Jittery LA36 updated

[Gordon JC Pearce]

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.