29 Aug
2008
29 Aug
'08
noon
Paul Koning wrote:
I found some work on the net (and did some of my own
based on that) on
Spice models for vacuum tubes. It's not a standard offering in Spice
packages but it's easy enough to define a model, and given a data
sheet with characteristics curves you can quickly match the model to
the data sheet.
(The circuit I'm modeling is being very uncooperative, but as far as I
can tell the tube models are not at fault in this.)
Spice might be a handy way to verify an existing schematic and to
discover how to tweak it for another tube and/or another plate
voltage.
DI Gerhard Kreuzer wrote:
to make use of my spice tool set was indeed the
first idea, but I
dont have enough time yet so I didnt answer.
Its no problem, there are still models for tubes available and its
not to hard to make new models for the originally used tubes.
...
Sorry, that I am short?with time, but I am very interested on this
project and as I can spare some hours, i will join, if possible.
It could be interesting if someone made up
a SPICE model of the ASM to check some resistor values. I have no experience
using SPICE and am not acquainted with how flexible it is, but it would then be
interesting to exercise the model to find out how reliable the design would be,
that is, what degree of resistance and tube variation is tolerable.
I have the set of resistor values from the appendix of "The First Electronic
Computer", as well as a set of values from my own attempt at calculating them.
Either or both might provide a starting point for input to the model.
...sheesh, I just went looking for those values, found them .. but I also found
a spreadsheet model of the entire ASM that I forgot I had created. I
measured the characteristics of an actual 6C8 in a simple circuit and used the
resultant values in a lookup table in the spreadsheet to mimic the transfer
function of the tubes. The model, at least, appears to work, but my R-network voltage
calculations were rather simplified.
I'm sure a SPICE model would be much better, and may show up problems.