p42hdtv10a - No Picture, No Sound

[Xwell]

Hello All,

Long time lurker, first time poster.

Thanks for a great resource for people like me who don't think a marketplace built around "disposable" goods is such a good thing. Then again, I suspect most hoarders believe the same thing. Boy, don't let my wife know of my realization....



I've had this set back-benched for a while now, and I've made a promise to myself that I'd concentrate on getting it working (or proving that its beyond repair). I've followed a few of the posts on this forum and think I have narrowed it down to the Y-sus board. After reading through a few posts (on this and other forums) I found this post:

https://www.badcaps.net/forum/showth...ght=p42hdtv10a

I've worked my way through most of PlainBill's suggestions (except for the voltage adjustment on the Y-sus, because it won't stay up long enough)

I have the following to report-

1. When going for the voltages to the Y-sus, the sets protection kicks in before my meter can give me an accurate reading. Following PlainBill's advice, I unplugged the power leads to the Y-sus. Now the set does not go into shutdown, and I can get a reading coming off of the main power panel to the Y-sus panel. Voltages are in spec (Va=60v, Vs=186v). This leads me to believe that there is a short of some kind on the Y-sus. I don't see any signs of damage. None of the caps look to be bulged.

2. The set will go into standby (green LED turns orange) after about 30 seconds. I assume this is normal when there are no inputs detected. I can press the power button and the LED will turn green again. If I hold the power button down for a few seconds, the LED turns orange. This seems normal to me, but I have never seen this set in operation so I'm not 100% sure.

3. Lack of sound. I read that there's a fairly common problem where the Y-sus hybrid IC dies prematurely. This would be the no picture, has sound scenario. What would cause the sound to go bad as well? Hmmmm... second thinking this, maybe the set has just never stayed on long enough to produce sound before going into shutdown. I wonder if I can get sound when the Y-sus is out and the set stays on for a while. I'll get back to you on this.

I guess my main concern is verification of the Y-sus being the culprit. I'm currently critically underfunded, so I'm trying to avoid the "replace this and then try again" methodology. If I can be more than fairly certain what need to be replaced, I can probably justify the expense.

Thanks in advance for any help you can provide.

Xwell

[Xwell]

Re: Vizio p42hdtv10a - No Picture, No Sound

OK, I found something interesting. When a continuity check on P1, it's showing a short across the ground pins and the Vs pins. I show a short to ground when I check the four Vs pins on the hybrid, as well as the four SUS_OUT pins. If I pull that IC, is there a schematic or a test plan to allow me to validate that the short is being caused by the hybrid?

[rpgruss]

Re: p42hdtv10a - No Picture, No Sound

It's your IPM, intelligent power module. I have two tvs with this exact same board combo (HP PL4260N) that have the same problem . Check the 2 fuses on the y sustain board, 1 or both may be blown. You can buy the IPM chip and install it yourself for around $30-$40, or send out for exchange for $70-ish.

Word to the wise: make sure your soldering skills are up to the task. I tried to do it myself and failed (and murdered the board in the process), the one I sent out is working like a charm. Replacement boards are also hard to come by; I ended up buying one from China for $100.

Edit - After re-reading your OP, I should clarify. Most likely the fuse is not blown if you are getting a protection mode on the power supply. Also, the IPM is the hybrid IC.

[Xwell]

Re: p42hdtv10a - No Picture, No Sound

Thanks for the info. If I do remove the IPM, can I put the Y_SUS board back in circuit to see if I can power the set up without the protection shutting it down? If so, is that a pretty good indication of the IPM being the culprit?

Thanks again!

Xwell

[rpgruss]

Re: p42hdtv10a - No Picture, No Sound

You tested for shorts on the IPM, and you found them. Per this blog post the IPM is the problem: http://blog.coppelltvrepair.com/2011...s-ipm-for.html

You can double check there are no other faults by unplugging the y sustain from the power supply and turning on the tv, it should power up fine with no picture.

[Xwell]

Re: p42hdtv10a - No Picture, No Sound

OK, I had to resort to a hacksaw blade to get the IPM off of the board... Even then, removing the pins left behind was quite a chore. It felt like these things were pressed in! Once the chip was out, I tested and found a short between the sus_out and ground pins. That's a good sign.

