CurtPalme.com Home Theater Forum

mishaux · Joined: 03 Dec 2009 Posts: 36 Location: Fort Collins, CO

Hey all,

I installed this green tube about a year ago, and probably put 100 hours on it since. Two nights ago, we heard a pop and the projector powered down. I got overly optimistic and checked the blue and red first. Nope. Of course it was the green. I was wondering if anyone had any insight in to why this might have happened. Dare I put in another tube without checking some things?

Coolant was full and the bellows wren't distended. Tube was used when I put in, maybe an 8 or so, but the wear pattern only covered a sliver of the side of the screen.

Projector is dead center and maybe 10 inches further than the recommended distance for my screen size, so the raster might have been just a bit small, definitely not hanging over the edge of the tube (unless I missed something). No other indication of trouble at all.

We had used the projector for a couple of hours earlier in the day, then it was off for maybe two hours, then I turned it back on and it had been running for maybe 15 minutes when it popped.

Also, I'd love to hear any thoughts as to whom or what I need sacrifice or atone to stop having my green tubes always taking the fall when I have a shelf full of minty fresh reds and blues.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4378 Location: Phoenix

Oops

That is weird. CM Johnson here can probably hook you up with a minty green LUG at a good price. CM?

**Curt Palme** · Posted: Tue May 30, 2017 2:32 am Post subject:

This can happen. It happened.. twice.. to the same customer, with new tubes supplied by me. Go figure. The third tube has lasted, but it was frustrating to say the least. Never did figure out why two tubes died.

A few things:

1) Is the Dallas chip new?
2) Has the set ever given a 67 error code that you ignored and kept using the set?
3) Did you install the replacement CRT into the Sony housing? If so, did you put the 4 spacers between the frame and the tube?

mishaux · Joined: 03 Dec 2009 Posts: 36 Location: Fort Collins, CO

Greens have not been kind to me Sad

I got the set with a badly burned green in it and swapped it for my precious spare green with no visible wear... which developed a heater-cathode short after about 100 hours. Replaced that with this one, got maybe another 100 hours. I got the first spare out of a 1209 a local guy was parting out. This second one I got from you, but it was slightly worn, and I think I barely paid shipping for it, so I'd consider us more than square on it.

I realized when this tube popped and I briefly considered caving and getting a digital, that it has been 22 years since I have been without a CRT projector that I was either using or nursing back to health.

~ Dallas chip: Got one from you last year and replaced it before I ever powered this thing up!

~ 67 Error: I don't think so, though there is a slim chance I just never noticed it. Would I have had to do something to clear it and keep using the set, or could it have been warning me for weeks and I never looked at the back of it?

~ I did the installation, just cut the old one out, cleaned up, and glued the new one in. Was careful to get all those little mushroom shaped pins back in place.

mishaux · Joined: 03 Dec 2009 Posts: 36 Location: Fort Collins, CO

Also, thanks Tim! I saw he had listed a few recently and pinged him. We are negotiating right now Smile

I've had an eye on your edge-blending project. Looks like fun stuff Smile

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I've made a deal with him, we'll get him back up and watching movies pretty quickly.

"Fortunately, ah say, fortunately, ah keep mah feathers numbered for just such an emergency."...Foghorn Leghorn.

I have G90 spare tubes potted, tested, and ready to ship ALL the time.

The first G90 I ever got came with a busted blue tube.

I truly do not understand why G90s tend to pop tubes when no other projector does that, unless they're dropped several feet
while still in the crate. (Which Curt knows about, having had that happen to one he bought once!)

I actually find myself wondering if the smaller heatsinked area of the G90 tube frame, as compared to the heatsink area of other
tube hardware, might not be a factor. It may be that the G90 tube runs hotter because of it.

In general I do recommend that G90 owners would do themselves a favor by taking the contrast down a few points. It keeps the tube cooler, improves tube life, and you'll soon get used to the slight reduction in brightness.

km987654 · Posted: Tue May 30, 2017 5:20 am Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Like I said in the other thread, Curt has seen this at least twice in G90s. It's happened in one of my own units once. And now there's this one. That's four known cases not counting what anyone else may have seen.

I'll bet Craig Rounds has seen it!

I think that G90s get run harder than any other projector because their focus magnetics are so good that you can run the tubes
really hard and still get great sharpness. But the harder you run the tubes, the hotter they run.

And the G90's tube frame with heatsink has LESS heatsink area than any other LC tube assembly I'm familiar with, and I'm familiar with them ALL. I've replaced tubes in every kind of LC hardware you've ever seen and several you have not. EIS, Barco 04045, Skylight I, Skylight II, Suprapan, ESCP 2000, AMC, Barco MRP, 909, G90, Marquee, you name it. Of all of them, the G90 frame has the smallest effective heatsink area and that's in a projector that is most likely to run tubes hotter than any other.

