[GreenKeys] Model 14 keyboard adjustment

Sun Aug 6 13:55:29 EDT 2023

Attached is the waveform, and the decoder receiving the R in slow mo.

-Eric

On Sun, Aug 6, 2023, 12:33 PM Eric Moore <mooreericnyc at gmail.com> wrote:

> I went at it again and am now getting a lovely waveform. I did use some
> 3000 grit sandpaper, but very lightly just to break up the surface a bit
> with a generous application of contact cleaner
>
> I dialed in the timing, and got a perfect R on the decoder in loopback! I
> am also getting lots of extraneous characters, so going to disable loopback
> while I work on the printer, but still, progress.
>
> Next, my vertical drive for the printer is not moving the full cycle
> vertically, again. It is a symptom of a bad bend around the code arms this
> printer suffered, and mis-alignment on the vertical printer cam arm.
>
> I am afraid I may need to disassemble for the umpteenth time to adjust the
> printer, again, again, again...
>
>
> -Eric
>
>
>
> On Sun, Aug 6, 2023, 9:47 AM Mike Douglas <deramp5113 at yahoo.com> wrote:
>
>> Note that the loop adapter Eric is using has separate printer and
>> keyboard loops and Eric has those loops wired separately on his Model 14.
>>
>> The printer loop has flyback capture onto a storage cap, along with a
>> switching voltage boost option to generate the high voltage and quick
>> switching times required by the high inductance selector magnet loops of
>> the Model 14 and 15 era machines.
>>
>> The keyboard loop on this era of machine has to simply sense switch
>> closures. Over a short loop (like we have in our labs), and given contacts
>> in good condition, 15v is plenty to reliably test closure of the keyboard
>> distributor contacts. A higher voltage does not “clean” the contacts, but
>> instead, results in an arc that can briefly conduct through a layer of
>> oxidation or oil film. The conduction, however, might be only for the
>> instant of the arc (as you see in Eric’s video). In this case, the bit is
>> still sensed incorrectly. The arc can also clear enough oxidation or oil
>> away that then that spot continues to make low resistance contact while
>> mechanically closed. In this case, the bit is sensed correctly. The problem
>> with “cleaning” with high voltage is that each arc creates more damage to
>> the contact surface and also creates its own burn residue that, in turn,
>> raises contact resistance.
>>
>> I’d continue to work on the contacts with paper tape or a business card
>> whetted in contact cleaner. Move the paper back and forth while you apply a
>> bit of pressure to close the contacts against the paper and each other. The
>> keyboard contacts on my Model 15 took quite a bit of work, but I was
>> eventually able to get them under 1 ohm.
>>
>> On a “modern” model 33, the distributor is a carbon wiper with at least
>> 40 ohms of resistance, and even there, just 12 volts in keyboard loop
>> current is reliable for reading the keyboard electronically.
>>
>> Mike
>>
>> On Aug 6, 2023, at 8:44 AM, Eric Moore <mooreericnyc at gmail.com> wrote:
>>
>> 
>> Thanks all, makes sense. I am using deramps adapters, and I am fairly
>> certain that if I can remove the deep layer of gunk/oxides/whatever that
>> formed over many decades of shed storage on these contacts that were open,
>> it will work great on the low voltage circuit.
>>
>> I say that because the start bit contact works beautifully. It is the
>> other 5 contacts that were left open to the air (were mechanically open
>> when stored badly) that I am having trouble with.
>>
>> I bet a good shot of high voltage would help, I have a high voltage
>> supply out in the shed I may bring in. I expected the contact cleaner to
>> chemically remove the problematic materials when combined with my
>> mechanical cleaning, but apparently not.
>>
>> -Eric
>>
>>
>>
>>
>> On Sun, Aug 6, 2023 at 8:33 AM Paul Heller <paul0926 at comcast.net> wrote:
>>
>>> It was around 2009:
>>>
>>> [GreenKeys] why high loop voltage
>>> <http://mailman.qth.net/pipermail/greenkeys/2009-January/013324.html>
>>> mailman.qth.net
>>> <http://mailman.qth.net/pipermail/greenkeys/2009-January/013324.html>
>>> <favicon.ico>
>>> <http://mailman.qth.net/pipermail/greenkeys/2009-January/013324.html>
