CurtPalme.com Home Theater Forum

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

I'm not saying I can't solve this one. It's just a frankly BIZARRE problem and stuff like this is fun to troubleshoot.

Projector is a 2005 VDC Marquee Ultra. It still has some Electrohome marked boards in it, like the main board.

This one has about 10K total hours on it or so sayeth its clock.

Green is normal except for a streaky neck card. Green tube is a P19LCP type.

Red isn't red. It's green, a P19LUG. That it's green and not red is irrelevant. It got this way due to an error on the
part of the last guy to work on it. That's OK, I have reds to swap into it when the time comes. But this (green) red works fine.

Blue....dead, dark, no picture, no raster, no output.

Observation: Blue has a VDC redesigned neck card on it. Red and green (well, both greens) have the regular card types, one for LCPs and one with pin 6 connected to G2 for a LUG tube.

All VIM outputs confirmed as being working by individually swapping them to the (center) green neck card and tube.

A known good neck card is connected to the blue tube. Still no picture.

UNLESS....the G2 lead is unplugged. This results in a bright raster but no other picture elements, not even by cycling through the Marquee's internal test patterns.

One more piece of the puzzle:

The later model VDC designed neck card was VERY HOT when I first removed it from the CRT. ALMOST hot enough to burn me.

I do NOT know how hot those cards normally run.

The other cards run only warm. Which is typical in my experience.

I was wondering if the blue tube might be a P14 filament voltage problem victim. But if that were the case, you would not
be able to get a bright raster out of it even with an uncontrolled and ungrounded G2 pin.

What are the odds that the blue tube could be bad in such a way as to cause these symptoms?

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Guys

I was told not to mix and match old and new neckboard types. I am thinking also about a cathode to heater short.

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

The neck board found on it is the version that VDC says CAN be mixed and matched with older cards. There is a different version of the new neck card which is NOT compatible with the older cards, but this particular card is not one of those.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Hey

Are pins two and six shorted together on that neckboard? That might explain the weirdness.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Guys

I need to test several picture tubes a month, and pulling a tube out of my test projector just isn't Fun. I took a spare LC lower mounting plate and drilled it to take two flathead allen bolts to attach the plate to the top of the green tube.

The plate lets me secure the tube so it cannot slide off, as it sits on the pivot pin and I can use two allen bolts as if loading a tube into the projector normally.

I also drilled and tapped two more holes for two long allen bolts to tilt the plate forward for leveling at the screen.

All wiring reaches okay except the fourteen pin neckboard umbilical; I made a longer one about twenty inches.

I just select COLOR, 2 to operate the loose tube as if it were the green tube installed. There is usually no need to operate any of the installed tubes, the tube under test would not converge anyway due to the odd angle.

Since the green VIM video feed is hotter than red or blue, I keep contrast under 30 unless evaluating stig or flare.

My test machine is a 9500 Ultra but an 8500 would work just as well.

Don't test tubes without one!

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

I do what Tse did, and on his testbed machine he only runs a single tube. The multi-pin connectors on the unused circuits are jumpered, pins 7 to 11, which makes the CLM happy and it thinks that three tubes are connected.

I got some very handy ribbon cable extenders that allow me to lay the FGM and HDM boards flat on the chassis, (with a layer of insulation under them) which makes magnetics adjustments a breeze.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Hey

Try this: put an old type neckboard on blue. Measure the blue G2 on the neckboard at the tip of R76. If it is way low, take the neckboard off of the tube pins and measure again, let us know what you find. Maybe the tube is loading down the G2.

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

Interestingly, VDC makes a little adapter circuit card, part number 65494-01 that connects pins 2 and 6 together. It's attached to the tube UNDER the tube base. It allows any attached tube to be able to use either 2 or 6 for the G2 connection.

Quite a handy little board, actually. I'd install them on every tube just for courtesy's sake.

So there's no problem with connecting 2 and 6 together, apparently. Otherwise, why would this little jumper board exist?

I am thinking more and more than this blue tube has an internal short. I'm going to yank it out tonight, put in a tested blue
assembly in its place, and by doing so, pretty much prove it. Then I'll tear down the assembly and look for any visible issues with the electron gun assembly, not that I can do much about a defective tube other than recycle it.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Hey

Some neckboards take Pin 6 to ground by 330K resistor, that's why it matters.

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

Ah. That'd be LUGs that need that resistor, right?

I want to be sure because it would be silly to not get the best out of these tubes by failing to add a certain resistor or something.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

No

No no no. LUGs take G2 in on Pin 6. 330K to ground on Pin 6 is standard for LCP09s. 330K to ground on the G2 feed takes 500 volts down to 80 volts, and may kill the picture. I'll shut up now.

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

Thanks. I'm a little bit confused on all the subtle differences between how the neck cards should differ between LUGs and LCPs.

In part, because the LCPs in my own machine take G2 on pin 6. (They were made to AmPro specs and were pulled from one of the last 4600s ever made, actually it was auctioned off still on the assembly floor.)

It'd be just a little bit easier if there weren't so many "special cases" regarding tube pinouts and spec changes.

mp20748 · Posted: Tue Apr 26, 2016 11:11 am Post subject:

I had a dream last night that CJ had finally swapped that neck board with one that matches the Other two, but then I woke up this morning. Well, there's always tomorrow.

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

Actually I forgot to mention that. The FIRST thing I did was remove the hot running neck card and swap in a regular 50-2038 series card. Nearly lost fingerprints to that hot card in the process! I'd be surprised if it wasn't damaged.

Putting a "regular" neck card on it did nothing to alter the symptoms. So I must conclude that the tube itself has an internal short. That LC assembly is coming out some time today to be swapped with a spare. Maybe I'll see something interesting in the neck when i take the magnetics off it.

The VDC made neck card found on the blue tube is the "compatible" 03-270340 card that VDC's documentation says can be mixed and matched with the 50-2038/2039 series. NOT the "incompatible" 81771 series cards which have to be used only with other 81771 cards.

I am VERY clear on these mix and match rules. And even then, I would rather not mix and match even a 0340 with a 2038/2039 card if I have 2038/2039 cards available. And I DO have those cards available.

So that line of inquiry can be dropped now, OK? I've taken crap for it from at least two people who haven't even been in this topic yet and in every case, I already knew the neck card swap rules and haven't violated them.

I don't particularly care for being blamed for a mistake that I didn't make.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4379 Location: Phoenix

Hey

If you swap in another Ampro-spec'd tube, you may have the same problem with G2 loaded down.

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

Different machines, no related problems. I have LCPs in my own personal machine but they're AmPro spec tubes with G2 on pin 6. That machine is not at issue and has been running trouble free for the last ten years.

I have no other LCPs with G2 on pin 6. But I don't yet know what's hiding under those tube covers.

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

Tube tested in another chassis with a verified good neck card, tube is fine.

Turns out that apparently my test neck card chose that particular moment to die. It WAS good. Now it's not.

barclay66 · Posted: Wed Apr 27, 2016 7:24 am Post subject:

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

I said they're LCPs. I didn't specify the ENTIRE model number. Yes, they are P19LCP07s.

barclay66 · Posted: Wed Apr 27, 2016 12:30 pm Post subject:

OK. It's just because when people here write about LCPs, they normally refer to the P19LCP09 as it is the typical tube to be found in a 9'' Marquee (except for those late models using LUGs)...