ASR33 Problems

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Tue Nov 12 16:07:00 2002

>From: "David Comley" <david_comley_at_yahoo.com>
>
>>Hi
>>I think you need to make this point clearer. When a
>character
>>is punched, the same character is miss printed on the
>platen?
>>This is how I read his original post.
>
>Even using the REPT key to workaround the codebar
>issue, I wasn't able to connect the carriage problem
>conclusively to either a rotational or a vertical
>problem. I think at this point I'm going to take the
>carriage off again and try a more thorough
>dismantle/clean/oil. Once I resolve the codebar issue
>it will be easier to diagnose the carriage problem
>with a clean mechanism.
>
>>This tells me it is something sticking in the linkage
>that goes
>>between the code bars and the print head( or he has
>it installed
>>wrong but that doesn't explain why it starts working
>with repeats ).
>>I would remove the print assembly and put it in some
>solvent
>>while moving the levers. Then clean it off/dry it and
>re-oil
>>it. You most likely have some dry oil that is
>sluggish. Getting
>>oil into the right place will take a bit.
>>In the service( military ), we used to clean things
>in a bath
>>of water and heavy detergent. This was done in an
>ultrasonic
>>cleaner. We'd then rinse and bake it at about 150F
>for a few
>>hours. Then Re-oil/grease, place on test bench and
>fine adjust.
>>I suspect that a good dish washing liquid would work.
>
>I remember using an arklone bath at a place I worked
>years ago for cleaning circuit boards. Probably taken
>a few years off my live expectancy breathing that
>stuff in.
>
>>
>>Basically, there are 3 possible problem areas :
>>
>>1) The keyboard contacts are not closing correctly,
>so the parallel data
>>output of the keyboard is incorrect.
>>
>>2) The distributor disk (rear right of the typing
>unit) is not correctly
>>serialising the data from the keyboard. Unlikely, but
>possible.
>>
>>3) The selector unit (rear left of the typing unit)
>is malfunctioning,
>>and is not correclty responding the receiving magnet.
>>
>
>I can see the armature 'stutter' when I punch the
>rubout key - by stutter, I mean that its movement
>looks slightly different between keypresses. So I'm
>inclined to think that the magnet is just responding

Hi
 You haven't made it clear about punching. Does it work
correctly when you use the punch?? If it does, it can't
be the keyboard, distributor or codebars. All of these must
work to have the punch work correctly. The punch is
mechanically connected to the code bars of the printer.

>to what it is receiving which is incorrect. I cleaned
>the distributor and reseated the brushes, readjusted
>the brush holder to the alignment mark per the
>adjustment procedure in the manual. So I'm back to
>option 1) - the keyboard - as the source of the
>problem. One thing I noticed last night was that the
>keyboard cover is broken. There are four round tabs,
>one at each corner, that fit into corresponding holes
>on the end plates. These are broken, so the cover can
>rock from side to side, pivoting on those center
>projections. I wonder if that could cause some sort of
>alignment problem within the keyboard ?

 I'd think it would have to shift quite a bit to fail.
It would be more likely that the switch contacts( at the
right side of the keyboard ) might be dirty.
 For the pegs, one can drill the plastic and use some
dowel rod( wood or plastic ) from the hobby shop to
replace the alignment pegs. Since this had a punch on it,
it most likely has a lot of chad stuck on things that can
gum things up.


>
>Thanks for the suggestions - I will get to it again
>tonight and see what else I can find out. I hate the
>idea of opening that keyboard up...

 As I stated earlier( in this group ), you can disconnect
the power from the motor and run things slowly to see what
is missing. You just have to manually lock up the clutches
since it isn't spinning fast enough to lock them with inertia.
Dwight

>
>Dave
>
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Received on Tue Nov 12 2002 - 16:07:00 GMT

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