6 Jun
2009
6 Jun
'09
10:28 a.m.
However, the paper does not feed correctly. On
inspection, I've already
found that the grease in the little solonoid that lifts the head from the
paper when it advances has turned to something more sticky than honey.
I'm in the process of addressing that.
This is a well-known problem on all sorts of devices. Someitmes the
grease will soften with common solvents (propan-2-ol, etc). There's a
green grease used in some camera lans mounts that goes rock hard with age
and nothing wil shift it short of scraping it out....
I also see that the stepper motor that actually turns
the platen (or equiv
of) is not making a full increment each time. Sometimes it advances but
other times it de-advances. So, something it messed up in the stepper
circuit or the grease in that stepper motor has turned to honey too.
Maybe you've lost the drive to one of hte stepper phases. That can make
them step in thwe wrong direction sometimes.
This is a really cool machine though. I grew up with this thing hooked
to my first computer (an MEK6800D1 eval board) in 1975. I went through
thousands of rolls of thermal paper as I typed in machine code to MIKBUG's
'*' prompt one line at time :-)
There's no microprocessor in the thing-- not even a UART. It's all done
with 7400 TTL and electronically, it's extremely fixable.
The 733 is like that too, although there's probably at least one ROM (the
character generator). From what I rmember there's a cardcage of PCBs
between the 2 tape drives in the ASR add-on (behind the swtich/LED panel
in the middle -- in fact I think that's mounted on the frontmost PCB in
the cage). Anyway, about the most complicated chip on those boards is a
little bipolar RAM. No microprocessor.
It's pretty funny but as soon as I took the lid off the Silent 700,
the smell of that plastic brought back the same impressions of coolness
and excitement I had as a kid.
Everything else is on the back burner now-- gotta get this baby
printing right! :-)
I'm almost convinced to dig mine out and have a go with it... Too many
projects, not enough bench space...
-tony