[GreenKeys] UPDATE- shockingly basic question - Teletype Model 33 ASR

Thu Feb 11 11:20:51 EST 2021

>
> Do you have access to an ASCII code chart?  If not, I can send you a
> photo.
>

*Yes I do ... I always wondered what it was for haha 😁*

Try pressing a single character on the keyboard repeatedly and not when the
> character prints incorrectly.  If there is AC ripple on the DC supply to
> the selector magnets, you will see random characters but the random
> characters are caused by the lack of a pure DC supply.  The AC ripple
> imposed on the DC current will cause random bits to be added to the
> original character as processed by the selector magnets.
>

*Well that makes sense. Looking at my ring binder (Tech bulletin 310B Vol2)
I have a power supply circuit diagram, but I am not sure where I would
physically plug in my highly underused budget Hantek scope...*

For example, the letter A is created by a bit in the 1 position and another
> bit in the 7 position.  Say you type A and you get C occasionally... that
> is because the selector magnets saw bits in positions 1, 2 and 7.  The
> extra bit, in the second position, was added by the AC ripple on the DC
> going through the magnets.
>
> Crystal clear or clear as mud?
>

*Yep I think I get the general idea and I am excited to diagnose but I warn
you I am out of my league here but very enthusiastic! (famous last words
🤓)*

On Wed, Feb 10, 2021 at 5:53 PM Russ Miller <wa3frp at gmail.com> wrote:

