[GreenKeys] How hot is too hot? (Teletype 32)

Tue Sep 6 19:36:00 EDT 2022

Good evening/morning folks!  After wasting a good amount of time on a blown
fuse in my low-grade multimeter, I finally managed to measure the  current
between the Teletype and the i-Telex. Below are my findings

Teletype + i-Telex powered on: *4 mA (*Dial lamp illuminated - motor starts
to run but does NOT run "open")

If I press STOP button on Teletype: *58mA *(Dial lamp extinguished)

Similarly, if the Dial Lamp is illuminated, and if I try and dial a number
- the motor switches off very quickly.

And finally - if I press the Test button on my i-Ttelex, the motor spins up
and shuts down after about 7 seconds (no printing.)

Thank you for your guidance!
Andy

On Tue, Sep 6, 2022 at 11:03 AM Andy KN4UCL <kn4ucl at gmail.com> wrote:

> Hey Paul I have the single TW39 card... ummm let me see if I can use my
> multimeter to measure the current 😱😊
>
> On Tue, Sep 6, 2022 at 10:34 AM Paul Heller <paul0926 at comcast.net> wrote:
>
>> In my case the resistor mods were not enough. I never understood why, nor
>> did Russ. It still drew way too much current and I blew up the TW39 port.
>> Do you have a dual TW39 card? Maybe try the other port?
>>
>> I had to add additional resistance in the loop to get the current down to
>> 40ma.
>>
>> Be sure to measure your loop current and keep it around 40ma.
>>
>> Paul
>> W2TTY
>>
>> On Sep 6, 2022, at 4:22 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>>
>> 
>> Thanks guys for the helpful responses!  I am ashamed to admit that after
>> an excellent chat session yesterday (with the cover off - keep things cool)
>> my beloved 32 no longer properly wakes up when I receive a message or send
>> a test message from the i-Telex!  The motor runs, but no typing.  After
>> about 7 seconds it shuts down. I wonder if I disturbed something removing
>> the cover, or maybe my resistor modifications finally broke something
>> 😳😱... iTelex seems fine as I can see messages coming in overnight by
>> looking at my TW39 serial port in tera term. cheers!  Andy
>>
>>
>>
>> On Tue, Sep 6, 2022 at 6:56 AM Joe Duszyński <joeduszynski1 at gmail.com>
>> wrote:
>>
>>> For the i-Telex,
>>> Better yet use a Diode and a momentary push button in parallel to
>>> short out the diode to dial out.
>>> You hold the button down while you dial the number and release the
>>> button when the current reversal happens,
>>> then the power consumption is Zero at idle. Fancy relays.... BAH!! LOL!
>>>
>>> 99% of the time the machine sits idle with i-Telex (unless you call out
>>> a lot).
>>> The diode will not affect the current reversal.
>>> If you have a machine that "only" sits on a subscription service and
>>> never dials out on I telex like I do,
>>> you don't even need the switch just the diode because all you are
>>> doing is waiting on a call (Current reversal).
>>>
>>>
>>> I made an "el cheapo" FSG for a machine without one, using a diode,
>>> momentary push button,
>>> a 100ohm resistor, optocoupler, a phone dial and a countdown timer
>>> relay set for 2 seconds.
>>> Even put it in a fancy 3d printed potted box with wiring terminals and
>>> everything! ;-)
>>>
>>> When the reversal happens the optocoupler trips and holds the timer
>>> relay, since the relay is set for 2 seconds the pulsing on and off of
>>> the message does not affect the relay and when the current reverses
>>> back to hang, up the relay shuts off in 2 seconds.
>>> When you hold the momentary push button down (only hooked across the
>>> diode not the optocoupler) you get full loop current to the dial and
>>> the motor stays off.
>>> If you want the schematic to make an FSG for a machine without one, I
>>> can send it.
>>> The one I built has been running 24/7 since April or May of this year.
>>>
>>>
>>> Some ITELEX FYI.....
>>> The i-Telex doesn't "look" for the really low idle current like a real
>>> telegraph exchange.
>>> In a real telegraph exchange there needs to be a really low idle
>>> current of around .004 ma.
>>> The i-Telex does provide this very low current but it does not look
>>> for it to exist. The i- Telex only cares that
>>> the current flow is lower than its threshold to register as an off
>>> condition. The i-Telex does not care if the current is present or if
>>> it exists at all.
>>>
>>> The i-Telex actually only looks for the circuit to go open or closed
>>> because the optocoupler can only sense "ON" and "OFF"
>>> The high impedance "low current" state of the FSG is the same to the
>>> i-Telex as an open circuit, it is sensed as an OFF state.
>>> The circuit is such that the really low draw won't activate the
>>> optocoupler.
>>>
