DECwriter Correspondent (LA12) mechanical issue...

[Josh Dersch]

On Mon, Nov 10, 2014 at 3:00 PM, Josh Dersch <derschjo at gmail.com> wrote:

> Thanks a ton for going through the trouble on this, it's much appreciated.
>
> I'll have to go through mine and see if that clip somehow ended up wedged
> somewhere inside.  Otherwise, I guess it can't be too hard to build a
> replacement.
>
> Thanks again!
> Josh
>

Just a quick update on this -- I opened the Correspondent up and went
through it with a flashlight and found the clip wedged in a rear corner,
behind some wiring.  It had at some point gotten ripped off the underside
of the carriage (along with most of the plastic post it was screwed to).  I
glued it back into place and the terminal is operating much better now but
still has some issues -- when the carriage reaches either end of the platen
it starts twitching rapidly back and forth and the terminal stops
responding to input.  It sounds like some sort of sensor issue, perhaps the
logic is confused about exactly where the carriage is.  Time to do some
debugging, I suppose :).

Thanks again,
- Josh



>
>
> On Mon, Nov 10, 2014 at 7:39 AM, Simon Claessen <simski at dds.nl> wrote:
>
>> hey there,
>>
>> Today I got some time to take a look at our correspondent and guess what,
>> there should be a brass clip to hold the ball:
>>
>> https://hack42.nl/gallery/v/Museum/2014-11-10-693.jpg.html
>>
>> I could not take the clip off. wiggling it also moved the spring holding
>> the print needle block.
>>
>> simon
>>
>>
>> On 07-11-14 18:55, Josh Dersch wrote:
>>
>>> Hi all --
>>>
>>> Got myself a nice looking DECwriter Correspondent (AKA the LA12). It's
>>> having a bit of trouble moving the carriage assembly and I can't find a
>>> service manual for this thing.  (It's similar in some respects to the
>>> DECwriter IV, but the mechanical parts appear to be fairly different.)
>>>
>>> The carriage assembly (print head, ribbon) is carried from one end of
>>> the platen to the other via a cable attached to a servo motor on one end
>>> and a pulley on the other; in the middle of this cable is a small metal
>>> ball -- this ball is (as far as I can tell) meant to sit in a small
>>> "cup" on the underside of the carriage and when the cable moves, the
>>> ball pulls the carriage along.  I'm assuming this was done this way
>>> since the Correspondent is meant to be portable, and allowing the
>>> carriage to break free of the pulley mechanism would probably reduce
>>> damage in the case of a sudden shock (like getting dropped.)
>>>
>>> So far so good -- unfortunately the vast majority of the time, the ball
>>> leaves the carriage behind (especially on carriage return) and I can't
>>> quite figure out what's out of tolerance -- the carriage appears to move
>>> smoothly, nothing is bent out of shape or broken as far as I can tell,
>>> and there's plenty of tension in the cable.  There's also not much to
>>> adjust here so I'm kind of puzzled.
>>>
>>> I've put up a few pictures (and a short video demonstrating the problem)
>>> with the print head/ribbon removed here:
>>>
>>> http://yahozna.dyndns.org/scratch/la12
>>>
>>> Anyone ever worked on one of these before?  Any ideas?
>>>
>>> Thanks as always,
>>> Josh
>>>
>>>
>> --
>> Met vriendelijke Groet,
>>
>> Simon Claessen
>> drukknop.nl
>>
>
>