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Discussion Starter · #1 ·
I was not meant to have a G70. God hates me. It's long but here is the deal….


On a gamble I buy two G70 projectors – problems other than bad tubes unknown.


I get the first projector, has burned tubes and loose connector. Clean looks like very few hours.


I get the second projector just has burned tubes. Has more hours on it than first one.


I send tubes from first projector to VDC for rebuild.


Get them back, install and all is well for a few weeks.


Pop! Arc sound from somewhere and now the ‘C’ board on my green tube has problems. Notice spots after switching board with 2nd projector.


Send Blue and Green tubes back to VDC because of little spots. Charlie sends back two more.


I install the new tubes, turn on the projector, sizzle spark sizzle – there is a little spot missing silicon on green anode and it is arcing to the chassis. I call VDC and ask about the silicone, get some from a local video shop and re-silicone the green, let it set up over night and it seems to work. My keystone is off but I’ll deal with that later I say to myself.


I let the new tubes run at 0 brightness and 0 contrast for a day.


After giving the tubes some easy warm up time I turn the contrast up a little, the blue crt display starts to shake and I can hear a noise coming from the power supply. If I turn the contrast back down it goes away and the blue is ok.


I call VDC again about the blue and Charlie told me to make sure the connections on the anode lead is clean. I check it and is seems clean. I asked about the anode connection on the CRT itself and Charlie says it’s not likely the problem but if I’d like to remove and check it might be. I scrape the silicone off and remove the anode. There is silicone in hole and all over the metal clip that snaps into the CRT. I clean it all up and re-silicone it making sure not to get any silicone on the connection. Let it set up overnight, re-install it and amazingly it works just fine… So I thought.


My keystone problem from when the green tube arced is not adjustable. The numbers change but the display does not. I pulled the ‘B’ board out of my second projector and swapped and it works… So I thought…


I run the projector on the floor for a week or so and all is great. Damn I like the look of a G70… I buy a ceiling mount, cut up my ceiling, get the neighbors to help me lift it up just in time to watch the final game of the NCAA tournament. Neighbors love the HDTV and big screen even with a 20 minute alignment.


Over the next couple of weeks I worked on the alignment. The picture is good, HDTV and DVD through the HTPC looks great!


Easter Sunday comes along I figure I’ll put in a few hours on the focus – focus was good but not consistent so a full white screen had slight yellow areas here and there. I play around for a few hours and finally decide I am set. I finish the alignment for the day.


I watch HDTV for a while, and then I start watching my good ol’ Fleetwood Mac DVD. About half way through the DVD I hear kind of dull pop sound and the projector and it goes off. The display says error 36. Before I even lookup what 36 is I take the outside cover off, take the screws off so I can get to the boards again and then I see it. After I said a few words I had to look again. I then said a few more words and looked again. The blue tube is busted and the deflection coil, EM focus and the ‘C’ board are just hanging down by the wires. How the hell could that be? The tube broke just underneath deflection coil. How can this happen?


I disconnect everything going to the blue tube and figure while I’m still in shock I’ll see if anything else is wrong. I power up the projector and starts to come up – shuts down with error 36. I start swapping boards with the other G70. I thought the problem would be on the ‘E’ board but it doesn’t change so I try a couple of other easy swap boards but no go. I just turned it off and came upstairs. It was either that or just unbolt it from the ceiling and let it drop to the floor…


Anyone need any G70 parts? God knows I wasn’t meant to have one. Now I have two non-functioning projectors that I have spent close to $5000 on. Best part is I have a new Blue CRT with maybe 30 hours on it that just happens to be in two pieces.


Why me?
 

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Brutal!


All I can suggest is that_perhaps_ you've had HV that has been too high all along that's been causing the arcing. For a tube to snap in half without physical abuse, that's usualyu what it's pegged to.


Not that this info helps you any, but you might want to check that or even drop in the worn tube that I think you still have off the other set...


I have not yet worked with VDC G 70 tubes, so that may be the problem as well..