I also have the tube spec documents from the manufacturer. They define the cooling requirements among other things.

It is possible to run a tube at a temperature above 200 degrees on the faceplate. But tube life will be short!

**Curt Palme** · Posted: Tue May 30, 2017 1:34 pm Post subject:

All brands of sets have done it, the worst were the old analog Barco 9" sets that turned on the 34Kv without ramping it up slowly as later Barcos did. That killed more tubes by cracking than anything.

It sounds like you installed the replacement tubes correctly. The error 67 would shut the set down. NECs tend to have a V chip fail, where the raster shoots way off the tube, and the electron beam hits the bell of the tube, right at the yoke, overheats and snaps it. I don't think Sonys do that. The bad thing about the NECs is that when the V shift goes way off screen, it does not come up with an error message. A poor design for sure.

I don't have any other explanations for you, sorry!

mishaux · Joined: 03 Dec 2009 Posts: 36 Location: Fort Collins, CO

Ok, no worries! Sounds like I have the obvious bases covered, so I'll just bolt in a replacement and hope for the best. As always, I REALLY appreciate all your insight gentlemen!

I'm running at 68 on the contrast, not sure if that is considered pushing it or not. I worked hard on light control so I could be gentle with tubes. Do you guys have a limits you aim for?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I recommend setting the contrast no higher than you need to really enjoy the picture. Only way to find out is to experiment.

But a contrast level of 80 or more is, at least to my eye, excessive. That trades tube life for a brighter picture.

Your green tube has obviously been replaced before. With one originally provided by Barco, so sayeth the label.

Barco must have bought tens of thousands of tubes from Panasonic for their refurb business. I still regularly encounter Barco overlabelled tubes made by Panasonic before Panasonic changed their label design.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4378 Location: Phoenix

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

Meanwhile mishaux, you gonna hold an open showing for local people once you get it running again?? I'll bring beer... Very Happy

**kal** · Posted: Wed May 31, 2017 2:34 am Post subject:

km987654 · Posted: Wed May 31, 2017 2:54 am Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

All my G90s have been checked, and while I don't have a light meter, I would say that, SUBJECTIVELY speaking, if they're all at a given contrast setting, they're all putting out a similar amount of light. There is some variation but not much.

I personally think that they're all driving the tubes pretty hard with the contrast level at 80. It's more than I'd recommend.

Although I seriously do want to get my hands on a good light meter, I don't know when I'll be able to do it as circumstances have
forced me to move more quickly to buy another car than I had intended to. So I've got a brand new 2017 Toyota Camry in the driveway now, which has knocked back my funds for other discretionary spending, and to no small degree.

I was faced with a thousand dollar car repair on my last car, and I was just TIRED of endlessly spending money to keep that piece of unreliable, high maintenance Cadillac trash on the road. With a 120,000 mile extended bumper-to-bumper warranty on the new Camry, I think I'm about done paying for car repairs for several years to come. So I'll be able to replenish the toy fund. In time.

hal · Joined: 28 Nov 2012 Posts: 100

What? You bought a Camry..

I thought you were buying a 996/996Turbo (smile)

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'd love to. But any in good condition are outside my affordability range for the time being.

Not all dreams come true as quickly as you would like.

But at least the Camry is truly new. And it's a good car that should be trouble free for years.

mishaux · Joined: 03 Dec 2009 Posts: 36 Location: Fort Collins, CO

"I'll bring beer..." ~ YES! Will plan showings for beer!! The old tube is in transit to cmjohnson, should be back in business in a week or two. I'll keep you posted!

"contrast values between projectors are somewhat meaningless" ~ That makes perfect sense. I think I have always basically run the contrast up until I can hear the projector starting to work hard (louder raster noise, blooming, etc), and then backed it off a good margin, like 20% ish. I ran my old 808 for a few thousand hours over a decade or so without any noticeable tube wear, so it worked as a rule of thumb for that set. I doubt that says TOO much about the G90 I suppose.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

G90s are a bit different, though, because their focus systems are so good that you can run the contrast up to 100 and not have any blooming worth mentioning, but you're hitting the tubes REALLY hard. It's why G90s are known to burn tubes faster than any other 9" projector other than raster/calligraphic projectors, which are used only for flight simulators.

Interestingly, the spec on the LUG tube is that the phosphor screen is rated for a maximum dissipation of 29 watts. If the tube
is driven harder than that, it'll exceed its thermal rating and heat related failure becomes quite possible.