[GreenKeys] GreenKeys Digest, Vol 107, Issue 14

Sat Dec 8 20:26:44 EST 2012

Gil,

Changing from 20 MA to 60 MA is quite easy. 

The first change is on the large green resistor just behind the LOCAL/OFF/LINE switch.  A resistor with 4 slide on taps.  Looking from the front of the TTY, 20 MA has the left connection on the outside of the resistor.  60 MA the outside left is empty and the wire is on the next tap in.  

The second option is on the terminal strip.  20 MA has the purple wire on 9, 60 MA has the purple wire on 8.  

60 MA is normally used with half duplex and 20 MA is commonly used with full duplex.  

73,

Wayne

-----Original Message-----
From: gil <gil at baudot.net>
To: nagle <nagle at animats.com>; greenkeys <greenkeys at mailman.qth.net>
Sent: Sat, Dec 8, 2012 5:43 pm
Subject: Re: [GreenKeys] GreenKeys Digest, Vol 107, Issue 14

Yeah, and the 33 is quite happy with a nice, safe low voltage loop of even 20 or so volts. Note that the loop supply is listed as a DC voltage (not AC).  The loop supply, as John pointed out, is a MAX dc voltage on the loop circuitry, but they are often lower voltage loops, dependent on the loop supply/keyer to which you hook the 33.

It's the motor and power-supply input that is the high-power AC input.  The AC input NEEDS to be 115 AC.   Well, yeah 110 to 120-ish.

I have not looked lately but I recall that there is a jumper in the 33 somewhere for 60- or 20mA dc loop -- mine is set to 20, which an even lower-power loop circuit.

Wayne?  Jack?  You guys know all this good M33 stuff.

gil smith
greenkeys moderator
gil at baudot.net
www.baudot.net
Vaux Electronics: 480-354-5556

-------- Original Message --------
Subject: Re: [GreenKeys] GreenKeys Digest, Vol 107, Issue 14
From: John Nagle <nagle at animats.com>
Date: Sat, December 08, 2012 2:49 pm
To: greenkeys at mailman.qth.net

On 12/8/2012 1:09 PM, greenkeys-request at mailman.qth.net wrote:
> Message: 4
> Date: Sat, 8 Dec 2012 20:56:31 -0000
> From: "Rob Jarratt" <robert.jarratt at ntlworld.com>
> To: <r.jarratt at computer.org>, <greenkeys at mailman.qth.net>
> Subject: Re: [GreenKeys] Powering an ASR 33 Teletype in the UK
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="us-ascii"
> 
> I just noticed something else which is puzzling me a bit. On the ASR 33's
> plate it says:
> 
> 
> 
> Supply Input: 115V 50Hz AC 5Amp Max
> 
> Signal Input: 120V.D.C MAX 0.07Amp Max
> 
> 
> 
> What is the difference between supply input and signal input? I am assuming
> it needs me to provide a 115V 50Hz supply but I am not completely sure now.

The data signal input is a 60mA current loop. The data plate says
the upper safe limits are 120VDC and 70mA.

John Nagle

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