Vizio VW42LFHDTV10...Brother Mikes TV...

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

OK based on your explanation then a lot of my cap readings in circuit will turn out to be marginal or high, depending on their usage, thus the need to search the cause of failure further before attacking so many caps. I'll start with the high ESR pair CE21 and CE22, as they are in the switch control circuit by the J2 connector.

My cap brands are...
On the Mainboard they are all 70 TAICON's, of several series like C0647
On the Inverters there are 4 Rubycon ZLH
On the power supply board they are mostly Nichicon (not sure series), and some Chemicon KZE's

BTW, can you provide a link for us to a table of acceptable low ESR's for caps?

You are going to have to do that yourself. Start by looking for a datasheet based on the manufacturer and series, then looking up the ESR for the capacity and voltage. Remember this is a 'better than' value. A capacitor with an ESR rating of .05 ohms might read .02.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

OK based on your explanation then a lot of my cap readings in circuit will turn out to be marginal or high, depending on their usage, thus the need to search the cause of failure further before attacking so many caps. I'll start with the high ESR pair CE21 and CE22, as they are in the switch control circuit by the J2 connector.

My cap brands are...
On the Mainboard they are all 70 TAICON's, of several series like C0647
On the Inverters there are 4 Rubycon ZLH
On the power supply board they are mostly Nichicon (not sure series), and some Chemicon KZE's

BTW, can you provide a link for us to a table of acceptable low ESR's for caps?

[PlainBill]

Re: Vizio VW42LFHDTV10...ESR the caps

Always best, yes, testing out of circuit. Good when you question 6 , 7 maybe 10 caps. But, looking at my mainboard here there are 70 caps...good chance I may hurt something,or add to the problems by undoing and re-doing that many, huh ? In such cases is there any way we can narrow our suspects down?
Now, are you saying that e.g., measuring some parallel caps in circuit will show a higher capacitance and total ESR than their individual readings when out? So if I see a cap, in parallel with say two others, and I read some multiple of its capacitance in circuit, and say the ESR read is 0.18, then its likely that none of the caps individually is over 0.18 ohms ESR, and that if they of similar make, use, and condition, the average one will be about 0.06 ohms ESR out of circuit ?
Or do I have it all backward ?

Working Update....I probed those 70 caps on my mainboard this PM and found 4 that were high in ESR, and a pair of parallel 220uf x 16V caps both reading 0.76 ESR. Would bad caps on this main/logic board be causing any of the faults.. and what would you suggest I do next...pull a leg and retest ?
...Or?

Remember the rules for parallel resistors. Two identical resistors in parallel would measure half their nominal resistance value (and have twice the power rating). Two 1K 1/2 Watt resistors in parallel would measure 500 ohms, and have a combined rating of 1 watt.

In the case of the capacitors you mentioned, a 220uF 16V cap should have an ESR below .115 ohms. Two in parallel should have an ESR below .057. (ESR is a 'better than' rating). At .76, they are more than 15 times the design specs for a low ESR cap.

As far as being responsible for the symptoms, it depends. In general terms, there are two types of power supplies; linear and switching. If these were providing filtering for a linear supply, they probably are good. If they are filtering a switching supply, they are bad. What is the brand and series of the caps?

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...ESR the caps

Always best, yes, testing out of circuit. Good when you question 6 , 7 maybe 10 caps. But, looking at my mainboard here there are 70 caps...good chance I may hurt something,or add to the problems by undoing and re-doing that many, huh ? In such cases is there any way we can narrow our suspects down?
Now, are you saying that e.g., measuring some parallel caps in circuit will show a higher capacitance and total ESR than their individual readings when out? So if I see a cap, in parallel with say two others, and I read some multiple of its capacitance in circuit, and say the ESR read is 0.18, then its likely that none of the caps individually is over 0.18 ohms ESR, and that if they of similar make, use, and condition, the average one will be about 0.06 ohms ESR out of circuit ?
Or do I have it all backward ?

Working Update....I probed those 70 caps on my mainboard this PM and found 4 that were high in ESR, and a pair of parallel 220uf x 16V caps both reading 0.76 ESR. Would bad caps on this main/logic board be causing any of the faults.. and what would you suggest I do next...pull a leg and retest ?
...Or?

[retiredcaps]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Many power supply designs have a number of caps in parallel. Measuring the ESR is tricky. My best suggestion when measured capacitance is a multiple of a single capacitor is to test the ESR of each out of circuit.

