[GreenKeys] UPDATE- shockingly basic question - Teletype Model 33 ASR
Russ Miller
wa3frp at gmail.com
Thu Feb 11 11:47:38 EST 2021
Very cool! Digging into the details is always fun.
On Thu, Feb 11, 2021 at 11:21 AM Andy KN4UCL <kn4ucl at gmail.com> wrote:
> 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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>>> <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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