Jittery LA36 - test-drb@ccmp.vtda.org

27 Jan 2006

Gordon JC Pearce gordonjcp at gjcp.net
Tue Jan 24 14:22:27 CST 2006
...

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.

Hi,

Test the free movement of the carriage when powered down and lubricae with
some sewingmachine oil on the guidance bars, between the printhead bearing.
There must be a resonable free movement.

Then adjust the sensor allignment at the carriagemotor, you will need a
dual channel scope connected to two test points on the logic board, as
discribed in the maintenance manual. I'am pretty sure the jitter is caused
by a misallignement, as I have fixed dozens of LA36 for this.

Unfortunately, I do not have any docs anymore, but to do the allignement
you have to:

1. Release the tension spring and remove the rubber belt from the motor.
2. appley constant power to the carriage motor. (To generate many pulses).
   (don't remember if 5 or 12 volt, but it is discribed in the maint.man.).
3. Loosen the screws holding the sensor a bit so you can move it.
4. Position the sensor such, that the time-shift between the two pulses
   from the sensor on your scope has the required value (15 ms?).

I dont remember the values, but that's in the books. It sounds complicated,
but it is actualley a very simple adjustment. Given the fact that I never
screwed it up... :-)  But you need a scope.

Succes,
Frank