Hawes Electronic Television Archive by James T. Hawes, AA9DT

How We Built Lucitron® Panels

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About Bob Mitchell

Photo: In Lucitron's turbo pump room

(A) Bob Mitchell & Mike DeJule with a Lucitron 34B panel (about 1986).

This page is a memoir about Lucitron, a small R&D company in Northbrook, IL. Lucitron pioneered flat-panel television in the 1970s and 1980s. Panel engineer Bob Mitchell and I contribute our memories about the company and the panel-design process.

Bob built display tubes for Mike Dejule to evaluate. (DeJule was the engineer who usually designed the panels. He was also a Lucitron vice-president.) Along with his management responsibilities, Bob personally built all the panels. That task included these steps...

  • Depositing phosphor
  • Etching glass
  • Building cathodes
  • Degreasing
  • Fritting,
  • Assembling, etc.

Bob begins our story with an examination of panel assembly at our Northbrook facility. (I'll join in with a few thoughts later on.)

Joe Singer's Cane-Pulling Method


Joe Singer produced our glass cane. (Or maybe he even invented the process.) Glass cane began with a two-inch glass cube. Bill Irvin (one of our star machinists) would mill a groove in each side of a two-inch-square glass cube. The result of the machining was sort of an I-shaped block. I remember Joe's cane-pulling method, too. Joe would put the block in a special oven. This oven mounted to a tripod-like support. The “tripod” raised the oven off the floor.

Joe heated the glass block until it melted. In the bottom of the oven was a tiny hole. Gravity would draw the melted glass out the hole in the oven. The result was our glass cane, with a groove down each side. The final width of each cane was only about four tenths of an inch. Joe would cut the melted glass to the three-foot lengths that we needed. How amazing that each glass cane was a perfect size every time!

On track. Remember the grooves that machinist Bill Irvin milled in the glass block? Our nichrome flat leads (electrodes) would slide into those grooves in the glass cane: Just like a train on a track (most of the time).

Photo: Vertical milling machine

(B) Bill's vertical milling machine looked something like this one, except it was green. (Stock photo)

Line drawing: Glass cube and glass cane

(C) Bill milled two grooves in a glass cube. Joe heated and stretched the cube into a long glass cane.

Joe Singer's Glass Cane Operation

Photo: Glass cane honeycomb

(D) Joe Singer's cane honeycomb

We sprayed the cane with frit. (Frit is more or less like “glass solder.”) Then, we laid the cane out in a jig, horizontal and vertically. I (Bob) would fire the cane.

Waffle. What came out of the oven looked like a waffle. This was the point when we'd slide the electrodes into the cane channels. At times, this operation was a headache. If a spot of frit was in a channel, the electrode wouldn't slide through.

Jam. If we couldn't clear the jam, we had to start over. To make things worse, we'd have another channel right below with the same issues.

After we completed these tasks, four rows of electrode holes had to line up.

Line drawing: Lucitron electrode (E) Section of electrode or “lead” (not to scale). Lucitron technicians slid such metal electrodes into slots in the glass cane. (4.)

IBM Trek

Photo Composition: Van on the way to IBM HQ, NY

(F) Cary Stone and Bob drove a van to IBM headquarters. (Collage, using stock photos)

First sale. We sold our first flat-panel display to IBM. Before our model 34B, we had a different panel. The earlier panel was small. It measured roughly eight by 10 inches. Cary Stone and I delivered it personally to IBM. There, we set it up and demonstrated it. IBM purchased this panel for testing. But I don't think IBM ever bought the 34B.

The panel that we delivered had 90-horizontal by 120-vertical lines. The (photo-etched) leads came complete with each panel.

Insulators & Leads

Photo: Insulators

(G) Insulators from Bob's collection

Insulators. We made our insulators out of ceramics with the same expansion coefficient as the glass. I would spray the insulators with frit on both sides. Then, I'd lay on leads and fire the whole piece as a sandwich. In its time, the insulator for the 90-by-120 panel was a breakthrough of sorts. This ceramic insulator was the largest that we could then produce.

Leads. We produced leads for the 34B panel the same way. But we had to cut the leads to shorter lengths. Then we'd slide them into the channels in the cane. (The insulators were 60 thousandths of an inch wide, and 20 thousandths thick. How surprising that I still have a set of them!)

