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Discussion Starter · #1 · (Edited)
I was watching a baseball game in HD on my Mitsubishi VS-50805 last night when suddenly the picture went black. Still had audio but no picture. When I pressed the 'MENU' button on the remote I got this lovely display:


I tried the usual tricks like turning the set off for several hours but saw the same thing when I turned it back on. I get this same symptom on all inputs. I suppose this could be a convergence problem, a massive one that affects all colors, or a mechanical problem like a bracket breaking or something in the optics path moving. The thing that's strange is that the picture video is gone but the menu graphics still work. Any suggestions on where to start?

Thanks,
JVP
 

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Your image indicates a convergence problem. The fact that you lost video at the same time is unusual for a convergence failure. What is common on this set is for coolant to leak onto the circuit boards from the CRT. It is very important for a coolant leak to be handled properly for a reliable repair. The location of any coolant on the board(s) needs to be mapped carefully and the boards removed and cleaned carefully to not expand the problem. It is best to find a tech that has done lots of these to do the job, though in many cases it is possible to DIY.

Look carefully for wet spots on the metal frame corners on the crts and on the boards. Use the markings on the sides of the boards to map the locations as coordinates BEFORE the boards are removed.
 
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Discussion Starter · #3 ·
I popped the back off the set and inspected the CRT brackets, circuit boards, screws, springs, etc. and found no evidence of a coolant leak. I paid particular attention to the three CRT brackets and the little holes at their corners. I used a mirror to inspect the area behind the big heatsink. I saw nothing that was either liquid or looked like dried residue. I did see those Sanyo audio amp modules clipped to the back of the heatsink, the board looked clean around them.

Any other thoughts? I don't have a a service manual, where can I get one?
 

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Do not assume that you have not had a leak. The common form of this problem is a transient leak, just enough to releive a little pressure in the coolant chamber, then the coolant migrates very completely, leaving little trace other than corrosion. The corrosion is not due to the coolant itself but from moisture in the air that is absorbed over time by the fluid. It is very possible that a few drops left no trace on the brackets, dripped to the board, sat there a long while until there was enough water and debris absorbed to become conductive. The solution then eats out the feed through connectors between the sides of the signal board, or the legs of components, or the connectors between the boards. You have to inspect very carefully to find the problems sometimes if the coolant has migrated away to the particle board below the chassis. Lift the chassis slightly and look for spots there.

The manual should be available from Mitsubishi parts. It may be available from some online vendors, but they are not authorized to sell them by Mitsubishi, so there is no telling what you will get.
 
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Discussion Starter · #5 ·
Good/Bad news! I couldn't find evidence of a coolant leak and wasn't comfortable ripping into the set, so I called a TV repair service. Their tech came out popped open the front of the TV (why didn't I think of that?) and pointed directly at a spot under the blue tube on the right side of the set. There was evidence of a sizable lake there that had since dried up. I was so impressed I took a very high resolution image of it:


The "RE" connector on the green board appears to be completely surrounded by the discoloration. If you zoom in on the image you can see some vias that are discolored in that region of the the RE connector. What's not as obvious is the damage on the tan PWB on the left. If you look at connector "PE" that mates with "RE" you can see some green fuzz on the pins, and some more on the jumpers to the left of it. There are bits of residue elsewhere as well.

The tech told me that their firm will only replace these boards, they will not rework them. He also told me that the boards are difficult to come by (and later verified that he couldn't get either of them for me). One other interesting note, he said that the blue tube is particularly susceptible to leakage because it runs hotter due to the higher opacity of the blue filter.

Anyway, since replacements are apparently not available, I've got nothing to lose in trying to fix this thing myself. I've done a lot of work on multilayer PWBs, but I do have a couple of questions on how to get into this thing:

1. Do I go in there and disconnect all the external connections (around a dozen) to the entire chassis and slide it out, or is there some way of getting just the boards out that I need to work on?

2. How do those board to board connectors work? I noticed when I looked at the picture at 100% resolution that the "RE" connector that most of the top of that connector comes off. Does it pop out entirely or does it open like a door? They don't seem to open easily - is there a technique or tool required?

Any advice is appreciated. Also, feel free to snag that picture and use it as you see fit. I might have found that stuff earlier if I had seen such a picture.

Thanks,
JVP
 

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Lots of shops don't want to take the risk of fixing these, because if you are not thorough, it is easy to miss something. If you don't do it very carefully, you can have lots of issues down the road. Frankly, the fact that you could miss this leak indicates that you may not be a good candidate to repair it, but as you said, you have little to lose.

Do EXACTLY as I describe. Note the numbers and letters around the edge of the boards. Use these as coordinates to make careful notes and a map of the areas and components affected. On the green board(signal board), you MUST consider the feed-through holes components that need to be tested and repaired. These are the source of most problems that people miss when repairing these boards.

