[GreenKeys] RS232-Current loop converter troubleshooting

[drlegendre .]

In case this isn't totally clear, the Aetherics design +must+ be supplied
from a 120V DC supply that +lacks+ a current-limiting series resistor. A
simple linear supply (xfmr + rectifier + cap) is all that is required. The
2K 10W part inside the converter handles all of the necessary current
limiting for you.

If you try to power it with a current-limited supply, chances are the
current would be too low to operate the selector magnet in the M15.

On Mon, Jan 18, 2016 at 7:02 PM, Sarah Autumn <neverether at gmail.com> wrote:

> I tried 2 different supplies. One was an acoustical coupler modem, which
> does have its own resistor, and I also tried a Teletype REC-50 which I
> believe does not have its own. Not sure though. Could open it up and check.
> On Mon, Jan 18, 2016 at 4:01 PM <hwhall at compuserve.com> wrote:
>
>> That sounds suspiciously like a problem I've seen one or two times. A
>> wire or contact is broken or in poor contact, a high resistance contact, so
>> that it can carry a very small current (milli or micro amps) and show near
>> normal voltage but when more current is demanded, the voltage drop becomes
>> large and the load isn't satisfied. Worst case was broken wire inside an
>> otherwise OK-looking length of zipcord. Took a while to actually believe
>> what the meter was telling me because I "couldn't see anything wrong."
>>
>> Check all the wires, connectors and related solder joints closely for
>> minute breaks, cold joint, etc.
>>
>> Wayne
>> WB4OGM
>>
>> -----Original Message-----
>> From: Sarah Autumn <neverether at gmail.com>
>> To: Greenkeys <greenkeys at mailman.qth.net>
>> Sent: Sun, Jan 17, 2016 10:17 pm
>> Subject: [GreenKeys] RS232-Current loop converter troubleshooting
>>
>> Hi all,
>>
>> I finally got around to building the loop to serial converter that
>> everyone knows and loves (http://www.aetherltd.com/connecting.html). It
>> worked fine at first, but now I'm getting this weird behavior.
>>
>> When there is no teletype connected, on the pins for the selector magnet
>> (J1 5&6) have voltage. When I connect the teletype to the pins, the voltage
>> drops to almost nothing, and the magnet doesn't operate. If I remove the
>> teletype from pins 5&6, the voltage jumps back up to 100V. When I hook the
>> teletype directly to my loop supply, it runs fine.
>>
>> I have also tried 2 different power supplies: One is an acoustic coupler
>> modem used for the deaf, and another is a REC-50.
>>
>> I have checked the values of all my resistors and capacitors. What
>> simple, easy thing am I doing wrong?
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>
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