Vizio VW42LFHDTV10...Brother Mikes TV...

[kingofcoins]

Re: Vizio VW42LFHDTV10...Final Repair De-briefing

Here's the executive summary of the problem, analysis, and successful repair of the Vizio VW42LF HDTV10:
Set had no lights, no sound, no video, doesn't respond to on/off switch, only see the amber logo and clicking heard from Power supply when plugged in.
Set has 5 boards...T-Con at top, power supply, mainboard at bottom, and an inverter board at each side...see post #1 for pics.
Repair Sequence.....
Basic problem(s), symptoms... read Post # 21
Basic set theory, Power Supply......Post # 8 & 9
Inverter Board Checking....see # 32 & 62
Re-analyses...read #64
Mainboard and final repairs...see Posts #65, 68, 70, 75-77, and 89 & 90

Service Manual location:


Thanks so Very Much To ALL who helped on this project. I will report back any further repairs if needed.
SB XLV Outcome..> Steelers 21 Packers 17

[Dgtech]

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

Nicely done!! Congrats!!

It feels good, doesn't it? You saved yourself a good bit of money and you had fun with it too, I'm sure. I'm a huge plainbill fan myself as well. Good luck on your next project.

Hey, enjoy the big game next weekend.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...>SUCCESS !!!

Hey look what I didwith YOUR help

Put in the two new LDO Voltage Regulators at U7 and U33, and 5 more 220uf caps near them on mainboard...I kept thinking it won't work, it won't work, .. and viola, it DID !

Stay tuned..> I'll get a review summary posted when time permits, pic....

[PlainBill]

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

"Upon further review", I retract my advice about replacing the caps - for now. I instead suggest they be replaced before 'buttoning up' the TV.

The output voltage of the regulators was 'unusual', and could have prevented the TV from working. The caps are very unlikely to be responsible for the unusual voltage. So replace the regulators, test the TV. If it works, go ahead and replace the caps. If it doesn't work, replace the main board.

PlainBill

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...2 more

Ok couple more things....
1). Should I be pulling and replacing these Taicon P SERIES 220UFX25v lytics, all of which I've pulled so far (8 of 9) read 0.35 ESR @ 215uf ..?

2). I did one more check on the regulators with two 95 ohm resistors in the test circuit and got 4.4V out...so it was 7.5v with no resistors, 6.5 with 480 ohms, and now this, so I've bracketed the 125 ohms they wanted but still we got nowhere close to the 2.5V spec...so is this 'purgatory' ...and lets' see what the installed parts , do or what ?

1) I would. Taicon does not have a stellar reputation. I haven't found information on their P series (possibly obsolete), but their PZ series shows an impedance of .11ohms at 100Khz. Someone else knows better than I do how that translates to ESR.
2) Might as well. I don't understand what is going on there.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...2 more

Ok couple more things....
1). Should I be pulling and replacing these Taicon P SERIES 220UFX25v lytics, all of which I've pulled so far (8 of 9) read 0.35 ESR @ 215uf ..?

2). I did one more check on the regulators with two 95 ohm resistors in the test circuit and got 4.4V out...so it was 7.5v with no resistors, 6.5 with 480 ohms, and now this, so I've bracketed the 125 ohms they wanted but still we got nowhere close to the 2.5V spec...so is this 'purgatory' ...and lets' see what the installed parts , do or what ?

[PlainBill]

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

As always Bill Thanks for the replies...
Now for the moment lets call my new parts good, what do you think the prognosis is if I install the new regulators...did we find 'anything' bad with U7 and U33 ?
What should I do next...?
I have pulled 3 more of the caps associated with the other regulators, and all 3 read 0.35 ESR for 220ufx25V, and one read only 195uf.

The voltage out of the original regulators was strange. Either they were defective, or they were limiting the output voltage because of excessive current. If you had a lab supply I would have suggested using that to provide an 'assist'. As it is, replacing the regulators is the best approach.

PlainBill

[kingofcoins]

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

As always Bill Thanks for the replies...
Now for the moment lets call my new parts good, what do you think the prognosis is if I install the new regulators...did we find 'anything' bad with U7 and U33 ?
What should I do next...?
I have pulled 3 more of the caps associated with the other regulators, and all 3 read 0.35 ESR for 220ufx25V, and one read only 195uf.

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...LDO regulator test

Bill....I'm still not clear on testing these regulators and interpreting the results. Attached my pic shows the layup I ran with 2 resistors and the battery...I tested Vout as the probes show from pin 2 to the battery ground. My battery measures 8.7V, and two identical resistors read 480 ohms each. Vout I get now is 6.5V, whereas it was reading 7.5V without the resistors.
Is this test correct ?
And if so, what do these high voltages mean ?
I got that same 7.5V on the new regulators as those I pulled.

As far as I can see, the test setup is correct. The only 'error' is for this part pin 1 is called Adj, not Gnd. The soldering looks like something I would do on a test setup.

The resistance values are higher that specified, but I'd have to review the datasheet carefully to see if that could be a problem. I wouldn't think so, it implies a great deal of current out the Adj pin.