>>> The i-Telex mimic's the operation of an exchange rather well but if
>>> you have a FSG that the high impedance relay draws slightly too much
>>> current
>>> the optocoupler then activates and the i-Telex will think the
>>> teleprinter has gone "off hook" and cause problems, in this case you
>>> have to add some resistance to
>>> the relay or if its circuit is adjustable "Adjust it" to negate the
>>> excess current draw and that can be a balancing act with an old
>>> finicky FSG.
>>>
>>> "The more you know"
>>>
>>> JD
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Sep 6, 2022 at 4:25 AM Paul Heller <paul0926 at comcast.net> wrote:
>>> >
>>> > This is a good idea - stand the resistors off of the board as much as
>>> possible. Why not?
>>> >
>>> > Paul
>>> > W2TTY
>>> >
>>> > On Sep 6, 2022, at 10:14 AM, Henning Treumann via GreenKeys <
>>> greenkeys at mailman.qth.net> wrote:
>>> >
>>> > 
>>> > European (or better non Teletype) machines use a very sensitive
>>> polarized relay to detect
>>> > the current loop reversing of the TW39 system which switches the motor
>>> power relay after
>>> > an incoming call.
>>> > Hence stand-by power usage of an European Telex control unit is almost
>>> nothing.
>>> >
>>> > I would install the mentioned resistors on a small distance to the
>>> PCBs.
>>> >
>>> > And yes... it should be online 24/7 - that's the fun of i-Telex. :-)
>>> >
>>> > 73
>>> > Henning DF3OE
>>> > i-Telex 925302
>>> >
>>> > www.i-telex.net
>>> > www.telexforum.de
>>> >
>>> >
>>> >
>>> > Am Mo., 5. Sept. 2022 um 22:54 Uhr schrieb Paul Heller <
>>> paul0926 at comcast.net>:
>>> >>
>>> >> Nice machine!
>>> >>
>>> >> A fan is an interesting idea. A small one that runs off 120vac
>>> perhaps.
>>> >>
>>> >> I don’t have that insulator in mine and I think Wayne’s suggestion to
>>> remove it is a good one. I often leave the lid opened to let air circulate
>>> in there.
>>> >>
>>> >> It seems like a bad design. The European machines have a relay which
>>> is much better. I don’t know how they dissipate power from the small amount
>>> of loop current when not in a call, but I’ve not noticed heat build up in
>>> them. Yes it gets pretty warm and I often worry about that but so far all
>>> is doing ok on my machine. I do power it off when going away for any
>>> extended amount of time.
>>> >>
>>> >> Paul
>>> >> W2TTY
>>> >>
>>> >> > On Sep 5, 2022, at 4:37 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>>> >> >
>>> >> > 
>>> >> > Hey folks, I recently got my M32 up and running on i-Telex and all
>>> is good but things are getting a little toasty and I am not sure how much I
>>> need to worry.  Please see attachments - the circles I drew show where it's
>>> getting hot.  120-130F if my Harbor Freight thermometer is to be believed.
>>> >> >
>>> >> > As there is quite a bit of room in there, I was wondering if a
>>> small fan would be helpful.
>>> >> >
>>> >> > Any thoughts appreciated!
>>> >> >
>>> >> > thanks
>>> >> > Andy
>>> >> >
>>> >> >
>>> >> > ______________________________________________________________
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>>> >> >>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
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>>> >> >
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>>> >> >>> Jordan Spencer Cunningham's GreenKeys Search Tool:
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>>> >
>>> > >>> Jordan Spencer Cunningham's GreenKeys Search Tool:
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>>> http://mailman.qth.net/pipermail/greenkeys/
>>> > >>> 1998-to-2001 greenkeys archive:
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>>> >
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>>>
>>> >>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>> https://teletype.net/gksearch
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>>> http://mailman.qth.net/pipermail/greenkeys/
>>> >>> 1998-to-2001 greenkeys archive:
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>>>
>>> This list hosted by: http://www.qsl.net
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>>
>> ______________________________________________________________
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>>
>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>> https://teletype.net/gksearch
>>
>> 2002-to-present greenkeys archive:
>> http://mailman.qth.net/pipermail/greenkeys/
>>
>> 1998-to-2001 greenkeys archive:
>> http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>
>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>> http://comcents.com/tty/greenkeyssearch.html
>>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
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