I've received the replacement, and before I attach this one, can anyone recommend any further tests that I can do? Rpgruss, I have powered the TV on without the Y-SUS board and it appears to power up successfully. Still no sound, and no picture (obviously). At least it doesn't power down after a few seconds!

Thanks again for all the help, and I'll let you know what happens once I get the chip back in.

[rpgruss]

Re: p42hdtv10a - No Picture, No Sound

Glad you got it out, like I said those things are a bear! Anyway, I would there are 3 or 4 MOSFETs on a heatsink near the module. Check those for shorts.

Also, you mentioned a hacksaw??? There are a few surface mount components under the module, make sure they are all intact. Other than that you should be good to go, you have a fault in the same place almost every other bad IPM does.

[Xwell]

Re: p42hdtv10a - No Picture, No Sound

Thanks, I was careful not to make contact with any of the surface mount components. I did scratch some of the enamel off of a ground pad, but I covered it with fingernail polish.

I did find a short between the +18v mounting hole and ground. Turns out it was the C29 cap next to the bank of larger caps. It was very loose, and wiggling it would make or break the short. I desoldered the inside leg and the cap came off of the board. Looks like that leg was broken. The short is gone between the +18v and gnd holes, but I am getting continuity across the legs of the cap when off of the board. Is that correct?

Also, looking at the underside of the IPM, I found the traces leading to the pins corresponding to the +18v and ground mounting holes (as shown in the photo) to be lifting off of the board. I followed the short through the diode (D3, failed diode check, so it was removed) to the IC1 chip. Not sure how that one is laid out, so I don't know if it's at fault or not.

It's been fun so far!

[PlainBill]

Re: p42hdtv10a - No Picture, No Sound

A good cap should never show a short on the 2K ohms or lower range.

PlainBill

[Xwell]

Re: p42hdtv10a - No Picture, No Sound

Update...

I got the new IPM installed, the board back in place, and BAM! the screen lights up. So I hook up a dvd player via HDMI and get video. Hmmm.. still no sound (which doesn't upset me too greatly, it's going to be used as an A/V monitor anyway), so I hook up a set of RCA cables from the DVD player to the audio inputs on the TV. Still nothing. And still not a big deal. Heck, I paid $75 for this TV, along with a Sony GPS unit (working), and a Casio digital camera (which I sold to a co-worker for.. wait for it... $75) so I don't have a lot invested. Then it hits me, let me check the audio settings. And there it is.. Speakers = OFF.

The TV has been on since 6am, and it's now after 1:30pm. What's a good burn in time? Or does it matter? Also, this thing gets HOT! The heatsink on the X and Y IPM's are 165 and 175 degrees respectively, and the smaller heatsink on the MOSFETs that rpgruss mentioned above is sitting at 165 degrees. That's with the back cover off. I read a post somewhere that someone had mounted fans on the back of the case. I have a small pile of PC power supplies with some 12 volt 80-something millimeter fans that I was thinking about mounting in the bevel at the top of the back cover. Is that going to be a waste of time? The set will eventually be placed in a wall length entertainment center, which offers little airflow as it is. I'll have to look into boring some holes to allow better airflow. Been meaning to do that anyway...

So, first of all, I'd like to apologize to the moderator for my initial posting title, the sound works great. And second (not really, just have to be nice to the mods ya know), thanks to everyone who helped get me pointed in the right direction, I really appreciate it. And I look forward to working with you on my next project, a Mitsubishi WS-65713 projection (that I do have a lot invested in, bought it new on 2003). None of the rear inputs produce any images (just the blue screen, with the input name displayed). Front inputs do produce an image, as do any of the menus. But that's for another post....

[rpgruss]

Re: p42hdtv10a - No Picture, No Sound

Glad you got it working! You are right, plasmas do run hot. Adding fans would not be a waste of time, a lot of higher end models like Panasonic have fans in them. I would mount them at the top and set them up to pull air in from the bottom, that way you are working with the natural convection these TVs have.

[Jimmy Nolins]

Re: p42hdtv10a - No Picture, No Sound

Great , Glad you tried to fix it yourself ... i opted not to fix the ipm on my set . Gonna send it out to get done . Next one i may try , i want to keep this plasma i picked up , got 2 more Plasma's coming ( smaller ones ) and 2 lcd's . On them i will give it a shot . Knwing you did it and got it buttoned up , gives me hope on my upcoming attempt.