[GreenKeys] Current loop not providing (enough) current

[Ralph Mowery]

Ok, this points to the PC board doing something wrong.  

 

I don’t have the schematic for that board to help any more at this time.    You should be able to short out or just take the PC board out of the circuit and the teletype should type from the keyboard.   Just remember what I mentioned about the coils could be what I call out of phase and the wires on one may need to be reversed.

 

 

I don’ tknow if a transistor or IC (optical  isolator) is being used to switch the loop off and on.  Whatever it is, is probably bad or whatever driving it is not driving it hard enough to put it into full conduction.

 

I do not do DMR.  Have no plans for it as of now.  I can operate any band from 80 to 10 meters and even higher ,but you are probably too far away.  

 

I am located in the middle of  North Carolina, where are you  ?

 

Ralph ku4pt

 

 

From: Zach Zarzycki [mailto:shardsofaperture at gmail.com] 
Sent: Thursday, September 26, 2019 8:20 PM
To: Ralph Mowery
Cc: GreenKeys
Subject: Re: [GreenKeys] Current loop not providing (enough) current

 

Ok, so the power supply and resistors made 60 ma, when I hook the power supply up to the PC board, drops in half to 30 ma (no teletype on the loop). It was my understanding the polarity into the PC board didn't matter if it was hooked. I'll try to flip them. 

 

But at this point supply to resistor in a loop is 60mA!

 

 

As an aside, the teletype does measure about 45 ohm.

 

 

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