Curt
 

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Guys!


The likelihood is that if the tube shattered during operation it would have wiped out the high voltage power supply as well, due to a hige arc when the vacuum went.
 

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Discussion Starter · #4 ·
Well, the 'E' board is bad for sure and most likely the HV power supply - I haven't removed the HV stuff - it is still on the ceiling. I'll have to have some help getting the thing down. I did try the other boards in the other projector and they seem to be ok.


So far out of the two projectors I have these bad parts:


One set of worn Red, Green, Blue Tubes

Blue Tube with very few hours (Currently in two pieces for easy shipping)

'C' Board

'E' Board

Something in the HV.


NEC is looking good. Which one should I get Curt?
 

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Mike, Holy shi*! All this happened after you asked about focus today? Good grief! What a day you have had! I s there anything I can do to help out? Other than providing the beer for you to cry in probably not much I can do. I would suggest that you send both pj's to Eric Lang or Terry Ferrentenois for repair. AVFORSALE in Atlanta has a G70 ATA case on ebay right now for $149. The big question is do you sink more money in or start over with something else. Too bad someone is not in your area to make a technical analysis for you. Let us know what you decide to do. I will say a few choice 4 letter words for your pain.
 

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Mike, Hangover? Are you still with the living? Hellooo...
 

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Erratic critical safety caps and other deflection circuitry components can cause excessive horz deflection current in a yoke. The yoke can heat up rapidly to the point that the crt neck cracks. Popping/arcing could have

been symptomatic of the same failure(s).


The diagnosis and repair would probably be a headache even for a

professional. And you would sure want a good guarantee on the repair.
 

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I have another theory to offer on the broken B CRT.

Some time back Guy Kou has an instance where one of his CRT's broke while the unit was in operation. As I recall he was convinced that the cause of this was running the picture to close to the edge of the CRT face, which in turn was causing the electron beam to heat up the neck of the CRT where it bells out, and then finally a failure.

The NEC guy had the failure on was an XG135LC (I think) which uses the same CRT's as the G-70 (MEC P16's) with some slight differences. These CRT's have very narrow necks.

Personally I have not seen this before on an XG or a G-70, but did have a Barco 1208 come in one time that may have had a failure based on this.

I also believethat there is something to be learned from all this. The concept of putting your projector significantly closer to the screen may be a good thing for some projectors (ie the G-90) but I am not sure that the gain outweighs the risk with other models. This possile failure, the risk of overheating SDK chips and convergence circuitry and dconvergence drift are possible outcomes.

Oh well, my ramblings.


Terry
 

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Shoot me an email to the address below. We might be able to swing a trade of some sort...


Curt
 

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Discussion Starter · #10 ·
Well, I got up this morning hoping that yesterday was all just a nightmare but no it really did happen. Dennis, I would have to sober up to have a hangover right? I'll try and not let that happen any time soon....


In talking with several people I guess it comes down to 2 possibilities.


1) A problem with something in the deflection circuits that would cause the yokes to heat up and snap the tube where the coils touch the glass. As I took the blue pieces out the coil was rather hot. I didn't think much about it because I felt the others and they were equally hot. I am checking into how hot they get under working conditions with my worn tube G70.


2) A bone head move on my part. It is possible that after I moved the projector to the ceiling I moved the blue raster close to the edge as in what Terry said. I was running the projector about 2" closer to the screen than what it was supposed to be - I have floor joist problem..


I don't see how it could be the tube itself. I am going to call VDC and see what Charlie thinks - He has done so many tubes he may have seen this before. I may ask him about moving the new face and gun to my worn blue tube (maybe not worth it or possible).


I really appreciate the input both by email and here. Nothing worse than having such a great picture just to see go up in smoke (and broken glass).


Thanks!