After mapping the area of the leak as well as you can, pull the chassis. Yes, disconnect all of the connectors and pull it out. Then you can remove the boards from the frame more easily. The white connecotrs just snap up. Pull evenly on the two tabs on each side, straight up. After removing them, go over the boards very carefully and verify your map of the affected area. Pictures are very helpful to refer back to. Then you want to gently brush or scrape the corrosion off of the components and scrape back any traces that are darkened to the bare copper(remove the green coating). To do this I use an angled blade and a pick and a fiberglass brush. A stiff tooth brush can work oK as well. Washthe boards in isopropanol or denatured alcohol as you are brushing the leads, connectors and components to get the corrosion and goo off. Once corroded areas are clean down to the metal, let the board dry. If there is a white residue, just brush it off when completely dry. Handle the boards carefully.

Now repace any components with corroded legs and repair any connections or traces that are corroded through and/or lack continuity. You have to check each and every feed-through hole on the signal board for continuity in the area that had coolant. Depending on how long the coolant was there, you may have none that are bad or you may have many. If you find one that is not continous, scrape back the coating to the metal on each side, take a strand of copper wire and feed it through the hole, then solder it on both sides.

After repairing the boards, run them through the dishwasher. Yes you read correctly. This is a trick that I learned from an engineer from Tektronix, the test equipment manufacturer. Use regular dishwasher detergent and a dry cycle. Stand the boards on edge so the water drains and it dries better and be sure that they are supported well.

If you have repaired all of the connections and components damaged by the coolant, you will have a high probability of a fix. If the set does not work properly at that point, there may be some component damaged by a short,but this is rare. It usually means that you missed something or damaged something in handling, so be thorough and careful. Put the boards back in after they have dried thoroughly, as water and solvent can hide under the chips. This is why the dry cycle on the dishwasher is important. If you don't have one, dry the boards in the sun for a day. Berfore you reinstall, be sure to clean off the frame and clean any coolant from any wires or from the CRT brackets. Add a gutter under the tubes to divert any future leaks. I use an angled vinyl siding cut to fit the width of the chassis. If the tube keeps leaking it can be resealed, but this is not typical.

If you still have problems and need to do any troubleshooting, you will likely need a scope and a service manual, along with troubleshooting skills and circuit knowledge.

Good luck. Be very careful and very thorough. Do not force any connectors. If you break them or break the boards, you are unlikely to find replacements.
 
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Discussion Starter · #7 ·
Great news! I yanked the chassis, and found a jumper that had been corroded down to a thin filament. Also found some spongy green scuz that, if conductive, was shorting two wires together. I buzzed out all the board to board connections with a low-current ohmmeter and found them to be in good shape. I checked several vias on the double-sided board and found those all to be fine as well. I wonder if some of what appeared to be a large area of previously-wet board was something left over from manufacturing, perhaps a final cleaning process. The real problem turned out to be on the center single-sided board in this area right behind the "jungle" plug-in board:

I cleaned up that green stuff and replaced the severely corroded jumper (obscured by the jungle board in this image). I slapped the chassis back into the set and it fired up and it is working fine. Now I've go to get some vinyl siding to make a drip tray.

I'm glad I didn't have to buy a new TV. I was out looking at LCD and plasma HD TVs this past week and was not impressed with what I saw. The high-speed update that these new screens have really brings out the "blocky" encoding artifacts in the MPEG images, particularly at scene changes and in scenes with a lot of motion in them. There is some new technology just now appearing in very high-end screens that cleans up a lot of those artifacts. I hope the old Mitsubishi can hang on for a couple more years until that post-processing technology makes its way into the mid-range (~$2,000) 47" screens.

Leonard, thanks for your advice. You saved me a bundle of money. Can I mail you a beer?

Thanks,
Jim
 
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Discussion Starter · #8 · (Edited)
Hi,
I too have this unit VS-50805 and have enjoyed it for 7 years. Suddenly, while watching tv 2 days ago, all picture went black. Confirmed for all inputs. No video at all - just black. No menu screen, nothing. Audio continues to work well for all inputs.

After reading this (and many other posts on many boards) I am stunned by the design flaw in these TVs. CRT leaking oil directly to the circuit board is very poor design. So, while my symptoms are different from the (convergence) issue above, I took a peak inside the tv to find similar horror - dried up lake from the blue CRT and moist lake from the green CRT. (Several other images available in hi-res as well if helpful)






I visually inspected the top half of the board in the 'splash zones' and couldn't see anything obvious that was corroded or needed replacement. I then took a look at the bottom to notice further horror. Many of the bottom vias were corroded. I cleaned them according to the procedure listed above (minus the dishwasher -- just scraped, brushed, and cleaned with isopropyl alcohol). Photos of the bottom view available if helpful.

