vac tube clock rates / was Re: neon glow lamps (was TTLhomebrew CPUs) in HP counters

dwight elvey dkelvey at
Sun Jul 15 01:06:16 CDT 2007

>From: "Chuck Guzis" <cclist at>

>On 14 Jul 2007 at 14:35, William Donzelli wrote:
> > Without going to the old industry rags (I am not home now anyway), I
> > would bet that the upper limit on computer tube operation is due to
> > the interelectrode capacitance and spacing issues (the actual distance
> > between the cathode and plate - it become criticals when you see that
> > the electron transit speed is actually not that fast). I would also
> > bet that the speed could have been increased if the tubes shrank -
> > using subminis instead of minis. Speed would probably go up, but cost
> > would also skyrocket.I doubt any commercial maker would have wanted to
> > pay that price.
>When I used to shopping on Chicago's Michigan Avenue "Surplus Row", I
>used to see lots (boxes and boxes) of PCBs with submini wire-lead
>dual triodes on them (usually about 6 per card).  I bought them and
>used the tubes for HF operation (very handy in a cascode
>configuration) and lots cheaper than Nuvistors.  Since most of these
>stores dealt in defense surplus, I suspect these were part of some
>military computer as most of the boards were wired as flip-flops.
These might have been use for encryption. They used a lot of
LFSRs in these. That would be mostly flops and little else.

Need a brain boost? Recharge with a stimulating game. Play now!

More information about the cctalk mailing list