-Mike
 

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Discussion Starter · #11 ·
I just talked to Charlie from VDC - great, helpful guy - I posted pictures of my busted tube and he pointed out where the break started, an arc from the inside of the tube out to the coils on the yoke. He said he has seen a lot of this and for some reason it happens on the blue tubes most often. I'll have to make sure the projector is fixed before I put another tube in it. (not too difficult since all of the possible causes went up in smoke)


Before I pulled the tube out I called and he said depending on the break he may be able to fix it! Can you believe he can weld a new neck on a tube? That amazes me! After I got it out and took the pictures he said that the crack up the shoulder means he wouldn't be able to just put a new neck on it. I'm even unlucky on that!


The yokes shouldn't be as hot as they were when I pulled it down, there was a little white sticker that had turned brown it had been so hot. I guess I'm still back to what caused the initial problem - the deflection board or my stupidity of not rechecking the centering of the raster after I moved it up to the ceiling.


I guess it doesn't make much difference - if the deflection board had problems and heated up the yoke and tube arced and broke or if there was a high voltage problem... the tube, deflection board, and the hi voltage are shot now! You can bet I'll double check the center when I get it going again.


I'll let you know how it all turns out, thanks for the input and thanks especially to Charlie at VDC for taking the time to get me watching TV again!


-Mike


btw - if you want to see my pain you can go to here and see the pictures of my broken life. The little white spot above the blue dot in picture 3 is where the arc popped the tube.
 

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Mike, I feel your pain. The blue tube this time!? Was it not the green tube that the arc took out the deflection yoke coil the first time? I am getting real gun shy on mine now that you have had this happen with similar chronology of events as a I had on my blue tube. I am still waiting on the new (used) deflection yoke to arrive from Eric to try and get the sizing from max on the blue. Other than that the image looks great and no problems since I replaced the C block. In view of what you have gone through with your projector presenting similar symptoms as mine until the final death throws over the weekend, I am seriously considering sending mine to whoever is qualified to deal with this. Personally, I do not think Eric's service department is any more qualified to work on these in depth beyond swapping boards to see if a problem goes away. Don't get me wrong, I have the deepest respect for Eric and his staff from a professional business point of view. I just question his technician's familiarity with Sony projectors on a component level. Please forgive me if this assumption is incorrect. He bailed my ass out with a used C block when there where none to be found anywhere else but Sony for $1200. Who are you going to send this to if you go that direction?
 

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Mike. 2" closer shouldn't have made that much difference. It all depends on where your H size for RGB ended up and the raster centering that's in question here.


Terry
 

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Quote:
Can you believe he can weld a new neck on a tube?
It shouldn't surprise you, because this process is done for every tube the VDC rebuilds.


The first step is to score the neck roughly 2" or so from where the flair starts at the bell of the crt.


Then the old neck and electron gun are removed at the score and a new neck is attached by melting the glass of the tube and the new neck.


The new neck is shaped kinda like a test tube so that the new gun can be slid in without damage.


There is much more to the process, but I actually got to watch one of VDC's craftsmen performing the process of attaching the new neck.


After my tour of the plant, I have come to believe that Charlie and his craftsmen can do just about anything to a CRT.


Vern
 

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Wow Mike. I just want to add my name to the list. I know how my heart sinks every time I hear even a strange noise in my pj. I can't even imagine what went through your mind when that happened! Stomach in your shoes? Here's to getting back up and running in the shortest time possible!
 

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Discussion Starter · #16 ·
I have more info that I can’t understand. After doing some basic checks on the ‘E’ board – Q7 & Q8 are shorted; the parts from Sony are $129.62 each. I haven’t thoroughly checked everything else on the board, could be other problems that would just blow the hell out of the $260 worth of parts. I took a gamble on testing the other boards and power supply in the other semi-working projector. All the other boards seemed ok so I put the ‘E’ board from the semi-working projector into the re-tubed one with my worn blue tube. I said a little prayer and turned it on… It didn’t blow up so I guess my gamble paid off for once.


