[GreenKeys] Model 33 Progress

[Brad]

I did a bit more experimenting last night.  I tried temporarily pulling out
one contact wire at a time so that it could not make any contact.  One of
them, once pulled out, caused the type unit to move the carriage with each
key press.  It also caused some characters that had been wrong to come up
right.  So I'm back to thinking something to do with the keyboard.  

I think I sort of get how it works.. the base of the contact wire touches a
contact at the bottom.. and then the tops of the contact wires complete or
break a circuit.  So hitting a key will cause a pattern of connected and
broken contacts and that I guess is your matrix decoding that tells the
print unit what to print.  

I think contacts are not being made properly.. so some keypresses don't
generate enough of a signal to produce a letter while others do.  I've
observed the plastic sliders that control contact sometimes seem like they
are still leaving gaps up top where contact looks like it should be made.

It moves pretty fast though so its hard to tell.  I am trying to find a
matrix or something that I can use to somehow check contacts for different
keys.  I wonder if I can set a key without power and check continuity.. I do
notice that when the machine is running contact wires seem to briefly get
pulled against the strip.  Don't think they'll do that with no power.

-----Original Message-----
From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of
Ralph Mowery
Sent: Tuesday, November 8, 2016 6:52 AM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Model 33 Progress



> -----Original Message-----
> From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf 
> Of Jeffrey D Angus
> Sent: Tuesday, November 08, 2016 4:28 AM
> To: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] Model 33 Progress
> 
> On 11/8/2016 12:18 AM, drlegendre . wrote:
> >
> > For reference, this is where ESR meters (Capacitor Wizard, the Blue 
> > Meter, etc.) or other so-called "in-circuit cap testers" can come in 
> > very handy.
> Or...You can not waste your time testing 40-50 year old parts that are 
> known to fail, and that will fail eventually, and just replace them.
> 
> 
> 
Usually I don't like to shotgun the equipment, but I agree.  When something
is not working correctly that has the electrolytic capacitors in it, just
replace them all.  They may not be bad, but could be and if they do go bad
while working on a problem you will chase things all around.


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