29 May
2001
29 May
'01
1:48 a.m.
On Fri, 25 May 2001 19:12:36 +0100 (BST) Tony Duell
<ard(a)p850ug1.demon.co.uk> wrote:
[Williams tube memory]
That's how I understand it, yes.
The memory was also the only output device in the
"Baby",
since the CRTs had normal phosphor coating and the bits
glowed. Programs would halt, and the results would be read
from the CRT face.
Are you sure? I thought there was a metal electrode over the front of the
CRT, and the signal picked up from that was fed back to refresh the
charge image on the CRT face (yes, this is a simplification). So if you moved the electrode to see the screen,
you'd lose the memory
contents.
Absolutely. There's a photo of a dual Williams tube module
in one of the books, hinged open in just this way.
I can well believe having a second CRT coupled up,
which had the same
deflection signals, and in which the beam intensity was controlled by the
amplified singal from the pickup electrode. That would display the memory
contents as an array of dots.
I think that must be how it worked. However, I've never
seen this clearly and completely explained! There's a CRT
lying in one of the racks in the middle of the photos of
the "Baby", above the input switch bank. The actual store
is in another rack, though.
And VCR97s [1] were not exactly uncommon,
adding a second one would not have been a problem
It would have been quite easy to wire up, yes.
[1] Valve Cathode Ray 97 IIRC. A very common radar CRT
from WW2. Common
enough that _I_ have one in the junk box.
Since you have one, could you tell me if it's
electrostatically deflected? I presume it is, making it
resemble an oscilloscope tube more than, say, a TV picture
tube?
--
John Honniball
Email: John.Honniball(a)uwe.ac.uk
University of the West of England