Smaller panels


JAMES. I have a question about the smaller Lucitron tube that you and Cary Stone took to IBM in New York State. Was this the same type as Al Hollander tried to market to Ball and Mead?

Photo: Big and small dogs together

(H) Symbolic picture: The big dog stands for our 34B panel. The little dog stands for our earlier, 90 x 120 panel. Both had a distinguished pedigree! (Stock photo)

BOB. I don't think so. The goal was to make large, flat panel tubes. The tube that we sold to IBM was proof of principle. I don't remember going back to that size, even for color.

JAMES. Al Hollander would stop into our electronics workshop to chat. He told me and Val Chishevsky that Mead might market a mobile display. Al had pitched our large 34B panel, but Mead had wanted something smaller, for car or truck use. I imagined something that might fit in a glove-box space, maybe two units wide by one high. Al didn't tell us the details. Unfortunately, Al never closed the deal.

BOB. We did make some small tubes for tests. The one-to-two-inch tubes that we built for experiments were quick. A lot of times, we just epoxied them together. Nothing like trying to frit something together and have it break, or move out of alignment!

Gaps Between Columns on the Panel

Photo: Bob views his own image on 34B panel

(I) Gaps between picture columns

JAMES. Did you have a plan to eliminate the gaps between picture columns? These gaps are visible in the panel photos.

BOB. Those vertical lines are a piece of cane fritted to the faceplate. The cane was there to make a solid connection between the front and back plate. Our goal for this connection was to prevent implosion.

In the 90-by-120 panel: I believe that I spray-fritted the ceramic plate to the faceplate. Then I settled phosphor through the holes.

Transadmittance Bridge


JAMES. In the lab, Schmitt and his assistant tested water samples for transadmittance. They probably also performed other tasks, but I'm not familiar with those. (How did you use the water in making the tubes? Was it a lubricant during machining?)

Photo: Transadmittance bridge (wheatstone 
      bridge with JFET amplifier)

(J) The transmittance bridge that I engineered wasn't as posh as the pictured item. Mine had a one-JFET amplifier. The output device was an LED, instead of the meter in the photo. The JFET operated off a 9-volt battery. (Stock photo)

Bridge. I only know about the water test because I repaired the lab's transadmittance bridge. Our lab used this bridge to test the admittance of water samples.

Inside the bridge were two obsolete vacuum tubes. The bridge amplifier might have been a 37 triode. The output display was (I think) a 6E5 magic eye. If either one had failed, I'd have had to seek a replacement at an antique technology dealer.

Resistor. Fortunately, the problem was just a resistor that had decreased in value. A decrease in a resistor is so rare that I saved the part! (Usually with age, carbon resistors increase in value. Maybe this part was a metal film type. The package was unusual.) Nobody else in the shop could fix tube technology. So I was the elected serviceman, despite my imperfect repair skills.

Solid state. I also designed a solid-state version of the bridge circuit for Schmitty. Margaret Hultquist built the circuit for me. In my circuit, a 2N3819 JFET stood in for the 37 triode. A red LED stood in for the 6E5 tube. There was a bridge balance potentiometer, just as in the tube circuit. I don't recall the values of my bridge resistors. Maybe I copied them from the tube circuit. A nine-volt battery powered my model.

As far as I know, Schmitty never used my bridge. I understand. I had no way of calibrating it. I did test my bridge, and found that it could read a 100M resistor. (I couldn't find such a resistor in our stock, so I built it from 10M resistors.) That would translate to 1 µS transadmittance reading (I think). The resistor represented the real part of transadmittance, which is technically “transconductance.”

Water for the Color Tubes

Art: Lunchroom food, tough to swallow

(K) Lunchroom: Off limits for eating! (Stock photo)

BOB. Nobody ate in our lunchroom. I used the lunchroom to deposit my phosphor on the front screen glass. I used deionized water which was delivered in a tank. Or maybe the unit took tap water and removed the minerals. If you got the chemicals in that room in your food, they'd kill you!

BOB. I'm pretty sure that Schmitt and his assistant were working on color TV. For a color tube, we needed to deposit each color individually. We had to mask off the parts that we didn't want to coat. If I remember: Each red, green, or blue strip was 60 thousandths of inch wide. We deposited each strip between the canes we'd fritted on the faceplate.

