[GreenKeys] RS232-Current loop converter troubleshooting

[Sarah Autumn]

So the power supply I'm using right now is a Teletype REC-50. Voltage
measured directly from the supply is 135VDC, and at the resistor is 130VDC.
Pretty sure we're good in that area...unless I"m missing something.

I have a *bunch* of other power supplies lying around, including something
like the one you mentioned, transformer, rectifier, capacitor, from a Model
28 ESU. Let's try that.

On Tue, Jan 19, 2016 at 8:53 AM, drlegendre . <drlegendre at gmail.com> wrote:

> 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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