Vizio 42" Plasma 5+ Min. Warm Up

[nickelflippr]

I'm having a crack at fixing a Vizio (P42HDTV10A) 42" Plasma tv, which in turn uses an LG PDP42X32000 screen and associated driver boards. Found a couple of power supply caps that had slight bulges (Nichicon 330uf 450V) and replaced those. Also found a Taicon 1000uf 16V that was definitely bad on the tuner board, and replaced that.

With this model you can short a couple pins on the AUTO GEN plug to display an internal pattern, and I did so. Patterns were fuzzy/snowy for several minutes and slowly got better and better till a decent picture/pattern arrived. Pulled the test and hooked up a Direct tv box, and have the same thing, slow startup till decent picture. On occasion a loud burst of static over the speakers happens.

Took power board readings and all the 5, 9, 12, 24V rails look good. The Vsc, Vy, Va, and Vs look good too. In taking the Xsus voltages, my probe slipped and took out the 5V 10A smd fuse on the Ysus board. Fixed that, hope I didn't take anything else out?

So any thoughts on what direction to take this? Don't have a scope handy to test ripple or waveforms. Here's a pic of the startup condition.

 

[Pommie]

Only thing I can suggest is a freezer spray to try to recreate the "cold" picture.

Mike.

 

[tunedwolf]

I would suggest regulation on the signal board looks poor for some reason, however I got caught out with one last year that looked similar, turned out to be the T-Con board.

 

[nickelflippr]

Thanks for your replys. Could the conditions suggest more bad caps someplace? Do people take a shotgun approach by doing wholesale recapping of boards?

@Pommie
Good idea on the freezer spray, hadn't thought of that. If I shut off the set after it has warmed up then there are flashing pixels in the white areas. So do you apply spray while the set is powered?, and where?, the ipm module heat sinks, Y driver fets, whole boards ....?

@tunedwolf
So the signal board meaning the control board? The control board is underneath the tray holding the tuner (small board) and main board (large board) in the bottom center of the pic, kind of hard to diagnose as cables have to come off to get to it.

Even after the tv warms, up there seems to be some subtle horizontal defects. So if the freezer spray doesn't isolate the Ysus and Ydriver boards, then the control board makes sense.

 

[tunedwolf]

Yup, the T-Con is usually buried under all the metalwork and bolted right to the back of the screen
I would only consider "shotgunning" caps in a power supply, only because it's likely to be beneficial in the absence of an ESR meter.
The lasting picture defects could be a Sus board adjustment out of wack, or one of the IPM modules faulty or back to the control board again. The only real way to tell if it's an adjustment would be to hook up a scope and make sure all trimmers are correctly set, or by substitution. What I sometimes do to save time, and money if I'm not on the problem within 40mins, is just buy in a service kit. It comes as both Sus boards and a control board. I will then sell on the old working boards on the 'bay.

 

[nickelflippr]

Tried the freezer spray today on the power supply board caps, ipms, Ysus fets, mainboard ic, and control board ic the best I could. Was not able to find anything. Thought I would try a hairdryer in the next day or two, to see if the opposite approach helps out over the 5+ minute startup problem.

May try to check the control board voltage regulators when I get it flat on its back again, and recheck the Ysus fets again too.

Not having the necessary tools handy is a pain, so board replacement approach may be the way things have to go. Will update as things move along.

P.S. The Vs (supply) is 187.6V against a 186V sticker value, surely that can't make a huge difference?

 

[Nigel Goodwin]

Tried the freezer spray today on the power supply board caps, ipms, Ysus fets, mainboard ic, and control board ic the best I could. Was not able to find anything. Thought I would try a hairdryer in the next day or two, to see if the opposite approach helps out over the 5+ minute startup problem.

May try to check the control board voltage regulators when I get it flat on its back again, and recheck the Ysus fets again too.

Not having the necessary tools handy is a pain, so board replacement approach may be the way things have to go. Will update as things move along.

P.S. The Vs (supply) is 187.6V against a 186V sticker value, surely that can't make a huge difference?

Adjust it to be correct and see if it makes any difference.

 

[sparkman001]

Replace ALL the electrolytics on the secondary side of the psu, that should sort out the slow start-up. Hope this helps

 

[nickelflippr]

Replace ALL the electrolytics on the secondary side of the psu, that should sort out the slow start-up. Hope this helps

So replace the 20+ caps on the main PSU board, and the 8 caps on auxilliary PSU board? You have noted this condition before, or an educated guess?

I did end up replacing the TAICON 1000uf 16V on the single switching supply for the main board, but still no change in the picture.

Thanks everybody for the suggestions, keep them coming.