> Andy,
>
> Not difficult to find out!  Do you have access to an ASCII code chart?  If
> not, I can send you a photo.
>
> Try pressing a single character on the keyboard repeatedly and not when
> the character prints incorrectly.  If there is AC ripple on the DC supply
> to the selector magnets, you will see random characters but the random
> characters are caused by the lack of a pure DC supply.  The AC ripple
> imposed on the DC current will cause random bits to be added to the
> original character as processed by the selector magnets.
>
> For example, the letter A is created by a bit in the 1 position and
> another bit in the 7 position.  Say you type A and you get C
> occasionally... that is because the selector magnets saw bits in positions
> 1, 2 and 7.  The extra bit, in the second position, was added by the AC
> ripple on the DC going through the magnets.
>
> Crystal clear or clear as mud?
>
> Russ
>
> Sent from my iPhone
>
> On Feb 10, 2021, at 5:37 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>
> 
> Thanks Russ... although I am not going to lie, I have no idea if I am
> gaining or losing 😳
>
> On Feb 10, 2021, at 4:47 PM, Russ Miller <wa3frp at gmail.com> wrote:
>
> Andy,
>
> If you are gaining data bits, put a voltmeter on the DC supply to the
> magnets to see how much AC is present.  The 1500 mf capacitor is a common
> failure point in these older machines.
>
> Russ WA3FRP
>
> Sent from my iPhone
>
> On Feb 10, 2021, at 4:14 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>
> 
> Hey Wayne - thx for the info!
>
> Apologies I was not so precise in my description: When I apply power (in
> the OFF position) the buzzing starts. It's quite loud and at the rear of
> the machine.
>
> When I go into LOCAL or LINE, I get the garbled characters.
>
> Check out my tiny video     https://www.youtube.com/watch?v=Ri42KBN6kPM
>
> cheers!
> Andy
>
> On Wed, Feb 10, 2021 at 2:40 PM WAYNE <teletypeparts at comcast.net> wrote:
>
>> Andy,
>>
>> The trouble is the smaller electrolytic capacitor in the front of the
>> UCC-6.  Just in front of the large green multi-tap resistor.   250 MFD at
>> 75VDC.  Very common trouble.
>>
>> I have a couple used ones but you might want to order a new one from
>> Mouser.  I think I would get 2 so you would have another for the second
>> 33.
>>
>> Also the 1500 MF at 30VDC electrolytic that lays behind the SMD card will
>> cause a buzzing when you push the armature open with power plugged in and
>> 33 in OFF position.
>>
>> But loud buzzing when power plugged in is definitely the smaller cap.
>>
>> 73,
>>
>> Wayne
>>
>>
>>
>> On 02/09/2021 8:47 PM Andy KN4UCL <kn4ucl at gmail.com> wrote:
>>
>>
>> I removed the SMD card and took a photo (see attached) and all looks
>> visually OK.  Before swapping with the other one I popped it back in just
>> to make sure things were as before... but yikes!  Quite a buzzing sound in
>> Line or Local.  Line was no longer working and Local would not type very
>> faithfully. Buzzing did not stop so I quickly powered off, and when I did
>> there was a gentle mechanical  'pop' as the power released. I removed and
>> repositioned the card ... but same symptoms.
>>
>> Thought I'd better power off before something starts burning!
>>
>> On Tue, Feb 9, 2021 at 7:21 PM Michael Katzmann < vk2bea at gmail.com>
>> wrote:
>>
>> Try swapping the selector magnet driver card between the two units. (
>> vertical card on the right hand edge). If you are having problems in local
>> then it is not the RS232-current loop circuit but it might be the magnet
>> driver.
>>
>> On Tue, Feb 9, 2021 at 4:53 PM Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> So RIGHT NOW the machine is running great, just like in the video from
>> 1:42s  onwards.  It also prints perfectly in Local mode as well right now,
>> no matter how fast I try to type.
>>
>> However - it will intermittently go back to garbage output, as is shown
>> prior to 1:42s in the video.
>>
>> When I was testing in Local last night it was OK typing slowly, but
>> typing a little fast caused garbage output.
>>
>> So I think the terminal is intermittently behaving badly, in LIne and
>> Local.
>>
>> But.. of course... right now it is behaving itself!
>>
>> cheers
>> Andy
>>
>>
>>
>> On Tue, Feb 9, 2021 at 2:21 PM Michael Katzmann < vk2bea at gmail.com>
>> wrote:
>>
>> I don't see this as a parity issue. I would expect the ASR33 typing unit
>> to ignore parity on receive. Although, I think the tape punch will punch
>> the eighth bit (or parity) if received.
>> Likewise the tape reader will read and send all eight bits.
>>
>> Does the ASR read a tape and print consistently in local ?
>> I'd be suspicious of the RS232 converter. If you have an oscilloscope and
>> can look at the RS232 input compared with the current loop output it may
>> prove or dispel this hypothesis.
>>
>> Michael
>>
>> On Tue, Feb 9, 2021 at 1:22 PM Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> Well I was hoping that it was either my serial loop adapter acting up, or
>> a cabling-from-serial-converter-to-terminal-server problem.  I've replaced
>> everything (including the terminal server) but sadly no obvious fix.
>>
>>    https://www.youtube.com/watch?v=h-w-HCXI25E
>>
>> I've got two similar 33s (both no parity keyboards) and I've had them
>> both running at the same time connected to my terminal server for a while
>> now.  Recently I get very garbled data on one of them. It doesn't seem to
>> be related to the connected equipment or cabling as I've replaced
>> everything.
>>
>> Then... very weirdly it starts working again, as you can see  at 1:42s on
>> the video.
>>
>> Apart from fiddling about with the rangefinder, any other thoughts about
>> (simple 😁) tests or adjustments I can make to diagnose this?
>>
>> thanks folks.
>> Andy
>>
>> On Thu, Feb 4, 2021 at 3:33 PM Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> OK well this is all very embarrassing. I have two almost identical 33s
