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Old 01-15-2012, 05:38 PM   #1
leo_the_noob
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Default Vizio VP50 HDTV20A no picture no sound

I'm new to the forum and have spent the better part of 3 days trying to learn what I can about plasma TV troubleshooting and repair. I just picked up a Vizio VP50 HDTV20A 50" plasma for 50 bucks hoping I'd learn something repairing it but I opened her up yesterday and I'm starting to think I bit off more than I can chew. It's a Samsung Panel S50HW-YD02 and I've tried cycling though inputs with the Y-MAIN and X-MAIN disconnected (in turn and both together) but I'm not getting any sound. I looked at the Y-MAIN board and found a badly burned capacitor C5601 and 2 burned resistors right by the connection for the buffers. The capacitor is unreadable so hoping someone can tell me the value so I can order a replacement. I tested the buffers following a tutorial on the Coppell repair blog and concluded that they are both shorted. I've also found a swollen cap C5709 on the Y-MAIN right by the power input connector. Surprisingly there were no open fuses found on either the X or Y board.
On the other side of the board there are other issues. A 680uF capacitor right by the power input connector on the X-MAIN is burned. At the very least I'll be replacing a few components on the X and Y boards and hoping I have sound from the set after that and if I do I'll deal with the buffers. I am very much a noob at this and hoping I'll get some help along the way. I'm doing this more for the learning experience than anything else so I'm willing to stick with it as long as it takes. Has anyone worked on this set before? In your experience is there likely to be other damage besides what I've already seen and please post value of the toasted capacitor if you happen to know. Thanks. Great forum, hope to learn a lot here.
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File Type: jpg ysus.jpg (273.7 KB, 130 views)
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Old 01-15-2012, 05:58 PM   #2
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Default Re: Vizio VP50 HDTV20A no picture no sound

It would seem like there may have been a sustained overvoltage by the power supply delivered for a long time (several seconds to minutes.) Typically, the power supply should deliver around 200V on the Vs bus; to cause this damage it was probably closer to 300-400V (wild speculation on my part.)

In my experience those capacitors are typically the same throughout the board and are around 22nF. They are used to reduce EMI (electromagnetic interference) produced by the TV, I think.

I would check if the Vs voltage is in spec - the power supply may have failed too.
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Old 01-15-2012, 06:38 PM   #3
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Default Re: Vizio VP50 HDTV20A no picture no sound

OK this is a really dumb question but I am very new to this .I've read in other posts about powering the set on and checking all of the voltages on the power supply connectors. I'm assuming meter should be set to DC voltage for this? Should I connect my ground probe to the GND pin on the connector or touch it to the screws on the board standoffs? Thanks for quick reply by the way.
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Old 01-15-2012, 06:45 PM   #4
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
I'm assuming meter should be set to DC voltage for this? Should I connect my ground probe to the GND pin on the connector or touch it to the screws on the board standoffs?
Yes, DC voltage. I normally use a ground screw for my black probe.

Post a picture of your multimeter as well.
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Old 01-15-2012, 06:53 PM   #5
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
I am very much a noob at this
BTW, you should know that plasmas have very high voltages which can/will cause you and/or your multimeter some hurt/damage.
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Old 01-15-2012, 07:00 PM   #6
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Default Re: Vizio VP50 HDTV20A no picture no sound

Wow you guys are really quick on this forum! Here's my cheapo meter and a pic of my power board X and Y connectors. I see terminals maked Vs but nothing marked Va. Where can I measure that? I can check these voltages with power to tv ON and X/Y boards disconnected? I forgot to mention earlier that I do get orange light and relay click when I plug in the set and light turns green and seems to stay on for a while when I power ON.
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Old 01-15-2012, 07:10 PM   #7
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
Here's my cheapo meter
I have seen way worse. Set it to 600V and set your pushbutton switch to DC.

