CurtPalme.com Home Theater Forum

[cmjohnson]

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Simple enough question: Does anyone here have the Panasonic datasheets for any of the various Panasonic/MEC/Matsushita type tubes that are found in most of our projectors?

In particular I'm looking for the P19LUG data but I'll take what I can get. P19LCP, P16LNN, P16LNQ, 180DMB, whatever.

Reason: I want to find out how the added G3 grid on a P19LUG actually works and how to use it to get best sharpness out of the tube. And along the way, find out how the drive circuits for the other parts of the electron gun assembly affect the qualities of the image as well.

[barclay66]

Hi,

I only have some excerpts from a datasheet. The whole document should have 27 pages.
Some portions have been posted by member Ile. So maybe he has the full document...

Regards,
barclay66

[gjaky]

That grid is usualy referenced as "KH" grid, but historically H means heater K means cathode, so for me this could indicate that this a an added grid between Cathode and Heater. Furthermore the datasheet indicates interelectrode capacitances of 2.7pF and 5.9pF, when this KH grid is exploited. On the other hand CRT amplifier design notes usualy claim a typical CRT capacitance is around 10pF (and I myself measured the same thing on regular CRT projection tubes). So I believe that this KH grid is only lowers interelectrode capacitance mainly between cathode and heater, which aims better bandwidth as CRT amplifier bandwidth is limited by load capacitance on the first hand. On the LUG the spot size migh be better than LCP but I don't think that is a result of the KH grid.

[cmjohnson]

The LUG electron gun assembly does have a smaller aperture. This is what enables the smaller spot size.

The third grid, which reduces interelectrode capacitance, increases the available beam modulation bandwidth capacity, thus enabling higher resolution.

On a CRT resolution is related to spot size in a functionally equivalent manner to pixel size vs. panel resolution on a fixed pixel display system.

If the interelectrode capacitance were down in the femtofarad range (below picofarads by an order of magnitude) then you could have enormous available modulation bandwidth but if the beam spot size isn't reduced accordingly, you're not going to realize that resolution improvement on the CRT face no matter what you do.

I'm trying to gain a greater understanding of how to control all the elements of the electron gun and the theory behind it as well. The idea is to understand how a neck card can be optimized to drive the electron gun elements at their peak possible performance level.

A lot of people never give the electron gun a second thought. They don't even realize that there are elements in them that will gain a high voltage potential on them simply by being in the path of the electron beam. And that charge has to be controlled and bled off, but HOW you bleed it off has an effect. Bleed it with a large resistor to ground and the element operates at a higher voltage, bleed it to ground with a very low resistor value and you may end up shutting down the picture and maybe even damaging the tube.

There are elements in the electron gun structure that don't even HAVE a connection pin to the outside world. They charge up to a
certain voltage during operation by picking up stray electrons and inducted charges, but they have no outside connections. Despite this they're important.

[gjaky]

Then the question arises, doesn't Clinton / Lexel / Thomas had datasheets on these tubes, since they all manufactured them...

[cmjohnson]

Clinton is gone, no longer doing anything at all. It was a VDC subsidiary. I have some Clinton LUGs.
Lexel is also a VDC subsidiary, still (last I checked) active and able to make tubes. I have some Lexel LUGs.
Thomas is "different". They make EQUIVALENT tubes. Functionally the same, not necessarily the same in the details.
They're still around. I have ONE of their tubes, a green LUG equivalent, and it works but it's rather dim. Toob bad, it's otherwise perfect. Which makes sense. If it was dim from the moment it was made, why would you use it?

I can use that one for testing purposes. Well, I have a LOT of tubes I can use for testing! More than I'll ever need.

I'm fairly sure that VDC controls document release by their subsidiaries. So asking VDC is most likely to yield results,
but I've asked in the past and gotten nowhere.

Mikado is the only independent maker of Panasonic spec tubes these days. And my request for this data was politely refused.
I guess I should have sent them a golf hat or something.

I'll ask VDC AGAIN. At this point they're only doing repair support on CRT projectors so the tube specs are not of any additional interest to them.

[gjaky]

Then I'd ask Scott if he ever saw a full datasheet on LUG or else, because if he did not see any , then most likely VDC doesn't even have one...

[cmjohnson]

Considering that Panasonic transferred the entire data package for the relevant tubes to VDC so that VDC and its subsidiaries could make license built tubes to those specs, and Panasonic fully supported the transition including proving equipment and training for tube production, I think it is highly likely that SOMEONE at VDC or a subsidiary has seen that document. And may still have a copy of it.

[bklyn1]

Im pretty familiar with these types if you have any questions. I know this is a year old reply. Im a CRT engineer and may be able to help. By the way, the KH grid is a capacitance matching grid. It actually surrounds the cathode shank. Its on the LUG, not the LCP and I havent seen a notable difference in its use regarding resolution.

[cmjohnson]

Let me guess, Thomas Electronics? I know of no other CRT manufacturer in New York.

I did end up with the Mikado data sheets for both the LUG and LCP.