>> (both non-parity) .... the other one works great connected to my Terminal
>> Server so thought I'd better  swap the RS232 Adapters, port and cable.. and
>> hey presto - my "not working due to parity errors" Teletype started running
>> fine!
>>
>> I then swapped back to the original RS232 adapter, cables and port...
>> expecting things to NOT work... but of course, everything ran fine (sigh.)
>>
>> I've tried jiggling the cables (I was hopeful maybe a weird cable problem
>> could be the issue) but I am struggling to see how a wiring problem would
>> look like a legit parity problem.
>>
>> Anyway! All good for now.. but I am curious what would cause these
>> parity-like symptoms. I am going to replace the cables anyway, and probably
>> grab another RS232 converter just in case.
>>
>> cheers!
>> Andy
>>
>> On Wed, Feb 3, 2021 at 11:05 PM Mike Douglas < deramp5113 at yahoo.com>
>> wrote:
>>
>> Since you are concerned about the parity of your keyboard while testing
>> the TTY printing function, I assume your terminal server is in a mode where
>> it echos characters that you type on the TTY keyboard back out to the TTY
>> printer and you are testing your printer by typing on the TTY keyboard?
>>
>> If this is what you’re doing and you have a non-parity keyboard, then set
>> the serial port to 7 data bits plus mark parity (non parity keyboards set
>> the 8th bit to one). This should ensure the server accepts the typed
>> characters. If you type one character at a time with a short pause between
>> each character, then each character should echo properly to the TTY
>> printer. The pause between each character will be more than the two stop
>> bits the printer requires (and the printer ignores the 8th bit).
>>
>> If, however, you have a telnet session open and are sending data from a
>> remote device to the TTY printer and are not using the TTY keyboard to
>> generate test data, then set the serial port to 8 data bits plus mark
>> parity. This will appear as 8 data bits and 2 stop bits to the printer (as
>> it requires) and the printer can then keep up with a steady stream of data.
>>
>> If you are getting some garbage characters with either of these methods
>> but everything prints correctly in local mode, you made need to adjust the
>> rangefinder a bit.
>>
>> Mike
>>
>> On Feb 3, 2021, at 9:22 PM, Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> My Teletype has a Deramp converter which goes direct into an Equinox
>> ELS-16 terminal server.  When I start I get a session with the terminal
>> server and can interact directly with the server ... or telnet onwards
>> elsewhere.
>>
>> On Feb 3, 2021, at 10:00 PM, Mike Douglas < deramp5113 at yahoo.com> wrote:
>>
>> I guess I’m confused as to your test setup then. What is sending data to
>> your Teletype? Is it coming from an external source other than the
>> Teletype, or are you testing by somehow looping keyboard input from your
>> TTY back out to the TTY printer?
>>
>> Mike
>>
>> On Feb 3, 2021, at 8:36 PM, Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> I think I am still missing a trick or two here...I tried every
>> combination of 8 and 7 even/odd/none/mark/space and I get no printing at
>> all with 8 bit, but moderately bad spelling errors with 7.  See attachment
>> below... presumably this means I have the non-parity keyboard?
>>
>> thanks in advance for your thoughts!
>> Andy
>>
>> On Sun, Jan 31, 2021 at 8:18 PM Mike Douglas < deramp5113 at yahoo.com>
>> wrote:
>>
>> If you select 8 bit with mark parity on your terminal server, you’ll
>> probably get the 8N2 timing the Teletype requires (the mark parity bit
>> serves as the first stop bit).
>>
>> Mike
>>
>> On Jan 31, 2021, at 7:11 PM, Andy KN4UCL < kn4ucl at gmail.com> wrote:
>>
>> Thanks guys for the responses - a lot of great info for me to digest!
>>
>> My terminal server (Equinox ELS-16) allows me to define character size as
>> 7 or 8 bits, and to set parity as NONE, ODD, EVEN, MARK or SPACE.
>>
>> I don't seem to have the ability to specifically state the number of stop
>> bits, however.
>>
>>
>> Anyway.. I'm going to crack my Teletype open and confirm exactly what's
>> going on.
>> cheers!
>> Andy
>>
>> On Sun, Jan 31, 2021 at 5:43 PM Keith Lueck < kwlueck at swbell.net> wrote:
>>
>>
>> Jim & Wayne are spot-on, of course.  I learned the hard way that you best
>> include the parity bit - even though the 33 doesn't give a whit about
>> parity...
>> My machine was occasionally producing errors when I was feeding it 7 N
>> 2.  Wayne Durkee set me straight, and, viola, when I sent it 7 M 2,
>> everything was 100% ducky.
>>
>> On Sunday, January 31, 2021, 03:32:30 PM CST, Jim Haynes <
>> jhhaynes at earthlink.net> wrote:
>>
>>
>> All the 33s and 35s generate 11 unit code.  1 start bit, 7 data bits, one
>> bit which may be even parity or may be marking, and two stop bits.
>> That's
>> where 110 baud comes from. 100 wpm = 10 chars/sec and each char contains
>> 11 bits.  The reason for two stop bits is the difficulty of making a
>> mechanical selector that is reliable at 100 wpm.
>>
>>     ---
>>
>>     "Ya can argue all ya wanna, but it's dif'rent than it was."
>>     "No it ain't! No it ain't!  But ya gotta know the territory."
>>         Meredith Willson, The Music Man
>>
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>>
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>> <non parity keyboard.png>
>>
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>>
>>
>>
>>
>>
>> --
>>    |\      _,,,---,,_             Michael Katzmann
>>    /,`.-'`'    -.  ;-;;,_         NV3Z / VK2BEA / G4NYV
>>   |,4-  ) )-,_. ,\ (  `'-'
>>  '---''(_/--'  `-'\_)             vk2bea at gmail.com
>>
>>
>>
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>>
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>
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>
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>
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>
>
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