21 Dec
2024
21 Dec
'24
9:19 a.m.
On 12/20/24 21:39, Paul Berger via cctalk wrote:
The chain with box drawing characters mention in the
original post where used to print the ALD. The 1403 had
logic that limited the number of hammers that could fire
at once, there was a test routine that would repeatedly
fire the maximum number of hammers it was called the
"Chain Breaker Routine". The only drum printer I ever saw
operating I think it was a Honeywell printer and the
person demoing it printed out some pictures, the printer
could fire most if not all hammers at once which made
quite a racket.
Paul.
I had a BIG Honeywell drum printer on my S-100 Z80 system.
It was from a system used to print from tapes, offline. It
had some odd characters for making boxes on printed forms.
There were shift registers that controlled the hammer
transistors in pairs. Even column characters on the drum
lined up with the hammers alternately with the odd columns.
The same driver transistor was used for adjacent hammers,
but the hammers were actually fired by big SCRs that
alternately powered two power rails. The SCRs were
commutated by big Germanium transistors. While getting this
beast running, I managed to disconnect an important signal
cable and it caused all hammers to fire every character
time, and the hammers pounded the thin metal shield in front
of them. The noise could probably have been heard a block
away! It also blew out the commutating transistors. I was
able to replace them with some TO-3 transistors out of my
junk box, and it worked fine for the rest of the time I had
it. I did use overprints to create some of the extended
ASCII characters, so my Pascal listings could only be read
by me. Such things as curly braces were overprints of ( and
<, for instance. If you printed a full line of * or _ it
made a loud "bump" noise!
Jon