A video explanation of this is at

http://www.youtube.com/watch?v=4iTR-iCn0hY

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Bill... Thanks for coming in and you have a GREAT New Year !!

Some of the confusing symptoms and readings are no doubt from bringing the caps out of 9 months idle storage and 'warming' it up. When I first tried set plugging in and out, the switch had no affect, and the clicking pattern was different. Now that its 'awake', the switch seems to jump up the main supply, but only after a few seconds delay, which then reads 400VDC btw, the logo goes white, and it's only then that I read the 24v and 1.8v at the inverters, and 12v, 5v and 3.3v to the main board. Otherwise its only 5VDC output to mainboard during standby. And switch fails to turn set off.

Now the cold boot test ..set off about 45 mins, meter on pin 14 of J7, plug in, the logo stays amber even though the double click is heard. plugging and unplugging deflects meter slightly but does not get white logo until switch is pressed even then only after a few seconds delay. When logo white, meter shows slight drop in signal ohms. Pull plug and reinserting on several attempts failed to get the white logo back...only way is pressing switch and waiting.

All the lytics on the power and inverter boards where checked in circuit with 'Russian Mikes' ESR meter, each would read like 0.02 or so but the capacitance would show as some multiple. Advise if we need also a volt or ohm check on them. The hair dryer on the main board caps didn't produce a thermal response. And I did not ESR check any on the main/logic board, yet...there are about 70 of them ...advise.

Other notes:
I read there is supposed to be a blue led on inverter boards when lamps light up. I of course see none.
I've read Vizio says inverter boards are integral part of display, and not repairable....this is not true as there are two separate removable boards.
Do I need to plug in the TV cable during any tests...LMK.
I haven't seen any back lights or image either way so far.
There is 6. VDC at the speaker wires from mainboard.

I'm going to be shutting down for an afternoon of watching football (the type played with an oblate spheroid), so this will be brief. Here's a little information on the typical start up sequence.

Initially the power cord is plugged in, and the standby supply is providing 5Vdc. The power button is pressed, and the standby processor carries out a series of health checks, then turns on the the main supply. The PFC boosts the rectified line voltage to 400 VDC, and the main SMPS comes up. Once these voltages are stable the main processor is started, and begins it's own self tests.

Many power supply designs have a number of caps in parallel. Measuring the ESR is tricky. My best suggestion when measured capacitance is a multiple of a single capacitor is to test the ESR of each out of circuit. As a quick alternative, multiply the measured ESR by the number of caps in parallel. As an example, 1000uF 16V FM series has an ESR of .02, three in parallel should read .007.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Bill... Thanks for coming in and you have a GREAT New Year !!

Some of the confusing symptoms and readings are no doubt from bringing the caps out of 9 months idle storage and 'warming' it up. When I first tried set plugging in and out, the switch had no affect, and the clicking pattern was different. Now that its 'awake', the switch seems to jump up the main supply, but only after a few seconds delay, which then reads 400VDC btw, the logo goes white, and it's only then that I read the 24v and 1.8v at the inverters, and 12v, 5v and 3.3v to the main board. Otherwise its only 5VDC output to mainboard during standby. And switch fails to turn set off.

Now the cold boot test ..set off about 45 mins, meter on pin 14 of J7, plug in, the logo stays amber even though the double click is heard. plugging and unplugging deflects meter slightly but does not get white logo until switch is pressed even then only after a few seconds delay. When logo white, meter shows slight drop in signal ohms. Pull plug and reinserting on several attempts failed to get the white logo back...only way is pressing switch and waiting.

All the lytics on the power and inverter boards where checked in circuit with 'Russian Mikes' ESR meter, each would read like 0.02 or so but the capacitance would show as some multiple. Advise if we need also a volt or ohm check on them. The hair dryer on the main board caps didn't produce a thermal response. And I did not ESR check any on the main/logic board, yet...there are about 70 of them ...advise.


Other notes:
I read there is supposed to be a blue led on inverter boards when lamps light up. I of course see none.
I've read Vizio says inverter boards are integral part of display, and not repairable....this is not true as there are two separate removable boards.
Do I need to plug in the TV cable during any tests...LMK.
I haven't seen any back lights or image either way so far.
There is 6. VDC at the speaker wires from mainboard.

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...repair manual

PlainBill and ALL you VERY helpful folks....
> HAVE A SUCESSFUL AND VERY RE-PAIRABLE HAPPY NEW YEAR !!

