[GreenKeys] loop supply

[Harold Hallikainen]

It looks to me like the two selenium rectifiers are forming a full wave
rectifier driving an electrolytic capacitor. The red wire from the
electrolytic is the positive end of the supply,and the black wire is the
negative end. These then both end up on the barrier strip. The red wire
goes to the parallel power current limit resistors. So, the loop output
would be from the end of the resistors not connected to the red wire, and
the black wire. The black wire would be the negative end of the current
loop supply, and the resistor end would be the positive end of the current
loop supply. Ideally you could put a milliamp meter between these two
points and see close to 60 mA.

I notice also that the green wire of the line cord is not connected to the
chassis as it should be.

Harold
https://w6iwi.org


On Thu, May 18, 2023 2:12 pm, Virgil Bierschwale wrote:
> A few years ago somebody sent me this loop supply to get my model 28 KSR
> running.
> Sadly, I guess my electronics skills are no longer good as I'm not sure
> how
> to hook it up.
>
> In case the picture doesn't come through, it has a teletype 152950 120 ma
> loop supply attached to a box that has a switch and terminal strip in it.
>
> The red and black wires from this supply go to:
> red to two large resistors in parallel
> black to the terminal strip.
>
> I'm thinking I need to take the output of the resistors and run it to the
> teletype and then take the output from the teletype and hook it to the
> black wire on the terminal strip which will complete the loop.
>
> Is that correct?
>
> Thanks,
>
> Virgil
> N5IVV
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