Post by Ferg
No. It is the normal behaviour on the 1520. I have seen this on others,
and back in the '80s when mine was new, it did that then too.
It's getting itself oriented during its power-up initialization. First it
drives the "head" to the left stop. It doesn't have a switch or other
sensor for this, so it simply does enough motor-steps to place it there,
even if it had been at the full-right position at power-on. If it *wasn't*
full-right to start with, then it hits the left stop and "grinds" its way
through the full number of steps -- kind of like a 1541 head-bump.
After this, it orients the rotating four-color pen turret to the "black"
position. It does have a sensor for this: there's a little bar magnet set
into the side of the turret which activates a magnetic reed switch on the
carriage's frame. You can hear this second stage, too -- a
"ticka-ticka-ticka, ticka-ticka-ticka" as it steps the turret around.
Finally it draws the four-color squares to get the pens started, feeds to a
new line, then comes to rest.
You can avoid the nasty grinding by pressing the pen-change button and
letting it ride over to the full-right position before turning it off (you
ought to anyway, so you can take the pens out and cap them -- they use
liquid ink and will dry up if you leave them in the plotter).