Hot Spot in the Panel


JAMES. These were handmade panels. I know that sometimes, an imperfection would creep into a tube...

Photo: Panel with hot spot

(L) Panel with hot spot (middle)

BOB. Yes. Remember, we didn't build these panels in a clean room. Despite our best efforts, sometimes contaminants snuck into a tube. The result of contaminants is a hot spot. The high voltage takes the path of least resistance and starts an arc. If you look closely, you can see how the hot spot starts at the arc and spreads outward.

I'd spend hours in a dark test room, looking for hot spots. I'd start low with the high voltage, and slowly increase it over time. When a hot spot started, I'd lower the HV. Then I'd leave the HV there for an hour. After that hour, I'd increase the HV again, to see if the spot would reactivate. If the spot was bad enough, I'd pump out the panel again. Then I'd leave the panel there for a few hours under vacuum. Next, I'd refill the panel with Argon.

Bob Says Good-Bye to the Panel

Photo: Good-bye to the panel

(M) Bob: “Good-bye” to the panel

JAMES. A wistful moment (April 28, 2023): Farewell to a scrap of yesterday. This may be the last Lucitron 34B Flatscreen panel on Earth. It's the same type panel that Lucitron shipped to the U.S. Navy, back in 1986 or so. In the photo (Left), Bob hands over the Lucitron panel to folks who will (gently) drive it to Hilliard, OH. There, the panel will go on display at Steve McVoy's famous Early Television Foundation Museum.

BOB. They just took the flat panel. Thanks, Steve McVoy, for saving a piece of television history.

Lucitron: Pioneering Flat-Panel Displays

Lucitron's skunkworks: Our video panels were high tech. Yet baked into each panel were both advanced engineering, and educated guesswork.

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1. Bob Mitchell, e-mail message to editor, November 28, 2020.
▶Re: Bob summarizes his Lucitron experience & responsibilities..

2. Bob Mitchell, e-mail message to editor, May 25, 2022; Bob Mitchell, e-mail message to editor, November 28, 2020.
▶Re: Description of Joe Singer's cane-pulling unit (glass cane).

3. Bob Mitchell, e-mail message to editor, June 3, 2022.
▶Re: Joe Singer's Glass Cane Operation.

4. Bob Mitchell, e-mail message to editor, August 27, 2022.
▶Re: Electrode (lead) details, including: • Pilot hole for pulling lead with pick. • Taper at each end of electrode. • Round hole shape.

5. Bob Mitchell, e-mail message to editor, June 1, 2022; Bob Mitchell, e-mail message to editor, November 28, 2020.
▶Re: IBM Trek, from Illinois to New York State. Cary Stone & Bob Mitchell drove to IBM headquarters in New York to demonstrate one of our early flat-panel displays.

6. Bob Mitchell, e-mail message to editor, June 1, 2022.
▶Re: Insulators & Leads.

7. Bob Mitchell, e-mail message to editor, June 19, 2022.
▶Re: Smaller Panels. Al Hollander's discussion of possible smaller panel, with our prospect Mead Products LLC. Nothing came of discussion.

8. Bob Mitchell, e-mail message to editor, June 3, 2022.
▶Re: Gaps between columns on panel.

9. Bob Mitchell, e-mail message from editor, June 19, 2022.
▶Re: Transadmittance Bridge (My email, plus memories that I've added since email).

10. Bob Mitchell, e-mail message to editor, June 19, 2022.
▶Re: Deionized water for deposition of color phosphors.

11. Bob Mitchell, e-mail message to editor, June 21, 2022.
▶Re: Hot spots on the panel. How Bob analyzed & serviced them.

12. Bob Mitchell, e-mail message to editor, April 28, 2023.
▶Re: Bob says good-bye to the panel. Helps to load it into van for ride to Early Television Foundation Museum.



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• Photos A, D, E, G, I, & L, copyright © 2022 by Bob Mitchell. All rights reserved. • Photo M, copyright © 2023 by Bob Mitchell. All rights reserved.
• Line art C, E, copyright © 2022 by James T. Hawes. All rights reserved. • Text, copyright © 2022 by Bob Mitchell & James T. Hawes. All rights reserved. (Story editing & photo retouching by James T. Hawes.)
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