PS. Sometimes it helps to "jam in" the black probe to the ground screw so you use only one had to probe. Keep the other hand in the pocket. Just make sure the black probe is in their securly and it doesn't fall out possibly causing a short circuit. For stuff like this I use aligator clips.
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Old 01-15-2012, 07:24 PM   #8
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by retiredcaps View Post
BTW, you should know that plasmas have very high voltages which can/will cause you and/or your multimeter some hurt/damage.
Don't worry I'm giving this thing the respect it deserves . I just checked Vs Pin on X and Y connectors and it measures 209V DC. Sticker on panel says Vs should be 207V so I guess I'm ok there. There are also values on label for Va , Vsc, and Ve but I'm not sure where to check those. So I can assume my power board is OK then? I don't see any damaged componenents there. I realize the short in my buffers most likely is what toasted my Y-Main board because I've been reading that's pretty common with this set. Just wondering if blown cap on the X-Main is related or just coincidental. Guess I'll just replace damaged components and see if I have any sound from the TV afterwards.
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Old 01-16-2012, 09:39 AM   #9
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Default Re: Vizio VP50 HDTV20A no picture no sound

There are little test points dotted around the board for various voltages and they are labelled. The Va is generated by the power supply and so is Vs. -Vy, Vsc and Vze are all generated on the sustain boards.
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Old 01-16-2012, 02:42 PM   #10
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Default Re: Vizio VP50 HDTV20A no picture no sound

OK I checked the following voltages on the power supply board.

Vs = 209 Label states 207
Va = 63 Label states 63

I also checked the test point for 5v SB which measured 5.15v.

All of the voltage checks were done with X MAIN and Y MAIN disconnected. I noticed the power light on the front of the TV is amber when the tv is plugged in and turns green when I power the TV on . It stays green for about 25 seconds then I hear the power click off and light is amber again. There is a small board (LJ41-04220A) which I've read is a logic board. I get a 2 green LEDS(LED2000 and LED2003) that are glowing steadily while TV is powered on as well as LED2002 which is blinking. All of these LEDS shut off after 25 seconds or so. Does it seem that this is all normal? I was under the impression that I should get audio from the set with XMAIN and YMAIN disconnected but set seems to be shutting down .
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Old 01-16-2012, 02:57 PM   #11
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
Don't worry I'm giving this thing the respect it deserves .
If you are going to make adjustments, you should put electrical tape around the shaft of the screwdriver so just the tip is exposed. That way if the screwdriver slips, there is a smaller chance of shorting something out.
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Old 01-16-2012, 03:25 PM   #12
leo_the_noob
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Default Re: Vizio VP50 HDTV20A no picture no sound

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Originally Posted by retiredcaps View Post
If you are going to make adjustments, you should put electrical tape around the shaft of the screwdriver so just the tip is exposed. That way if the screwdriver slips, there is a smaller chance of shorting something out.
Thanks for the tip. I went ahead and adjusted Vs to 207. Still shutting down after about 20 seconds. Is this normal due to the XMAIN and YMAIN being disconnected. Before I disassembled the TV I tested it briefly and seem to remember the green light in front staying on but a strong burnt odor coming from the TV. I also remember seeing very brief flashes on left and right edges of the display. I'm ordering replacements for the the burned components on the XMAIN and YMAIN boards. I have an ESR meter that I've never used before today and all caps on the boards check out ok . Hope my ESR meter isn't defective.
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Old 01-16-2012, 03:36 PM   #13
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Default Re: Vizio VP50 HDTV20A no picture no sound

Some plasmas will shut down to lack of load (X-sus/Y-sus.) This is normal.
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Old 01-16-2012, 04:10 PM   #14
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Default Re: Vizio VP50 HDTV20A no picture no sound

That's good to hear. I'll go ahead with board repairs and see where I'm at after that. I have a hot air rework station and quite a bit of experience reflowing BGA chips on laptops and xboxes so I'm considering attempting the reapir of my buffer boards myself. I really have nothing to lose but time and a small investment in the IC chips. The chips on the lower buffer are marked FE 3407F 1N07942A and on the upper buffer 3407F 1N078E9A. As I understand it only the FE 3407F part matters right? I've found plenty of ebay vendors with these in stock so I'll give it a shot.
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Old 01-17-2012, 03:25 PM   #15
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Default Re: Vizio VP50 HDTV20A no picture no sound

