14 Sep
2012
14 Sep
'12
12:17 p.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.
You will find you need quite a low voltaeg to get the pins to extend.
Typoca;;y these ehads are runm from 24V or 36V supply rails i nthe
printer, but a 5V bench supply will normally operate them,. The actch is,
of course, the operate a lot more slowly (due to the inductace of the
coils) on the lower votlage. That's why the higher voltage is sued in
operation.
YEs, they will over heat if left on too long. But you can certainly test
a head in this way, and clean the exposed part of the pin without
damaging it.,
Of coruse you are not going to leave the head unattended when doign
this. You are likely to be hand-holding the head. You will notice if
it's getting hot.
Incidentally, if you ever have to reasseble the X-axis drive suystme of
the HP7245 printer/plotter, it helps to be able to lock the drive pulley
whenyou are widning the drive cabel round it. I have found that
energising one winding of the drive stepper motor (again, only 5 or 6
volts) will do this, and the motor doesn't get hot in the time it takes
ot put the thing together.
-tony