[GreenKeys] inexpensive loop supply transformer wanted

[Jack Hart]

Ken,

Thanks for the info. I just ordered two of them.
The "110VAC secondary" transformers produce a little too
much DC with a cap and bridge diode, although the TTY's
would handle it.

73,
Jack K0TTY

NNNN



-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Ken Schwieker
Sent: Saturday, December 21, 2013 5:49 PM
To: GreenKeys at mailman.qth.net
Subject: Re: [GreenKeys] inexpensive loop supply transformer wanted

If you don't want the approx 160+ volt loop supply with some of the problems
associated with that high of a supply there are inexpensive lower voltage
transformers available.

Here is the info I posted about this particular transformer some time ago.
These transformers look to be well made and most likely in US.

Just a heads up on a source of very reasonably priced transformers suitable
for loop supplies.
Can be used to construct a supply with a somewhat lower and safer voltage
than the usual 140 volt or higher ones.
Did some tests, primary at 120 v;
74 v ac no load
70 v ac with 100 ohm load (700 ma)
One hour with 100 ohm load connecter, transformer temp 110 F (ambient about
70 F).
Size,  3" x 2 1/2" x 2 1/2" high not counting chassis mounting tabs. 
Mounting holes 3 1/2" between centers.
Only two terminals on the bottom (pri) and three on the top (center tapped
secondary) are used.
I purchased 3 and the total was around $25 including shipping

http://www.apexelectronic.com/TR5-W-26

Ken S

 >At 11:56 AM 12/20/2013, you wrote:
I'm working on a small project to have a Single Board Computer such as a
Raspberry Pi or Arduino drive my TTYs (Model 15 at 45 WPM and a
28 RO at 75 WPM) with some canned messages from memory.  As part of that
effort I'd it to have it's own loop supply (120VAC to 120VAC isolation
transformer, bridge rectifier, filter cap, 2800 ohm 20 watt limiting
resistor).  Does anyone have suggestions on where I might find a low cost
isolation transformer for this purpose?

 >Paul Newland, ad7i

______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:GreenKeys at mailman.qth.net

2002-to-present greenkeys archive:
http://mailman.qth.net/pipermail/greenkeys/
1998-to-2001 greenkeys archive:
http://mailman.qth.net/archive/greenkeys/greenkeys.html
Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
http://comcents.com/tty/greenkeyssearch.html

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html