14 Sep
2012
14 Sep
'12
12:22 a.m.
Not a bad way to test but do remember that the head solenoids were designed
for pulse operation so do not power more one at a time and don't leave the
power on for too long.
Regards
?
Rod Smallwood
?
?
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Tony Duell
Sent: 13 September 2012 19:24
To: cctalk at classiccmp.org
Subject: Re: Selenar Graphics II (Was: DECWriter II LA36 being given away)
Quite so ..
Although I did not say do not take it apart I quite agree.
Heads would always be replaced never repaired.
Howe3ver, people here often do repairs that no field servoid would
contemplate.A motor would not be reound in the field, but I've
done it several times (in an LA36, an HP9125 plotter, etc, etc, etc).
Simialry, many of us (OK, me at least) do component-level repair on
machines that were nromalyl field-repaired by board-swapping.
Hence my warning. These dot matrix printheads are not at all easy to
reassembel without a new set of p[rinmt wires. I would avoid taking them
apart!
I do remember a field service engineer gently moving
the print wires with
a
pair of needle nosed pliers where they were visible
underneath. I was
surprised how far they stuck out in front of the final guide.
A gopd adjustable bench supply ('good' meaning to goes down to 0V, which
a lot of modern ones don't) is useful here. Connect it between common and
one of the print solenoid wires (with the head unplugged from the driver
board, of course) and slowly turn up the volts. The pin will come
forwards, it foesn't take much votlage to do it either. The tpyically
stick out 2 or 3 mm when fully driven.
-tony