Here are a couple of ideas to try. Try adding a 100 ohm resistor as the load. Recheck the solder joints. I can't be the only person who had what looked like a perfect joint that turned out to be open. Hook caps across the input and output. If you have them available, parallel the existing resistors with one more each - this would have the effect of dropping them down to 240 ohms.

Electronics hell has been described as when the parts test perfect, but the assembly won't work. You seem to have electronics purgatory - you can't get the parts to test perfect.

PlainBill

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...LDO regulator test

Bill....I'm still not clear on testing these regulators and interpreting the results. Attached my pic shows the layup I ran with 2 resistors and the battery...I tested Vout as the probes show from pin 2 to the battery ground. My battery measures 8.7V, and two identical resistors read 480 ohms each. Vout I get now is 6.5V, whereas it was reading 7.5V without the resistors.
Is this test correct ?
And if so, what do these high voltages mean ?
I got that same 7.5V on the new regulators as those I pulled.

[PlainBill]

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

Bill...
Should I test new regulators before I install ?
What did you think of that 7.5v out I got on the old ones ?
Any other checks tests before proceeding ?

I seldom bother testing new components. If you have a breadboard, setting up a test jig is fairly easy. You will need two resistors, ideally two resistors of 150-500 ohms and of equal value.

Note the application circuitry for the AMC1117 on page 6 of the datasheet. You can do a 'stripped down' version of that circuit. Don't bother with the caps, and substitute one of the fixed resistors for R2, the variable resistor. The other resistor is used for R1, of course. Apply 9V to the input, the output should be 2.5 volts.

PlainBill

[kingofcoins]

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

Bill...
Should I test new regulators before I install ?
What did you think of that 7.5v out I got on the old ones ?
Any other checks tests before proceeding ?

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...parts are in

Bill and others....My digi-key parts are in (under 40 hours from on line click...how do they do that for $2.12 shipping? !!)
Awaiting your further instructions on testing, checks, steps prior to installing the new 1117 regulators on the board...any ?

1. I suspect Digikey has an automated parts pulling system.

2. The US Post Office is the butt of a number of jokes by those with weak minds. The fact is they are committed to delivering First Class Mail anywhere in the country within two days. Even to an Indian tribe at the bottom of the Grand Canyon. For more routine deliveries, a highly automated sorting system helps.

PlainBill

[Dgtech]

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

I say go for it. Before power up, check all that you've touched and done. Make sure all is secure and connected. Good Luck and report back.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...parts are in

Bill and others....My digi-key parts are in (under 40 hours from on line click...how do they do that for $2.12 shipping? !!)
Awaiting your further instructions on testing, checks, steps prior to installing the new 1117 regulators on the board...any ?

[Dgtech]

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

Ok that was odd. I found a data sheet earlier that said otherwise but you are correct. I must have looked up a different version of this chip.

[kingofcoins]

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

Sorry DG my page 3 says recommended operating input is 2.7 to 12VDC:

[Dgtech]

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

Something is not right. The datasheet for this AMC1117 shows that it is - "Three-terminal adjustable or fixed 1.5V, 1.8V, 2.5V, 3.3V, 5.0V outputs".

Also, there is a chart on page 3 that shows the input voltage maximum is only 7Vdc for this chip. To do a proper test on this you may need to trim that voltage down a hair to test out the regulator - bring the 8.7VDC down to 6 - 7 Vdc .

I recently had one I wanted to test so I had one meter on the input voltage and one on the output voltage. I would then adjust the input voltage to monitor the range of the regulator and to make sure it drops out when it should.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...LDO reg's out

First time with Chip-Quik......will recommend it to all you 'heavy metal' types !

Not sure I got the right reading...here's what I did, hooked my 9v to the 1(-) and 3(+) pins, then my meter positive to the Vout pin 2, and negative to battery ground or pin 1, and read 7.5 V on both U33 and U7 chips . My battery reads 8.7V right now. Is this the right way, can't see any other way to read Vout.?

BTW, had to remove the caps C18 and C27 to do the work, and they read 0.35 ESR and 215uf (25V)...too high for me...previously they had read 0.10 and 0.07 in circuit, and appear to be a close part of the regulators loop. Guess I should take out all the caps near these voltage regulators before closing the deal.

Fixed my camera...look hand helds..>

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...take 'em out !

Hate...well yes and no...I had already consigned to the fact I didn't like the availability and price on the mainboard, and already bought the 2 inverter boards, so was getting ready for your next step in taking this one apart. In fact I found I had a pair of these type IC's . I will desolder the 2 in question and re-test, but since they are like 75 cent units, would have been putting a new ones back anyway.

While we're waiting for the 'new' test numbers, do you think these digikey voltage regulators...>http://search.digikey.com/scripts/Dk...P1117EGDICT-ND
...will work ok in place of the oem AMC1117 ?
Or would these be better required ....>?http://search.digikey.com/scripts/Dk...=497-1229-1-ND
My concern is the input voltage rating of the AP1117E I have on hand is 6.4V-18V, where as the circuit runs at 3.5-5.0 ...is this a problem ?

The parameter you are interested in is the Dropout voltage - how low the input voltage can go before the output voltage of the regulator drops. The second one has a marginally better dropout voltage AND a wider range on the input voltage.

PlainBill