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

Tue Sep 6 11:03:05 EDT 2022

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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>
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