>>> <http://mailman.qth.net/pipermail/greenkeys/2009-January/013324.html>
>>>
>>>
>>> Paul
>>> W2TTY
>>>
>>> ITTY: HTTP://INTERNET-TTY.NET:8000/ITTY
>>> <HTTP://internet-tty.net:8000/ITTY>
>>> ITTY 100:  HTTP://INTERNET-TTY.NET:8010/ITTY100
>>> AUTOSTART: HTTP://INTERNET-TTY.NET:8030/AUTOSTART
>>> <HTTP://internet-tty.net:8030/AUTOSTART>
>>> EUROPE: HTTP://INTERNET-TTY.NET:8040/EUROPE
>>> <HTTP://internet-tty.net:8040/EUROPE>
>>>
>>> On Aug 6, 2023, at 7:31 AM, Paul Heller <paul0926 at comcast.net> wrote:
>>>
>>> I remember a discussion years ago where a number of folks said high
>>> voltage was important for the contacts. The design voltage was much higher
>>> than 15v. You might try a loop source that delivers higher voltage and
>>> 60ma. That might work better with your contacts.
>>>
>>> Paul
>>> W2TTY
>>>
>>> ITTY: HTTP://INTERNET-TTY.NET:8000/ITTY
>>> <HTTP://internet-tty.net:8000/ITTY>
>>> ITTY 100:  HTTP://INTERNET-TTY.NET:8010/ITTY100
>>> AUTOSTART: HTTP://INTERNET-TTY.NET:8030/AUTOSTART
>>> <HTTP://internet-tty.net:8030/AUTOSTART>
>>> EUROPE: HTTP://INTERNET-TTY.NET:8040/EUROPE
>>> <HTTP://internet-tty.net:8040/EUROPE>
>>>
>>> On Aug 6, 2023, at 7:27 AM, Jeffrey Golas <jeffg at junknet.net> wrote:
>>>
>>> 
>>> Dont use sandpaper! The MA is important as it does affect the waveforms.
>>> The machine wants to see 60ma whether it's 120vdc or 15vdc. Set the scope
>>> to be wide enough to get an entire character if you havent already, it
>>> almost looks like the pic may just be showing the stop bit (33ms?).
>>>
>>> Dial in the loop first, verify its 60ma at idle.
>>>
>>> Jeff
>>>
>>> On Aug 6, 2023, at 9:05 AM, Eric Moore <mooreericnyc at gmail.com> wrote:
>>>
>>> 
>>>
>>> https://deramp.com/downloads/teletype/Model%2015/loop%20interface%20board/Schematic%20Rev%20A.pdf
>>>
>>> Verified the printer loop at 60ma. The keyboard loop runs at 15V, not
>>> sure on the ma, but not sure it matters much as it just opens and closes
>>> without driving any coils or similar.
>>>
>>> I am fairly certain my issue is the contacts somehow. I see voltage (and
>>> continuity) up to those contacts, but despite cleaning fairly extensively
>>> with contact cleaner, they are still too high resistance. I am going to try
>>> some sandpaper today and see what is what...
>>>
>>> -Eric
>>>
>>> On Sun, Aug 6, 2023, 12:10 AM Gerry Block <gblock at sbcglobal.net> wrote:
>>>
>>>> typo:  "60 ma"
>>>>
>>>> Sent from my iPhone
>>>>
>>>> On Aug 5, 2023, at 10:07 PM, Gerry Block <gblock at sbcglobal.net> wrote:
>>>>
>>>> eric
>>>>
>>>> what does your loop schematic look like?  sketch it out and enclose
>>>> photo.
>>>> what is the loop power supply voltage.
>>>> what is the series resistance to make the 60ms.
>>>> are you sure it is running at 60 ms?
>>>> where is the scope probe grounded and where is the loop supply grounded?
>>>> i doubt it is the contacts.
>>>>
>>>> gerry
>>>>
>>>> Sent from my iPhone
>>>>
>>>> On Aug 5, 2023, at 5:49 PM, Eric Moore <mooreericnyc at gmail.com> wrote:
>>>>
>>>> 
>>>> I have cleaned with contact cleaner and paper tape pretty extensively,
>>>> but can always go another round.
>>>>
>>>> I do not think that is a good waveform, but similarly, no idea.
>>>>
>>>> -Eric
>>>>
>>>> On Sat, Aug 5, 2023, 7:23 PM Jeffrey Golas <jeffg at junknet.net> wrote:
>>>>
>>>>> Correct me if Im wrong but could just be "dirty"; as the cam rubs
>>>>> against the switch youre seeing noise like a dirty volume pot.
>>>>>
>>>>> Id use some alcohol and a business card and scrub the contacts (plus
>>>>> Im not sure thats even a terrible signal for a 1940s device. Going machine
>>>>> to machine I dont think that tiny bit of leakage woulda mattered.
>>>>>
>>>>> Again, correct if wrong, Im here learning too.
>>>>>
>>>>> Jeff KC3GJX
>>>>>
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>>
>> 2002-to-present greenkeys archive:
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>>
>> 1998-to-2001 greenkeys archive:
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>>
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>>
>>
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>> Please help support this email list: http://www.qsl.net/donate.html
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