If any one of you gentlemen has the same Samsung Y-MAIN board(LJ41-04217A) that I do then please take a look at 2nd picture at the top of this thread. There are 2 resistors there next to the burned capacitor. It's hard to make out the color bands but both look the same and appear to be connected in parallel. I disconnected one of the resistor's legs and it measured 10.6 ohms. I'm not sure if this is the correct value given it's condition. Please chime in if you have and knowledge about it.
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Old 01-19-2012, 03:43 PM   #16
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Default Re: Vizio VP50 HDTV20A no picture no sound

Update: Got some parts in the mail today and replaced damaged components on X and Y SUS Main boards. I'm now able to connect both boards without Y buffers connected and set will power on and stay on plus I now get audio when I cycle the inputs. If the set is staying on is it reasonable to assume my Y SUS board is ok? I couldn't find any shorted MOSFETS or any other bad caps on it. Just wondering because buffer IC chips are on the way from China and worried about doing all that rework on the buffers only to have my YSUS and buffers burn up after I'm through.
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Old 01-19-2012, 03:53 PM   #17
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
Update: Got some parts in the mail today and replaced damaged components on X and Y SUS Main boards. I'm now able to connect both boards without Y buffers connected and set will power on and stay on plus I now get audio when I cycle the inputs. If the set is staying on is it reasonable to assume my Y SUS board is ok? I couldn't find any shorted MOSFETS or any other bad caps on it. Just wondering because buffer IC chips are on the way from China and worried about doing all that rework on the buffers only to have my YSUS and buffers burn up after I'm through.
If you have a scope, you can check the drive waveform.

If not, you can remove any failed buffer ICs and power up the TV with them missing. You'll get black bars where the buffer ICs are missing.
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Old 01-19-2012, 04:02 PM   #18
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Default Re: Vizio VP50 HDTV20A no picture no sound

I'm out of luck on the scope. I've already removed one bad buffer IC from the upper buffer board as it was obviously toast. The others look good. I've seen the youtube videos and the Coppell TV blog explaining how to check the Samsung LJ92-01203A / LJ41-02761A and LJ92-01202A / LJ41-02760A buffers for shorts but I'm afraid this doesn't apply to my buffers. Those buffer boards have 6 ICs a piece while mine have 4. I'm suspecting the pins on the connectors may not be laid out the same way making those tests inconclusive. Hoping someone can chime in with experience testing the LJ41-05121A and 05122A buffer boards in my set. I was considering just connecting the lower buffer which looks ok to see what would happen but worried about burning something up for lack of patience waiting for a definite answer. Thanks for all the help so far by the way. It is appreciated
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Old 04-06-2012, 06:20 PM   #19
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Default Re: Vizio VP50 HDTV20A no picture no sound

Just wanted to post a follow up. It's been about 2 months since I replaced the faulty components on the X-Main and Y-Main boards as well as one shorted buffer IC on the upper buffer board. The TV has been working great and I love it. Many thanks for all of the help, this forum is an incredible resource and I've been visiting daily just to try to keep up with it all. I've since repaired a Vizio 32" LCD TV and a 26" Sanyo LCD TV and I've enjoyed every minute of it. Thanks again!Hopefully I'll soon reach a point where I've learned enough to make a contribution here.
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Old 07-15-2012, 03:58 AM   #20
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Default Re: Vizio VP50 HDTV20A no picture no sound

Quote:
Originally Posted by leo_the_noob View Post
Just wanted to post a follow up. It's been about 2 months since I replaced the faulty components on the X-Main and Y-Main boards as well as one shorted buffer IC on the upper buffer board. The TV has been working great and I love it. Many thanks for all of the help, this forum is an incredible resource and I've been visiting daily just to try to keep up with it all. I've since repaired a Vizio 32" LCD TV and a 26" Sanyo LCD TV and I've enjoyed every minute of it. Thanks again!Hopefully I'll soon reach a point where I've learned enough to make a contribution here.
Hi Leo - I'm planning on doing a similar repair to a Y buffer board - was there any particular website/video you used as a pointer for replacing the 3407F chips?
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