Just how hot can mainboard microprocessors run? - Vizio VF550M question.

[MandoZink]

Our 55" VIZIO VF550M (120Hz) quit last week. I believe I have solved how to turn it on and thus operate it, but today a somewhat hostile TV repairman told me the microprocessor was going to overheat and burn out more boards (in just 30 minutes he said) after I described what I was going to do.

I initially had no idea how to even investigate this until I watched a video on ShopJimmy.com. I am somewhat knowledgeable. I am self-taught, have repaired many devices, and have designed and built musical effects years ago. I have a decent VM with a temperature probe I had never used until today - after I talked to this unpleasant repair guy.

The TV power supply is putting out a standby 5 volt feed to the main board, but the main board won’t sending a power-on voltage to activate the power supply’s relay and kick it fully on. I jumpered the 5v standby to the correct power/on pin using a 240 ohm resistor and found the power supply turned on and worked just fine. Lo and behold, the remote and everything that worked before worked fine too, except for the On/Off button and Menu button on the side of the TV. The Input and Channel Up/Down buttons on the side do function.

My intention is to initially turn on the power supply as described with an external switch (adding an LED in series which I tested and works). Then I will turn on the TV with the remote. I intend to turn it off in the reverse order.

My question is due to the M/P heat sink temperatures I measured when I tested it and my recollections of the not-so-friendly TV tech proclamations:

This is my intended operating sequence and the temps I measured. Are these temperatures normal and/or reasonable?
All temperatures, when reached, remained stable.
22º C (72º F) - Off
31º C (88º F) - Power Supply ON
64º C (147º F) - Power Supply ON / Remote Power Button ON (took about 15 minutes to reach)
34º C (93º F) - Power Supply ON / Remote Power Back Off (took about 10 minutes to reach)
24º C (75º F) - Off

And this:
53ºC (127.4ºF) - Remote Power ONLY ON (turned off Power Supply but forgot to also turn off using remote button) Is doing this dangerous - forgetting to turn off with remote first?

ADDITIONAL INFO: My sister gave me this TV several months ago after lightning hit her outside cable line and the HDMI inputs and built-in speakers quit, which were all she ever used. I found the external audio outputs still worked and local broadcast stations came in fine. I don’t have cable, but I do stream Netflix, and the VGA input also worked. Later, after a system reset, even the HDMI inputs came back on, but the built-in TV speakers still don’t work (who cares). My sister had already replaced this TV with a 70" VIZIO by then, so I didn’t tell her about the HDMI working again.

I appreciate any observations offered on this as I am operating on a meager pension. I lack the funds for a $160+ mainboard. My big wish was that this only had leaky/bursting caps that needed replacing, but the caps looked fine.

I want to put this TV back together with some confidence before Neil deGrasse Tyson’s "Cosmos: A Space-Time Odyssey" premiers.

[tom66]

Re: Just how hot can mainboard microprocessors run? - Vizio VF550M question.

Those readings sound about right, they run the CPUs hot.
Does it have a heatsink?
I'm surprised your power-on method works - perhaps it bypasses some part of the start up process which is failing.

[MandoZink]

Re: Just how hot can mainboard microprocessors run? - Vizio VF550M question.

Thanks for the quick response. I never posted a question here before.

Yeah. It has a decent size heatsink. I took the measurements against the bottom of the heatsink. The temps I posted are actually a few degrees C below what the meter showed because my probe appears to be off calibration, reporting a bit too high.

I jumpered directly from Power Supply 5VSB pin (5volt standby) to the the Power Supply PSON pin through a 240Ω resistor and an LED, which will let me know it's on.

I am hoping my setup successfully bypassed a no-longer-functioning part of the mainboard and it will remain stable like this.

The hostile TV repair guy I talked to also kept claiming that the difference between the "hot ground" and "chassis ground" would fry the power supply. I know what the difference is and my jumper doesn't involve that. Although I did consider that he might be alluding to something I just didn't understand, I think he was just an internally conflicted and angry human being. Pretty much all of the tech friends I ever had were enthused to explain what they knew.

[tom66]

Re: Just how hot can mainboard microprocessors run? - Vizio VF550M question.

That's approximately the same experience I get when walking into a computer shop. "Where's your RAM? I need some urgently", response being "Do you want to buy some antivirus?" followed by aggressive techniques to get me to buy something I don't want leaving me more confused and upset, out of the store.

It's quite odd that your jumper works, but if it does do any damage (and I doubt it will) the worst case is the main board will stop working again. you can probably source a main board from looking through craigslist in the local areas for a smashed version of this set, for a small amount plus fuel expenses.

[Alastair E]

Re: Just how hot can mainboard microprocessors run? - Vizio VF550M question.

50-70 degrees seems to be the average for micros on mainboards Ive found...

Recently, I aquired one of those laser-guided thermometers and had a fad of checking the temperature of various make/model mainboard chips etc...

I think this is what causes the odd failure--not of the actual chip, but of that rotten lead-free solder holding it on.
They basically suffer metal-fatigue on the solder-balls and connections break between the chip and the board.
--Some makers make the situation worse--by trying to cool the chip from the other side of the board, using a dead-toad pad to the chassis.

On some sets, I have been known to add a heatsink where there was none, or increase the size of the one fitted, or even increase airflow by adding a case-fan....

[Tvbob]

Re: Just how hot can mainboard microprocessors run? - Vizio VF550M question.

Lightning hit... Be on the look out for a board you are going to need it, Good luck with the rigging.