Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

[imamachine]

I am attempting to assist a friend with her TV repair. The screen went blank and will not come back on. She pulled the power supply out and I took a look at it. The first components down stream of the power cord (besides a fuse which tested good) are a Metal Oxide Varistor and a Thermistor. The MOV has a scorch mark on the side which you can just see in the photo.

I am by no means a tech guy...everything else on the board (and the inverter board, including the fuses on it) looks fine so my solution is to simply replace these two items and see what happens.

I cannot find these exact components. I have spent hours trying to find replacements for these and, well, I don't really know how to compare them, there are so many parameters and I can't find anything that matches exactly. So my questions are, 1. What parameters do I really need to focus on, and 2. How close does the replacement part have to be?

The MOV is marked, TVR 14561 and the Thermistor is marked, SKC 2R56. Here are some links that describe these components:
http://www.alibaba.com/product-gs/36..._TVR14561.html



I am considering replacing these components with these I found at DigiKey:
http://search.digikey.com/scripts/Dk...50tse&x=8&y=15
http://search.digikey.com/scripts/Dk...2-nd&x=13&y=14

Are these good enough? Any suggestions?
Thanks in advance!!

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

The screen went blank and will not come back on.

Some simple questions first to help determine where the problem is.

1) Did the power LED come or stay on when the screen went black?

2) What does the power LED do NOW when you plug in the TV?

3) Do you have a multimeter and some experience in using it?

4) Please post pictures of all your boards so we can see each board individually and an overall shot so we can see the relationship between boards.

[Pyr0Beast]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Well. If MOV is of wrong value it will either not protect the device or burn itself off. No problem there.

[Toasty]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Choices look fine going by the datasheets for the originals.

Was the TV subjected to a power surge or lightning strike in the area when it failed?
Usually the only way a MOV ends up scorched...

If the thermistor looks good (not cracked) and shows continuity, it's not bad.

With the fuse still good, I doubt the MOV is bad and the scorching/discoloration is probably a result of being in close proximity to the thermistor, which can run warm-hot.

I would be checking for LED flash codes, as retiredcaps suggested, to indicate the failure board.

I can't locate a Service Manual for this. How old is the set?

Toast

EDIT: Walmart still shows this available for $259. Warranty?

[imamachine]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Some simple questions first to help determine where the problem is.

1) Did the power LED come or stay on when the screen went black?

2) What does the power LED do NOW when you plug in the TV?

3) Do you have a multimeter and some experience in using it?

4) Please post pictures of all your boards so we can see each board individually and an overall shot so we can see the relationship between boards.

1. Not sure, she doesn't remember
2. Nothing, the LED doesn't come on at all
3. I have a smaller one and I'm okay with it. I also have a couple of different Fluke meters at work

I'm not sure on the set's age, but it is out of warranty.
I found a replacement power supply board online for $48. If I can narrow the problem down to that I'm okay with just buying a new board...but it would be interesting to also find out what exactly what went bad.

Here are some additional pics of the boards, thanks for the help!!

[Toasty]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Check voltage across large cap. Meter in 500v or better scale.

Check if any voltages are there on right side (of the black line) of board in the 3rd pic. I see marked voltages on at least the upper right connector.

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

I found a replacement power supply board online for $48.

Most of us here tend to try to repair rather than replace. If we can replace for 48 cents, we get a sense of pride versus spending $48. No guarantees though.

Here are some additional pics of the boards, thanks for the help!!

Great pics. I can even see the pet hair on the carpet!

On CN902, it looks like pin 10 is STB (standby). This should be 5V DC. Without this voltage, nothing will work.

As for the age of the set, there are date codes on the caps. It might listed on the sleeve as 0832 which would indicate 2008, week 32. I can't tell from the angle of the pics, but that will give you an idea of how old the set it.

[Pyr0Beast]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Can you just check if there are any voltages present on the output of the power supply ?

If not. Check primary - Diode bridge - There should be about 300V on the main capacitor. Probably main switching chip+mos went into digital heaven.

[severach]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

The inverter and power board have date codes in large print.

[imamachine]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Thanks for all the replies!

I get 167v across the big cap (less than the 300v quoted from PyroBeast)
I get nothing on the right side of the power board except for C902 and IC903.
Thus, I also do not get 5v on the standby pin at CN902.

Hmmm (scratch head)...now what?

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

1) Getting 167V DC implies that everything from the AC plug to C907 is working fine. 120V AC mains x 1.4141 = 169V DC. So your reading is close enough.

2) The absense of secondary voltages on the connectors implies that something inbetween C907 and connectors is failing. It could be a number of things. Below is a starting point.

3) Due to the angle of the caps in the picture, I can't tell the PCB designations so I marked up 4 capacitors in different colors.

Measure the DC voltage across each capacitor. Put your black probe on the negative side of the cap and your red probe on the positive side of the cap.

List their color, voltage, and PCB designation for all caps.

For example,

Blue = C915 = 10V DC steady

4) We will also need a clear focused picture of the backside of the power board.

5) Also list the

a) brand
b) series
c) uF
d) voltage

for each of the color circled caps. For example, blue might be Samxon GT 47uF 25V.

6) When you are measuring for voltage on the connectors, where are you placing the black probe? In other words, what did you use as ground?

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

7) In the upper left hand corner of the power board picture, there is a IC sitting on the heatsink (next to the red square cap).

a) Can we get a photo of that?
b) What is the part number?

