William Donzelli <aw288(a)osfn.org> wrote: I imagine you're thinking of Williams Tube memory, which was used on various computers before core memory was available, including the IBM 701 and 702 (their first mass-produced electronic computers for scientific and business applications, respectively). Williams tube memory worked by sensing the potential at the face of the tube, not by sensing the beam current. IBM apparently was never able to make Williams Tube memory work reliably at the density that they originally quoted to customers (1K bits per tube), so they scaled it back to 512 bits per tube with twice as many tubes. When core memory became practical, IBM retrofitted the 701s and 702s they had already sold. Meanwhile, Thomas Watson Jr. heard that the 705 team was planning to use Williams Tube memory instead of core because it was cheaper. He apparently said something about the stupidity of using something that doesn't work instead of something that does on the basis of the economy of the former. The 705 shipped with core memory. :-) As did allmost all IBM computers from then until the introduction of semiconductor main memory on the 360/85 and thin-film memory on the 360/95. Does anyone know how RCA's Selectron memory tube worked? I've seen pictures but no explanation. Memory wasn't the only part of early computers that used special and somewhat bizarre electron tubes. One of the earliest CRT display devices was the Charactron. This worked by defocusing the electron beam, using one set of deflection coils to steer the electrons through a character stencil (like a shadow mask), and a second set of deflection coils to steer the electrons to the desired character location on the screen. If memory serves, this type of display was used on Whirlwind. Presumably it was more economical than using a standard XY oscilliscope with either a hardware vector character generator or software. Eric

The lights ("blinkenlights") on some early machines (and even a few not so early machines) were tiny tubes, as well. A bit more simple than a CRT... William Donzelli aw288(a)osfn.org

No, there really were little great grandsons of the 6E5. To quote from *Tube Lore*: 6977 [AKA DM160]; T1 submin. computer indicator triode, blue green glow, fil. 1.0 V @ 30mA; shows no light at Vg -8, full glow at 0 V (AX, MU, RCA, SY, TS) (8-12-57). T1 is the bulb size (tubular - 1/8 inch diameter). The "AX, ..." business means that known makers were Amperex, Mullard, RCA, Sylvania, and Tung Sol. The advantage to these is that they have very good life expectancy - probably in the 30 plus years range. Like other "eye tubes", the main failure one finds is contamination of the target, causing the brightness to decrease. The Packard Bell 250 uses them. William Donzelli aw288(a)osfn.org

At 07:45 AM 8/15/99 -0000, Eric wrote: It was an electrostatic memory tube with 256 bits as 2 16x8 arrays, one on each side of the cathode. X-Y grid wires could be addressed to form a beam (4 +potential wires, 2 X and 2 Y formed a window/electron lens). Beyond were electrically isolated targets. These, by biases to other electrodes, could be charged to 2 different potentials (170V) by the beam. The targets were shaped like eyelets so at the more negative potential, the read beam would be repelled, and at the positive potential, the beam would pass through to a faraday cage and anode where it was read out. There also was a fluorescent screen, maybe for visual readout or maybe for secondary emission amplification? -Dave ps, Cool idea Allison on a vacuum f. triode flip-flop/ readout.

Hi Allison and all, At 08:18 AM 8/16/99 -0400, you wrote: Fair Radio still has similar size ones on a calculator output board (12 displays, 9 segments+ each), US$3.00. I bought one, and haven't traced the circuit except all the filaments are in series. The "grid" appears to be the normal vacuum fluor. mesh, Some might be able to trace the circuit quickly, since there are duplicate circuits, but I'm not one. It has NEC ic's of the time: uPD10 and uPD16 in metal cans, uPD13 in a 14 pin DIP, and 2 others. Round epoxy transistors are the digit and segment drivers. -Dave