On Thursday (01/29/2009 at 07:22PM +0000), Tony Duell wrote:
supply problem because as soon as you try to
punch all eight holes with
the front panel test button, the power LED dims and the punch jams,
What type of mechanism does this punch use? In my experience there are 2
basic types :
1) Solenoids to driectly operate the punch pins (that is, the punching
force comes entirely from the solenoid), and a (stepper) motor to move
the tape. For example the Facit 4070
2) A continuously rotating camshaft (normally with a mains-powered
motor). The solenoids operate linkages (or clutches) to operate the punch
pins, the punching force comes form the motor, not the solenoids. Anther
solenoid opeates the tape feed mechanism, again the power comes from the
motor. For example the Teletype BRPE, Tally 420, etc.
Needless to say the solenoids in the second type are much smaller and
take much less current.
This unit, GNT 3601, is type #2 that you describe. The root of the
problem was that the pins were seized in their slide-ways and when the
little solenoids tried to push them, they could not. Only the pin for
punching the feed hole was really movable. I loosened them with some
alchohol, moved them back and forth a lot and then put a tiny amount of
light oil on them. Free as a bird and smooth as can be now.
from lack of umph to complete the mission. It could also be
jamming to start with and that causes the power drop I suppose.
Can you tuen things by hand (power off, of course) and operate the
solenoids by hand to see if the mechanism can be got to work?
External to the punch mechanism, everything seemed OK... but deep
inside these pins were binding and nobody was gonna play that way.
The solenoids are very tiny and completely enclosed inside the punch
mechanism. The only thing external is a pulley around which goes
a round belt over to a DC motor which provides the power. There's a
bigger solenoid as you describe which advances the tape but that too is
totally enclosed within the punch assembly.
Now I'm working on figuring out the serial and parallel interfaces.
The brains are an 8048 microcontroller and then it looks like the serial
interface is handled by a classic old AY-3-1015 UART, which I'm assuming
front-ends the parallel interface. Lots more discovery there...
I obtained a manual for a GNT 4604 unit (thanks Bob!) and we'll see if
any of the signals line up with that.