[GreenKeys] RS232-Current loop converter troubleshooting

[Sarah Autumn]

Tried the power supply from the 28. Same thing. Resistor gets plenty hot.
130v when disconnected, machine runs open when connected. Connect the 15 to
my known working supply and it runs fine.

I'm willing to rule out the power supply at this point, as I'm confident
the one I am most recently using does not have a current limiting resistor.

On Tue, Jan 19, 2016 at 7:39 PM, Sarah Autumn <neverether at gmail.com> wrote:

> 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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>>
>>
>
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