I'm assuming it should follow Hisense schematics if they are available.

And I think this is where we can find the firmware for Onn https://tvupdate.roku.com/

Aug 18, 2025 by Dobbyisfree

@oldturkey03 Yes, I've already added this legend in photos. See my last closeup photo. Modified the description to show under "update"

Aug 18, 2025 by Dobbyisfree

@dobbyisfree sorry, I guess I must have missed that. Now use your multimeter and measure the voltages on the contacts that show 12V as well as ANA, VAMP and SW. Those should all be positive voltages. Place one probe on ground and the positive probe from your meter on the contact. sometimes you can do that by inserting the probe with the cable (if your probe is small enough). Other times you have to loosen the board and measure the voltages from underneath the board. A bit cumbersome and be careful not to get zapped. The power supply packs a punch by the capacitors.

Aug 18, 2025 by oldturkey03

@oldturkey03 No problem at all.

Thanks, I will measure the voltages tomorrow after work and share here.

Aug 18, 2025 by Dobbyisfree

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Dobbyisfree @dobbyisfree

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Posted: Sep 13, 2025

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Disassembled the TV completely to check the LED backlights. Turns out one of the LEDs was burnt.

Replaced that LED strip, and it fixed the issue.

Update:

Somehow, the outer frame of the TV is not fixed properly over the LCD screen. I see a bulge on the left side of the TV. It's not evident from the front, but when the TV is ON, I see the light as shown below.

There was some kind of glue holding the frame in place. Now, even though I press the frame, it doesn't want to stay.

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@oldturkey03 Do you know if there is a way to fix it?

Oct 18, 2025 by Dobbyisfree

@dobbyisfree is there a possibilities that something got pinched or that one of the plastic "lips" is deformed? Is it possible tha tthe cover itself is slightly deformed? If there is nothing that prevents it from closing, I would use some dabs of adhesive (other than "super glue") and press it closed, using some strong adhesive tape to keep it in place until the adhesive is cured. Of course, you will need to remember to use some het to soften the glue if you ever have to open the TV again.

Oct 19, 2025 by oldturkey03

@oldturkey03 there's nothing preventing it from closing. If I push the frame it closes, but it doesn't stay closed. The frame is not deformed. I'm thinking I might have pushed on the corner. What adhesive do you recommend for this?

Oct 19, 2025 by Dobbyisfree

@dobbyisfree I'd use something like B7000

Oct 19, 2025 by oldturkey03

@oldturkey03 Thanks, I had never heard of this before, will give it a try!

Oct 19, 2025 by Dobbyisfree

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@dobbyisfree let's see the legend for your main board connector. That is printed on your power board to the left of the connector.

Onn is a bit off-brand so schematics are really not available. It is possible that this is a firmware issue or a power board issue. Not even sure where you would get ONN firmware but lets see if we can find it :-) — oldturkey03
@oldturkey03

I do not see any other legend apart from the one shown in my first photo. I added a new photo with a clear legend. Please let me know if this is what you are looking for.

Also, Onn TV uses Hisense power board. So I'm assuming it should follow Hisense schematics if they are available.

And I think this is where we can find the firmware for Onn https://tvupdate.roku.com/ — Dobbyisfree
@oldturkey03 Yes, I've already added this legend in photos. See my last closeup photo. Modified the description to show under "update" — Dobbyisfree
@dobbyisfree sorry, I guess I must have missed that. Now use your multimeter and measure the voltages on the contacts that show 12V as well as ANA, VAMP and SW. Those should all be positive voltages. Place one probe on ground and the positive probe from your meter on the contact. sometimes you can do that by inserting the probe with the cable (if your probe is small enough). Other times you have to loosen the board and measure the voltages from underneath the board. A bit cumbersome and be careful not to get zapped. The power supply packs a punch by the capacitors. — oldturkey03
@oldturkey03 No problem at all.

Thanks, I will measure the voltages tomorrow after work and share here. — Dobbyisfree
@dobbyisfree is there a possibilities that something got pinched or that one of the plastic "lips" is deformed? Is it possible tha tthe cover itself is slightly deformed? If there is nothing that prevents it from closing, I would use some dabs of adhesive (other than "super glue") and press it closed, using some strong adhesive tape to keep it in place until the adhesive is cured. Of course, you will need to remember to use some het to soften the glue if you ever have to open the TV again. — oldturkey03
@oldturkey03 there's nothing preventing it from closing. If I push the frame it closes, but it doesn't stay closed. The frame is not deformed. I'm thinking I might have pushed on the corner. What adhesive do you recommend for this? — Dobbyisfree
@oldturkey03 Thanks, I had never heard of this before, will give it a try! — Dobbyisfree