DEC LA180 printer

Tony Duell ard at p850ug1.demon.co.uk
Tue Feb 5 17:00:43 CST 2008


> I just managed to fix the problem with the init-sequence.
> There was a faulty IC "9601PC" by which the controller senses that the
> servo-motor isn't able to turn (paper jam).

I don't know how similar it is to the LA36, but on the latter printer 
there is no 'home sensor' to dtect when the printhead has got to the left 
side. Instead, at power on, it tuns the motor and bangs the head into the 
left side plate, then detects that the motor has stalled (much as you've 
described), and thne running the mtoor fowardsfro a few pulses. That's 
the home position.

There's a nasty failure mode of this, though. The plastic key in the belt 
sprocket breaks and the sprocket slips on the motor spindle. As a result 
the motor never really stalls, it keeps on turning against a rather heavy 
load. Since hte logic board doesn't detect the stall, the motor keeps 
running, gets very hot, and in the ned the insulation burns off the windings.

This happend to an LA36 at Bristol University when I was there. A friend 
and I spent an afternoon rewinding the motor (a replacement motor was 
excessively overpriced!0. 

-tony



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