14 Jul
2007
14 Jul
'07
11:47 a.m.
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.
Cheers,
Chuck