My question is: for a complete picture blackout, is there a portion of the system which may be culprit as the starting point for investigation? Is there a fuse that controls the CRT that may have blown? What are the recommended next steps or areas to narrow down the search?

With CRT coolant leaking out, is there danger of the tubes overheating? Is it recommended to have them replaced once this mess is all corrected?

Additionally, this terrible design has undoubtedly caused many people a lot of expense in repairs or replacement. I am quite surprised by this common problem. I am considering initiating class-action lawsuit against Mitsubishi for owners of all these models. Has this already been done to anyone's knowledge?

Thanks for pointing me in the right direction for next steps. I really want to make this beast live again.
 

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Class action lawsuits are usually counterproductive. Mitsubishi extended warranties on these problems on a case by case basis for may years. I had sets as old as 5 years with repairs paid for by Mitsubishi, or some accomodation made on the pruchase of a new product. I doubt that they would do anything on a 7 year old set, but you could ask.

As for the repair, you have to be very careful and diligent to get it right. You must map the area that has had coolant on the board and verify every connection in that area, after washing the board in solvent. Additionally, at this age many of the capacitors should be checked for high ESR.
 

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After looking at the pictures, I suspect that what you see on the power board is not coolan, but silicone that came from the heat sink compound on the convergence ICs. Also, the other area are not where the leaks usually land. Was the set moved on its side or back? The coolant usually leaves significant corrosion if it has been present for very long, but I don't see any. Is there more to the story?
 
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Discussion Starter · #11 ·
The set was on its side twice during moving each time (flat on the front) several years ago. Has been working great at this location for the past 3 years, and just cut out 4 or 5 days ago.

The only corrosion I could see was on the bottom of the boards. I have many photos of that if that is somewhat helpful please let me know and I can post. Many of the bottom pins had build up on them which were scraped and cleaned.

When I opened the back of the unit, all 3 crts had obviously been leaking. I say this because the black tape on the back of the housings was all oily, and the power lines coming in to the lights also had wet liquid which I was able to wipe down.

For a black out such as this, is there a fuse that controls power to the CRTs that may have blown out spontaneously? The error code result on the front of the unit is 1-2. It only seems that the picture does not come on. Not a specific problem of visual convergence like the picture at the top of this thread....no picture at all. :-(
 

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1-2 indicates that there was no shutdown. There is no fuse on the CRTs. The only way to repair a set with a coolant leak is to remove the boards, clean them thoroughly, repair corroded connections, broken traces, and check every feed-though on the double sided signal board. Then you can troubleshoot the remaining problems if you have the skills and equipment. Read post 6 above.
 
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Discussion Starter · #13 ·
So, after 2-3 weeks of having the tv off, after having opened up the guts of the beast and cleaned things as best I could through visual inspection, we turned the TV on. Slowly by slowly the picture started returning, though very narrowly in the from the middle, and widening vertically. Almost normal except for a bowed picture. I entered the secret service menu as outlined in the service manual, made some configuration changes and ultimately performed the reset. I had to then readjust all the alignment for reds and blues through the standard menu, and our baby is back to performing well. We have a thin disturbance line up along the top of some tv channels and vpos changes doesn't seem to affect the picture.

Anyway, this is good enough for us to be almost back to normal. Likely the leaking affected the ICs on the signal board. Now I need to build the drip guard and hope that this thing lasts long enough (2-3 months) for me to donate this and buy a new flat panel LCD.

Last question remains: is this unit 'safe' to use with so much CRT coolant having leaked out?
 

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So, after 2-3 weeks of having the tv off, after having opened up the guts of the beast and cleaned things as best I could through visual inspection, we turned the TV on. Slowly by slowly the picture started returning, though very narrowly in the from the middle, and widening vertically. Almost normal except for a bowed picture. I entered the secret service menu as outlined in the service manual, made some configuration changes and ultimately performed the reset. I had to then readjust all the alignment for reds and blues through the standard menu, and our baby is back to performing well. We have a thin disturbance line up along the top of some tv channels and vpos changes doesn't seem to affect the picture.

Anyway, this is good enough for us to be almost back to normal. Likely the leaking affected the ICs on the signal board. Now I need to build the drip guard and hope that this thing lasts long enough (2-3 months) for me to donate this and buy a new flat panel LCD.

Last question remains: is this unit 'safe' to use with so much CRT coolant having leaked out?
I doubt that enough coolant leaked out to cause a problem, but it is easy to check. If you look into the lenses with a flashlight and see a bubble, you need to add coolant. There is not much problem if the bubble is smal other than you may see it in the pix, but if the bubble is large enough it might result in some uneven cooling of the face of the CRT and potential cracks in the glass. Not likely but it is a risk.

How did you clean the fluid? If you did not wash it thoroughly the corrosion will likely continue and you may have problems in the future.
 
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