24 Jan
2006
24 Jan
'06
12:22 p.m.
Hi there,
I've finally got the ribbons for my LA36, unjammed the pins in the
printhead and it is printing. It's not quite right yet, though...
The printhead often jitters backwards and forwards, sometimes several
inches. When you hit "RETURN" it's obviously lost track of where the
head is, and slams it into the left-hand stop, where it sits obstinately
pressed against the spring.
Cleaning up the photosensor bit on the interrupter wheel seemed to help
a little.
Gordon.
24 Jan
24 Jan
12:39 p.m.
Gordon JC Pearce wrote:
Cleaning up the photosensor bit on the interrupter wheel seemed to
help a little.
how freely does the mechanism move on the carriage? sometimes this causes
jitter, though not at rest.
look at the power to the control circuit and the drivers to the servo
motor and
make sure it's not about to blow, and maybe has high ripple on it if the
jitter
is happening at rest.
jim
12:56 p.m.
New subject: Jittery LA36 updated
jim stephens wrote:
how freely does the mechanism move on the carriage?
sometimes this causes
jitter, though not at rest.
Freely enough, with the power off obviously. There is a little
resistance as the ribbon feeds, but not much.
look at the power to the control circuit and the
drivers to the servo
motor and
make sure it's not about to blow, and maybe has high ripple on it if the
jitter
is happening at rest.
It does happen occasionally. I haven't scoped the PSU rails yet but on
the odd occasion that it does jitter at rest, it doesn't sound ripply.
What I have found is that it seems to do it when the opto-interruptor is
at certain positions. Sometimes it will print 1/4 of a line, skip a
1/4, print another 1/4 and skip the rest.
I took the opto sensor assembly off and blew it out with an air duster.
This didn't help.
Gordon.
2:21 p.m.
Hi there,
I've finally got the ribbons for my LA36, unjammed the pins in the
printhead and it is printing. It's not quite right yet, though...
The printhead often jitters backwards and forwards, sometimes several
inches. When you hit "RETURN" it's obviously lost track of where the
head is, and slams it into the left-hand stop, where it sits obstinately
pressed against the spring.
Cleaning up the photosensor bit on the interrupter wheel seemed to help
a little.
I thinkl you're in the right area. I would grab the prints and look at
that circuitry, stick a 'scope on the outputs of the phototransistor
amplifiers, etc.
Oh, and do check the power lines for mains ripple!
-tony
29 Jan
29 Jan
11:35 p.m.
New subject: Solved: Jittery LA36
Hi there,
I've finally got the ribbons for my LA36, unjammed the pins in the
printhead and it is printing. It's not quite right yet, though...
As a couple of you pointed out, adjusting the tacho on the end of the
carriage drive motor did the trick. It would have been easier if my
sillyscope hadn't expired just as I was about to start, but I got there in
the end.
What I did in the end was determine where the "worst" points were by
listening to the bump as it skipped up and down (the original fault) and
set the pickup position around the middle. Then it took a tiny tweak of
one of the sensor bias pots to take a little tick about half-way up out of
it. Now it's lovely and smooth.
Now, next question. Anyone got a service manual for a Scopex 4D25?
Gordon.
6901
days inactive
6907
days old
4 comments
3 participants
participants (3)
-
ard＠p850ug1.demon.co.uk -
gordonjcp＠gjcp.net -
jwstephens＠msm.umr.edu