I let the projector run for a few minutes then shut it down to check how hot the yoke was getting. The blue (old original tube) was just slightly warm. The rebuilt green was not hot but definitely a lot hotter. The rebuilt red was about the same as the green. I powered the projector up and let it run about 15 minutes and checked again. The original blue was a little warmer than before but not hot. The green and red were way to hot to keep your hand on!


I then took out the rebuilt green and put in an original worn green. After letting everything cool down I tried again. Now the original green and blue just get warm but the red is way to hot.


How is it possible that a yoke around the tube can be different temperatures on original vs a rebuild? There is no electrical connection! I just don’t understand it.


I called Charlie at VDC and is was surprised and says he doesn’t have any idea why that would be the case. He has even offered to just give me my money back.


I then called Eric at projection systems and he had not heard of that either.


What do you think? How do I get myself into these things?


-Mike


P.S. I am also looking for a used ‘E’ board. I checked with Eric – he was going to check and call me back but never did, I guess that means he doesn’t have one. Do you have any source for used parts for these things?
 

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Mike, I know Eric has a few G70's he is scavenging parts off of because I have been buying them. When you call go to the sales dept. I think it is Mike that will answer. He will take your order and give you a better price. I bought another G70 today with a much higher serial number than my first. 1465 units newer in the production run. I am going to retube this one with Sony tubes to see if there is a difference. The deflection yokes on all of my tubes run cool to the touch. At least I think they do because I have never felt any heat around any of the CRT neck areas while adjusting the yokes and magnets after the projector has been on for hours. Just out of curiosity if the projector was set for 220v instead of 120v would it fire up? And if it did would it run hot? Just a thought.
 

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Discussion Starter · #18 ·
Hey Dennis, you must have a sever case of projectitis! Another one? You sir are a brave brave man!


Did you get the first one all setup and running? What are you driving it with? My rebuilts really heat up when I run a Tripled or Quadrupled signal into it. I only leave it running for just a few minutes to check it out...


Tomorrow I'm going to move the rebuilts to the other chassis and see how that goes.


I'll call Projection Systems back and ask for sales.


Thanks and yes I'll have another beer,


-Mike
 

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Discussion Starter · #19 ·
Hey Dennis, you must have a sever case of projectitis! Another one? You sir are a brave brave man!


Did you get the first one all setup and running? What are you driving it with? My rebuilts really heat up when I run a Tripled or Quadrupled signal into it. I only leave it running for just a few minutes to check it out...


Tomorrow I'm going to move the rebuilts to the other chassis and see how that goes.


I'll call Projection Systems back and ask for sales.


Thanks and yes I'll have another beer,


-Mike
 

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Discussion Starter · #20 ·
Ok here is the latest…


I re-assembled the second G70 (the one on the floor) using old worn blue and red with a VDC green.


I reset all inputs to the ‘factory’ settings.


I connect a vcr to the composite input and check the raster on all three tubes – the raster is no where near the edges of the phosphor. I then disconnected the video input so the projector is on the ‘video’ input with

nothing connected.


After letting the projector run (with no input) for about 20 minutes I feel around each yoke. The red and blue are warm to the touch, the green is approaching hot…


I then connect the video again and let it run for about 20 minutes again.


Then I check the yokes again – red and blue are a little warmer than before but the green is just plain hot. It is not melting heat and its not hot enough that I can’t hold on but it is hot.


After letting everything cool down for about an hour I repeated the process a second this time resetting the projector to ‘initial’ settings on all inputs. Same result.


I then input an RGB signal at a fairly high resolution and refresh – 1440x960 at 72hz to be specific.


I only let it run for about 10 minutes because it heats up much faster and much hotter at these higher rates. The red and blue are warmer but still not hot – the green is just about to the point that I can't hold on to it.


It is not the coils themselves that get hot it is the ferrite the coils wrap around.


I guess I am back to square one….


If someone could run their G70 for a while and then check how hot the ferrite in the yokes around the tubes get I would be forever in your debt! Especially if someone has a VDC tube and an original to compare the heat to.


I think I was meant to watch a 14" black and white TV from 1966.


Thanks much!


-Mike
 
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