Samsung QLED QN55Q80RAFXZA - No backlights

[Davi.p]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

why do you want to do this? Now it's important to ascertain what's wrong except power board, why don't you follow the advices? When a fuse blowns almost surely there's a short at valley so don't worry about it, leave it to background..

[nomoresonys]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

simple dim bulb tester to detect shorts and keep from blowing shit up, demonstration around 7:40: https://www.youtube.com/watch?v=wRFRwOnLsZI

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

Davi.p,

CNM801
Pin 5: VAMP = 18.1V
Pin 7: VAMP = 18.1V
Pin 11: A13V = 13.04V
Pin 13: A13V = 13.04V
Pin 13: A13V = 13.04V
Pin 17: A13V = 13.04V
Pin 16: Power On/Off = 3.3V

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

Davi.p, I don't think B13V is connected to QM884. The bottom leg is A13V but neither the top leg or middle leg is connected to B13V.

[Davi.p]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

i'm almost sure of what i wrote, and also i'm 100% sure B13v is switched somewhere from A13v and i see only QM884 can do it, so next step is yours.. c'mon..

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

Davi.p, I checked it from the top side with a digital voltmeter. All three pins were accessible. None showed connectivity to B13V

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

Davi.p,
Since I have easy access to the back side of original dead power board, I checked the trace for B13V. You are right that it goes to the center leg of QM884. I double checked again the new board that we have been debugging on the top side and it shows no connection. I don't want to peel up the glue on the bottom side sine I plan to return it as defective to hopefully get another board that works.
Will post an update after that.

[Davi.p]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

I was only suggesting you to try and make a small solder jumper on source-drain if is a mosfet or collector-emitter if a bjt, so you can right now test the entire tv.. maybe only QM884 is out of order.., i don't think somebody notice it..

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

I received a replacement power board from TVPartsToday and very pleased that the TV immediately worked. I really appreciate the insight and help on the debug of what was happening. You guys found the issue quickly which enabled me to request the replacement.

Next time I’ll start here!

[Storyteller12]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

Glad to hear you got it working. Thanks for updating everyone. Also just curious if tvpartstoday made you pay for shipping on the return or how they handled it.

There is another thread on here discussing this. So curious what your experience was

[DennisKal]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

tvpartstoday dispatched the replacement parts immediately after I submitted the form on their website. I had 5 days to determine if the replacements worked and then they would tell me the next step regarding returning the bad parts. They shipped them fast and I received them in 2 days. After I let them know it was successful they instructed me to just recycle the parts myself… no need to send them back.

On the whole, I am satisfied with my experience with them. Sure I would have liked to get working parts the first time but I recognize that we are working with parts that are not new from the factory.

[Davi.p]

Re: Samsung QLED QN55Q80RAFXZA - No backlights

The replacement boards are new only when them comes from smashed tv by the shops shipments, anyway i suggest you to test qm884 and if found to be bad replace it so you have a second working board, if qm884 marks good at diode mode of tester then something bad around the gate