BILL..> I did find a service manual at Elektro Tanya here :



Would you help me on this diagonsis and repair please ?

Well, I can explain some of the readings you describe. 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

Now, I'm having problems explaining the symptoms you are seeing. Usually when the standby processor turns on the main supply it verifies the voltages are correct, then initializes the main processor(s). If an error is found it will shut down the main supply and possibly flash an error LED.

The fact that the main supply will sometimes shut down again and other times will stay up is characteristic of bad caps, especially if after several repeated attempts it will stay up. Theorizing that the DC out of the power supply is noisy, thus causing stability problems for the main board would seem logical. The fact that you checked the ESR of all caps and found them good shoots a rather large hole in that theory.

I have two tests to propose. First, start with a 'cold' set - one that has been unplugged for at least half an hour. Monitor the 'Power On' signal at the connector from the main board. Plug in the TV and see if the signal behaves consistently through several attempts to power up, until it does go into the white Vizio logo. Unplug the set and try again. Does it go to the white logo on the first attempt? If so, that would imply that something is warming up and working when it is warm. Again, this is characteristic of a marginal cap. If on the other hand, it seems to be more random (it would go to the white logo about 20% of the time), it would suggest something else is the problem.

If it DOES appear to be a thermal problem, the second test would be to use a hair dryer to warm various points - the caps in the power supply, various parts of the main board, etc, and see if there is a particular area that appear to be thermally sensitive.

If it doesn't appear to be thermal, try flexing various parts of the main board slightly to see if that has any effect.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...update

Update on my progress...I found after several plug in trials that the unit does regularly produce the 5VSB supply to the logic board, and the double click I hear is apparently the power supply failing to make or maintain the 12v and 24v connection. After several more tries it happens that instead of kicking right out it will hold then a few seconds later a second click will result in the logo going to white and then I read the 12v and 24 volt out of the p/s board. This however is as far it goes, no lights, and unit will not turn off.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...repair manual

PlainBill and ALL you VERY helpful folks....
> HAVE A SUCESSFUL AND VERY RE-PAIRABLE HAPPY NEW YEAR !!

BILL..> I did find a service manual at Elektro Tanya here :



Would you help me on this diagonsis and repair please ?

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Anybody have a link to schematics or repair manual for this Vizio?

Nothing from my usual free sources. You could try some of the paid sites.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Anybody have a link to schematics or repair manual for this Vizio?

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV needs help

Being new inside a TV I realize they would have more circuitry features than an LCD monitor, but am at a loss about multiple power sources. Do you mean my finding a variable voltage output at the main cap could be part of the scheme and not a failure ?

[retiredcaps]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

All the bridge rectifier leg pairs read 16 to 19 ohms in circuit except the A/C pair is infinity.

In theory, I understand what a bridge rectifier does and I have certainly helped others here identify bad ones (in fact, just one today) with successful repairs as a result.

So if you measured (with power off and tv unplugged) pins 1-2, 1-3, 1-4, 2-3, 2-4, and 3-4 and found 16 ohms on even one pair, I would say this bridge rectifier is shorted.

However, I'm not so sure about it being shorted with your findings of 161V DC and a fuse that measures 0 ohms.

On TVs, I know there are multiple power sources. A standby 5V, the main power, and a potential PFC (which I'm still learing about).

[kingofcoins]

Volunteering with this as my first TV project, but I believe it is repairable...and it would appear PlainBill also likes these challenges too:
Brother Mike reports some squiggly lines , then it gave a whine, and went black. Now as cord is plugged in the amber light comes on, and after 5-10 seconds there is a double click, which sounds like first the main filter cap, then the bridge rectifier clicks. Unit does not respond to shut off switch, pulling plug and reinserting repeats symptoms. The cap has 161VDC, but when the click occurs it goes to 300+ VDC. Output to Inverter boards is zero until the double click occurs, then it swings to about 12VDC and falls away to 2-3 v, same thing occurs with logic feed.
Main fuse 0+/-; all caps on p/s board , and the pair on each inverter board , all read low ESR's in circuit. All the bridge rectifier leg pairs read 16 to 19 ohms in circuit except the A/C pair is infinity.
Pics show the p/s board has a lot of soldered in heat sinks; the bottom view is of the p/s.
PS...I have an ESR meter, but only a analog VOM right now....THANKS for your help !