 

[sparkman001]

Thats exactly what I'm saying, you need to replace them all. Use only high quality low ESR branded devices, not some cheap Chinese rubbish. I only use 105deg caps as they are far more reliable. You need to ensure that you have no ripple on the supply lines as this plays havoc with the digital devices on the signal processing boards. If you can 'scope the voltage supply rails to make sure. Always get the psu sorted first.

 

[nickelflippr]

@sparkman001
Yes, I understand about the high quality caps. I was using the Panasonic FR series, like the EEU-FR1E102 to replace the 1000uf 16V Taicon's.

I'll have to write up a BOM for the caps. This is a friends tv, so need to run the costs by him first, before proceeding.

 

[Nigel Goodwin]

So replace the 20+ caps on the main PSU board, and the 8 caps on auxilliary PSU board? You have noted this condition before, or an educated guess?

I did end up replacing the TAICON 1000uf 16V on the single switching supply for the main board, but still no change in the picture.

Thanks everybody for the suggestions, keep them coming.

If you haven't got an ESR meter, then blanket change them - it's the MOST common fault these days, cheap capacitors going high ESR.

As sparkman001 says, replace them with high quality, high temperature. low-ESR ones - Panasonic or Rubicon are good choices.

I've kept nothing but 105 degree caps at work for years now.

 

[nickelflippr]

@Nigel Goodwin
Well blanket changing caps could be a good down payment on an ESR meter? Any suggestions for an economical to moderate priced model? Is the ESR readings normally taken in circuit?

 

[Nigel Goodwin]

@Nigel Goodwin
Well blanket changing caps could be a good down payment on an ESR meter? Any suggestions for an economical to moderate priced model? Is the ESR readings normally taken in circuit?

Yes, you can mostly check them in-circuit.

This is the one I use at work:

https://www.peakelec.co.uk/acatalog/jz_esr60.html

 

[sparkman001]

I've had a couple of pm's about what I've said. In reply, Id like to say if you rely totally on an ESR meter, no matter how good, you will not sort psu s on some of the modern lcd/plasma tvs. A decent one will cost about £200/$300 and you will change an awful lot of caps for that price and still won't be absolutely sure that you have reliability and no returns. If its not your tv, someone else is paying so its not your problem! If it is your tv the caps are cheap and your labour is cheaper still! My logic I suppose but it works for me.

 

[nickelflippr]

@Nigel Goodwin
Thanks for the recommendation on the ESR meter, I will keep that for future reference. If I happen to do more than a couple of these, then that will be on my buy list.

@sparkman001
I understand the logic, and not being in this as a business, I want to watch the costs.

 

[Nigel Goodwin]

I've had a couple of pm's about what I've said. In reply, Id like to say if you rely totally on an ESR meter, no matter how good, you will not sort psu s on some of the modern lcd/plasma tvs. A decent one will cost about £200/$300

The one I posted the link to is absolutely excellent, and only a fraction of those prices - comes from been PIC based

and you will change an awful lot of caps for that price and still won't be absolutely sure that you have reliability and no returns. If its not your tv, someone else is paying so its not your problem! If it is your tv the caps are cheap and your labour is cheaper still! My logic I suppose but it works for me.

A professional attitude is to change ALL the caps, to give a lasting repair! - if you only change the ones that were faulty that day, you'll be doing it again in afew weeks!.

 

[electronicsfreak]

If you have access to a Scope/Function Generator you may be able to check for Capacitors yielding that unwanted ESR.
Here's a short Demo of what I'm talking about:https://www.youtube.com/watch?v=-CTXZ5lsnjA&list=UUU6e-GTO7O74gIG6cWiHYZA&index=2&feature=plcp (Note to anyone viewing this: I am currently an engineering student. If you see any information I had presented incorrectly in this video, please give me flak for it, and I'll fix it)

 

[nickelflippr]

Thus far have changed the auxilliary PSU board caps, which in turn supplies a 12 or 13 volt rail, plus a 5V rail to the main board. When I fired up the set, several snapping sounds were made, and shut off immediately, uh, oh. Pulled board, rechecked all cap polarities, fuse, bridges, burning and found nothing. Is that normal? May have been too liberal with the RTV around the caps, so cleaned that up. Refired it up and back to the same problem as stated in post #1. Need to consider recapping the large PSU board now.

One thing I noticed over time, is when the short static bursts from the speakers happen is when the background is largely a bright white. So power draw sounds like at least one of the problems, with the audio circuit, or control, starving out on the main board.

@electronicsfreak
Thanks for the tip, but no scope as mentioned previously in this post.

 

[nickelflippr]

Replaced all electrolytics on the main power board, still no change, so on to board changing.