On Mon, 8 Dec 2008 23:22:17 -0800, DaveC put
finger to keyboard and composed:

This is a partial wiring diagram for an early 80's (West) German guillotine
paper cutter:

http://freefilehosting.net/show/42l0i

The goal of this circuit is to energize an electromagnetic clutch coil (m27)
that takes rotational energy from a flywheel to do a task (bring down the
knife blade). This circuit is currently not working.

This machine has no ICs. There are some monolithic rectifier bridges and
discrete transistors (the common symbol for which I cannot find *one* in the
diagram), and plenty of passives.

The transformer (m) primary center tap is connected to 24vdc. Do I interpret
this correctly that the primary is run by a switched dc voltage? (This on a
machine that runs on 3-phase 245vac.) Why?

Maybe this particular clutch requires a higher frequency than 50Hz or
60Hz ???

I can say from experience that other machines of this same manufacturer use a
voltage derived directly from the 3-phase input to drive the electromagnetic
clutch. Why use a switched voltage, I cannot understand.

Is the triangle within a square symbol some sort of odd representation of a
transistor? And the "arrow thing" that feeds them? Ideas?

I'd say it's probably an NPN transistor (plus associated components
?). I suspect that the rectangular block immediately above the two
chopper transistors (?) is probably an oscillator or multivibrator.

Having said that, I can't follow the current path. It appears to flow
into the transformer's centre tap and then out via either end of the
primary winding. It must then flow through the "transistors" into the
"oscillator" because the side paths are blocked by reverse biased
diodes. But the remaining terminal for the oscillator is also blocked
by diodes ...

It seems to me that your circuit is some kind of hybrid block diagram.

Help!

Thanks,


- Franc Zabkar
--
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