[Pyr0Beast]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

>1) Getting 167V DC implies that everything from the AC plug to C907 is working fine. 120V AC mains x 1.4141 = 169V DC. So your reading is close enough.

I think this unit has PFC so it should be around 300V anyway.

Can you 'load' it with, let's say ... 50W lightbulb and see if voltage collapses ?

Might be a faulty diode.

[Pyr0Beast]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

> 7) In the upper left hand corner of the power board picture, there is a IC sitting on the heatsink (next to the red square cap).

Should be a diode bridge

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

I think this unit has PFC so it should be around 300V anyway.

Yes, I agree that this likely has a PFC and that voltage should be around 300V DC after the set has turned on.

PlainBill does an excellent job of describing how most LCD TVs power supplies work at

https://www.badcaps.net/forum/showpo...90&postcount=8

The basic design of this power supply is pretty standard for TVs of this size. AC in goes through an input noise filter and surge protection, then into a bridge rectifier and produces about 165VDC across the main filter cap. This is used to power a standby power supply, which is always on when the TV is plugged in. The output of the standby supply goes to the main board, and provides power for the standby processor and associated components, mainly the IR receiver, and keypad.

When the TV is turned on via either the remote or the keypad a signal is sent back to the power supply which turns of the PFC (power factor correction) front end and the main supply. The PFC 'chops' the rectified AC and boosts it to about 300-350 VDC. The main supply produces the 5V and 12V supplies for the main board and the inverter. Either 5V or 12V is used to provide other voltages (3.3V, 2.5V, 1.8V) used on the main board

[imamachine]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

1) Getting 167V DC implies that everything from the AC plug to C907 is working fine. 120V AC mains x 1.4141 = 169V DC. So your reading is close enough.

2) The absense of secondary voltages on the connectors implies that something inbetween C907 and connectors is failing. It could be a number of things. Below is a starting point.

3) Due to the angle of the caps in the picture, I can't tell the PCB designations so I marked up 4 capacitors in different colors.

Measure the DC voltage across each capacitor. Put your black probe on the negative side of the cap and your red probe on the positive side of the cap.

List their color, voltage, and PCB designation for all caps.

For example,

Blue = C915 = 10V DC steady

4) We will also need a clear focused picture of the backside of the power board.

5) Also list the

a) brand
b) series
c) uF
d) voltage

for each of the color circled caps. For example, blue might be Samxon GT 47uF 25V.

6) When you are measuring for voltage on the connectors, where are you placing the black probe? In other words, what did you use as ground?

1. What is the significance of 1.4141?
3. Yellow, CapXon, P904, 1uF 450v, C961, 166.5v steady
Green, Only brand marking is JH inside an oval, CD263 100uF 25v, C916,
37.6v steady
Red, CapXon, P908, 33uF 50v, C920, 10.7v steady
Blue, CapXon, P908, 33uf 50v, C915, 6-9.5v varying
4. Attached, hopefully with less dog fur!
6. I put the black lead on each of the pins marked ground. I also installed the board back intothe TV and touched several places on the chasis.
7. The part number on that is GBU606

Regarding the suggestion to attach a load, where should I do this?

I will be out all next week but I look forward to hearing anything further, thanks!

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

1. What is the significance of 1.4141?

Never took any EE course so I don't know the exact explanation. I just know how to apply it.

Red, CapXon, P908, 33uF 50v, C920, 10.7v steady
Blue, CapXon, P908, 33uf 50v, C915, 6-9.5v varying

Capxon doesn't have a very good reputation here. The fluctuating C915 voltage may be the reason why the SMPS isn't starting. The voltage should be a solid value. So replace C915 and C920 (because it is Capxon).

I recommend Panasonic FC, digikey part number P10320-ND

http://search.digikey.com/scripts/Dk...name=P10320-ND

If replacing these caps doesn't work, it could be the SMPS chip itself, but try the caps first.

Also, if the caps work fix the problem, most here will recommend that you replace ALL the Capxon electrolytic caps with Panasonic FR/FM or FC. If you are in the USA, shipping from digikey.com is only about $2.75 and you get the parts in about 48 hours via USPS first class mail.

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

Green, Only brand marking is JH inside an oval, CD263 100uF 25v, C916,
37.6v steady

Hmm, I just noticed the readings on this cap. This cap could be a problem too. The cap is rated for 25V and the voltage is 37.6V DC. Assuming you made no typos or errors, this cap should have exploded.

Let's also change this cap to a 100uF 50V just in case.

I recommend the Panasonic FM cap

http://search.digikey.com/scripts/Dk...name=P12392-ND

So at minimum, you should order 3 caps.

[retiredcaps]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

In post #18, I say order 3 caps. I mean

qty = 2 = Panasonic FC 33uF 50V
qty = 1 = Panasonic FM 100uF 50V

in case you thought I meant three 100uF 50V.

BTW, PlainBill has lots of expertise in this area, but may not have seen this thread at all because it is not in the "Troubleshooting TVs and Video Sources" section.

Also, I would be remiss if I didn't mention that PCBONEZ talks about how to choose caps at

https://www.badcaps.net/forum/showpo...30&postcount=7

[Pyr0Beast]

Re: Sourcing Replacment MOV and Thermistor for Vizio VA26LHDTV10T Television

This is PFC suppy for sure now.

PFC part does not start - check mosfet, check diode, check power supply of the ic.