CurtPalme.com Home Theater Forum

[Chad B]

I'm doing a first time setup and calibration of a 9500LC, and am having problems with the green tube (a brand new LUG).
Problems:

1. Green tube blooms and gradually loses focus above contrast setting of 25. By 45, it's looking fuzzy. By 65, it's very poor, and by 75 it starts to bloom severely. Image is way too dim at 25.
2. Green drive has little to no visible effect. When adjusting 6500 col temp preset, the green G2 works, but the green drive does not. R and B drives work properly.
3. Stigmatism is adjusted and in good shape; defocused green dots are round with no flare.
4. Green focus has to be near 0. Anything above 5 or 6 starts to look fuzzy. R and B focus are OK around midpoint, which is 50.

My customer and I would greatly appreciate any help. Thanks!

[CZ Eddie]

I would suspect a cable not being connected where it's supposed to be.
Verify cable connections on all modules first (VIM, HDM, Focus). If it looks good, then reseat the connections.

If still having problems, then try swapping all the red cables over to the green and vice versa.
This way, your internal menu should come up on the red tube.
Then try comparing the difference in behavior between red & green.

[cmjohnson]

I'd suspect a bad neck card. I would exchange the green and red neck cards...or green and blue. If the problem follows the card, it's the card.


The symptom is similar to a low anode voltage condition. You could have a bad anode lead or it's not making good contact. But this is not to be messed with if you're unsure of how to discharge and bleed off the anode potential before messing with it.

To test this, I'd swap anode leads between green and any other CRT, at the splitter block.


CJ

[Curt Palme]

Guys, the set came from me, and has one of Terry's greens in it.

I did observe the focus to be best at about 3-4. I know that's low, but tried 2 focus yokes and two HVPS, and that's where it remained. Tube is razor sharp, or should I say..was.. (ran it for 24 hours or so before shipping it out) until the contrast hits about 65, at which point it would defocus. Every new LUG I've had here does that, and I've discussed it here before, and others agree, above a typical contrast range, LUG tubes do defocus.

Absolutely the green drive worked here, I preset the G2s and drives before I send them out, and I would have caught that.

I also agree that there could be a bad CRT socket and MAYBE something happened to the HV splitter in transit. I'll shoot the customer an email to try swapping HV leads out of the splitter. I'll have to send a modded CRT socket down, as the other tubes are LJE tubes.

[Curt Palme]

Guys, the set came from me, and has one of Terry's greens in it.

I did observe the focus to be best at about 3-4. I know that's low, but tried 2 focus yokes and two HVPS, and that's where it remained. Tube is razor sharp, or should I say..was.. (ran it for 24 hours or so before shipping it out) until the contrast hits about 65, at which point it would defocus. Every new LUG I've had here does that, and I've discussed it here before, and others agree, above a typical contrast range, LUG tubes do defocus.

Absolutely the green drive worked here, I preset the G2s and drives before I send them out, and I would have caught that.

I also agree that there could be a bad CRT socket and MAYBE something happened to the HV splitter in transit. I'll shoot the customer an email to try swapping HV leads out of the splitter. I'll have to send a modded CRT socket down, as the other tubes are LJE tubes.

[tse]

The green drive is limited to a very small adjustment range by the firmware. It is only a couple of percent from min to max. Just set it to 92% and use the red and blue drive for the white balance. Adjust the static focus (center area) with contrast at 50% and input video at 0.7vpp (100% white). The tube should focus good there.

Scott

[cmjohnson]

Isn't there technically supposed to be a modification that should be performed above and beyond moving the bias lead to the appropriate pin (usually pin 6) when using LUG tubes?

If so, would it have any effect on the problem described?


CJ

[draganm]

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[cmjohnson]

I'm not "implying" anything. Just asking a straight question. The LUG tube is a slightly different animal than the LCP and apparently it gives different results, particularly when mixed into a PJ with LCPs.


But as for the focus range, Tse can answer this question which I'm about to ask:

Does the LUG tube require a different static magnetic field strength for optimal focus, as compared to an LCP?

Marquee yokes can be expected to be calibrated to the static magnetic field strength which is optimal for the LCP tubes (9") or
180DMB tubes (8") and I think that's the same value in either case, 294 Gauss, but as the LUG is a slightly different tube,
it may require a different magnetic calibration value. Scott, is this the case? Do you have a different magnetic calibration value
for the LUG tubes?

If the magnetic field strength of the focus coil is ideal, then when the coil is correctly placed and disconnected from the focus drive
board, then central focus will be very sharp. There are two focus coils in the assembly, a static coil and a dynamic coil. The static
coil is driven to modify the overall magnetic field strength to compensate for slight differences in tubes and in the basic magnetic
strength of the permanent magnets in the assembly. It can add a little field strength, or cancel out a litttle bit. It's driven by a DC
voltage, if I remember correctly. Tse will correct me if I'm wrong about that.

The other focus coil is the dynamic coil. Its field strength is very rapidly adjusted as the electron beam flies across the CRT face,
making small corrections to keep that flying beam in optimal focus at all times It has to make up to three adjustments to the field
strength every single time the electron beam draws a single scan line.


Your LUG tube seems to need a focus yoke that is calibrated to a different value than the regular LCP, OR you have a yoke that is
way off on its magnetic strength. This does happen. If yokes get taken off and just tossed in a box with each other, they can and
will slightly demagnetize each other, especially if there is no keeper ring inserted in the gap. (The keeper ring is a steel tube about the
diameter of the CRT neck and about an inch and a half long. When inserted, it helps to maintain the magnetic field strength of the
permanent magnets in the focus yoke assembly.)


Check this: How is your central focus with the focus yoke totally disconnected from the focus board? (Disconnect the astig cable, too.)

Now reconnect it, find the best static focus value, and try to adjust zone focus. How well does zone focus work?


CJ

[Nashou66]

Has anyone thought of swapping focus coil connections.I didn't read the whole thread, it could be a bad mosfet on the green channel. It sounds like an issue i had after i shorted a channel probing around with a scope.

Swap the red focus connector tot he Green and use the red focus in the service menu to adjust.

Athanasios

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[Nashou66]

I'm wondering if the tube guns maybe got some crud on them in transport. It might cause some voltage irregularities . a few light taps on the tube neck while the PJ is running might solve this issue.

Athanasios

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[Curt Palme]

[Curt Palme]

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[Nashou66]

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