Vizio M502i-B1 Power Supply Issue

[nomoresonys]

Re: Vizio M502i-B1 Power Supply Issue

Glad to hear it, damn that makes a few powerboards lately that just couldn't be solved, another eternal mystery, hate when that happens.

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Thank you budm. I wasn't sure if we were allowed to post links in the forum.

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

https://www.tvpartstoday.com/ADTVD36...tvd3613xa7.htm

Thank you budm. I wasn't sure if we were allowed to post links in the forum.

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Hey guys, it's me again. Thanks for your help on my previous questions about the power supply issues. As I stated earlier in this thread, I replaced the power supply and all seemed to be working fine until yesterday. After replacing the power supply, this TV is now doing the same exact thing it was doing before. Before replacing the power supply, I replaced the main board and the LED driver board.
Any ideas what could have caused this same issue to come back, and what could be the problem, after replacing all the boards, except the t-con board, ir sensor board and the power button board? Sorry for posting about his same TV again but I really hate to trash a perfectly good 50" TV, except for these issues, of course.

[budwich]

Re: Vizio M502i-B1 Power Supply Issue

cables / connectors? inverter board?

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Thanks budwich. Maybe I'll try to find the cable on Ebay that I've disconnecting and reconnecting. What is your opinion on that?

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

I just checked on Ebay but didn't see that particular cable. I will try looking elsewhere.
By the way, do think it's at all possible for the IR sensor board or the power button board could be causing this problem?

[budwich]

Re: Vizio M502i-B1 Power Supply Issue

those were just ideas since you appear to have changed out the two "main components" and the ultimate end result is that you are back where you started after a "degree of operation". That to me points elsewhere as the "root cause".

Not knowing much about the design but experiencing differences in the vizio versus sharp error handling and lack there of in the vizio (ie. no flash codes, just failures), I am thinking that perhaps there are some "error paths" that causes the main processor to lock down and your various powering "procedures" move around / thru these. For instance, the "force on" procedure for sharp sets is some what well known when that set type gets into certain error conditions. I am not sure that anyone is aware of anything like that for a vizio or that they have any design for such.

It would appear from your tests that the "on/off" pin shows some form of "inconsistency" when a failure happens. Have you traced that pin back to the main board to see what it touches. Not so much as a failure but to see where it goes / what processes it. Further, have you measured its resistance (to ground) with the main disconnected? The value may indicate issues with that circuit (ie. loading / open / etc).

As far as the IR board / power button board, lots of posts in and around that area for some set types that cause an issue either in terms of the 5v supply (loading) or "non-detecting" button pushes.

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

I might have failed to mention that when the issue arises, the light flashes twice and about 20 seconds later the TV will power on. Do you think those two flashes mean anything on a Vizio? Would it help if I took pictures of the back of the TV showing the boards and cables, along closeups of the main and power boards?
I have not performed the tests you mentioned but will try that to best of my ability. Thanks budwich.

[budwich]

Re: Vizio M502i-B1 Power Supply Issue

pictures are always worth a "thousand posts"... :-)

again, not knowing much but I am think that the ps-on turns on the power supply which thus powers "stuff". That "stuff" should power if it is OK... and thus the "on/off" should be sent from the inverter to the main IF the thing was successful in going through its power up ... BUT if not, then it will not be set to "on" (3.something volts). Thus, if you aren't seeing that, then its either because there is an issue with the main (which you have changed) or the inverter and subtending "circuits" there off. Of course, the main suspect would be the backlights causing issues with the inverter which ultimately cause it to not "power up" correctly. That's my "guess".... but it is just guess from very limited experience.

Some more "tests".... so you know how to get the set to some how power up correctly, right? My question to you is, if you can do this readily, unplug one of your led strings from the inverter.... try your sequence for "successful powering"... does it work or does it result in something different? Go from the result.

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Here's some pictures of the boards. I just discovered something else strange. When I drain the power holding in the power button in for about 30 seconds with the power cord disconnected, and then plug it back in, I have no power at all. I stated that earlier in this thread. But, if I quickly plug and unplug the power cord about 4 or 5 times, the standby light will come on. Then when I push power on the remote, the standby light will flash twice and then after about 20 seconds the TV will turn on. Quickly plugging and unplugging the power cord is something new that restores power. I tried different power cords and I unplugged the LED cables like you suggested but neither worked. Any ideas? None of this makes any sense whatsoever.

[nomoresonys]

Re: Vizio M502i-B1 Power Supply Issue

Looks like you changed pretty much everything but the led driver board?? some there for about 10 bucks, make sure you get a match if you get one: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Thanks nomoresonys. I have changed the LED driver board. I have changed the power supply board and the main board as well. I have taken the voltage readings. None of these symptoms make sense. Unplugging and plugging in the power cord is strange in itself to get it to power on and I just discovered that today.

[nomoresonys]

Re: Vizio M502i-B1 Power Supply Issue

Doesn't leave much but a factory reset and firmware update, unless it's a problem in the backlight circuit or one of the replacement boards was also bad??

[budwich]

Re: Vizio M502i-B1 Power Supply Issue

quote: "I tried different power cords and I unplugged the LED cables like you suggested but neither worked."

I think you need to "re try" this. Look at what I suggested... I said find a way that you can be certain to get the set to turn on / power up / run. Once you know that sequence and can be reasonably certain that it works as planned, THEN try disconnecting one of the led strings from the inverter... does the sequence still work as expected (ie. the set powers up corrrectly)? go from the results / observations (make sure you do good observations)... as sometimes things go "unsaid" and thus the forum is "blinded". ("I have changed the inverter board"... :-)... just learned ).

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

Budwich, GREAT call man. I did what you said with disconnecting the LED light strings. I disconnected one side and the TV operated normally. I plugged that one back in and disconnected the other side and then the TV started having the issues I have been describing. The standby light will blink twice and after about 15 to 20 seconds the TV will turn on. So, what do you think the issue is that's causing this? I have replaced backlight strips as well as individual backlight bulbs or beads many times in other TV's. So, do you think I have a shorted backlight strip or maybe a shorted individual light? While the TV is on, there is no indication of any backlights being burned out or any dark spots. Thank you for your help, it is very much appreciated. I look forward to your reply.

[nomoresonys]

Re: Vizio M502i-B1 Power Supply Issue

Yep, I think that's enough proof to justify investigating that side, probably just one weak led in the backlights.

[nomoresonys]

Re: Vizio M502i-B1 Power Supply Issue

And you get EXACTLY the same symptom when you have either led driver board in the set??

[budwich]

Re: Vizio M502i-B1 Power Supply Issue

probably a good question to ascertain especially since one board might have had an "operation" that rendered it "semi-functional". :-)

[JunkmanJimbo]

Re: Vizio M502i-B1 Power Supply Issue

I do have the same symptoms with either of the LED driver boards. So, you guys think I might have a weak LED backlight? And, that would cause my issues? The strange is, is that the symptoms seem to intermittent. It worked for awhile after replacing the power supply and then it suddenly starts again. If you guys feel it's likely a backlight issue, I will probably take the TV apart today.