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

Tue Sep 6 06:55:50 EDT 2022

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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