[GreenKeys] Teletype Model 15 power Q's...

[Ralph Mowery]

Have you tried running a 15 on the low voltages like 12 or 24 volts ?  The one I have will give all kinds of errors at that voltage.  Seems that around 50 or more volts is where it seems to print without errors.

 

 

From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of drlegendre .
Sent: Tuesday, November 08, 2016 10:59 PM
To: Ed Sharpe
Cc: Green Keys
Subject: Re: [GreenKeys] Teletype Model 15 power Q's...

 

"yes  this is called a loop supply  normally  660 mils at  120 volts  but   for  local loop  less can be used"

I know this was a typo, but I do feel the need to correct it, as the OP is a newb to this stuff.

The standard data loop for older TTYs (M15 included) is 60mA @ 120V DC. This is most easily accomplished with a ~100mA 120V DC supply, in series with a 2K 20W resistor. But this is the loop supply for +long+ loops - as in, cross-town or even cross-country. You can xmit TTY data for several miles on a 120V / 60mA loop. 

For local use, 12-24V DC, limited to 60mA will do the trick. So at 12V use 200R 2W, for 24V use 400R 3W.

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20161108/1bdcc6ac/attachment.html>