[GreenKeys] 255A Polar Relay correction

[John, W9DDD]

Your solution to getting a Dovetron connected into your local loop 
interests me.

I'm interested in driving a polar relay from a low voltage output 
(perhaps RS232?).  From what I can see from the Dovetron schematic, it 
drives the FSK output from an op amp which has supply rails of +/- 15 
VDC.  It's called a +- 6 volt output.  It has a 1k current limiting 
resistor.  So I calculate about  5 to 11 mA current to the polar relay 
depending on whether the output op amp is switching from rail to rail or 
is actually limited to +/- 6 volt swing.  My op amp theory is a bit 
rusty, but it looked like it would do the rail to rail from looking at 
the schematic.

My take away is that the 255 will switch with a lot less than 20 or 60 
mil line current.  Does that sound reasonable?

I'm thinking there needs to be an RC snubber in the circuit to protect 
the solid state driver from "inductive kick".

---
----
You said "tomorrow" yesterday.

The above comments or recommendations are SWAG. Use at your own risk.
John, W9DDD

On 1/16/2023 11:09 AM, Tom Hunter wrote:
> Pins 3 and 7 are jumpered to put the windings in series aiding by 
> bending the tube socket pins and tack soldering them together.
>
> Tom   N3CRK
>
>
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