Another source of transformers is industrial control transformers. Many have two primaries for 120/240 volts in. If you find one that is 50 VA, the two primaries can be connected one to the line and the other to the load and used as an isolation transformer for a loop circuit.  A model 19 needs a  good bit of  current for the punch, a 250 VA transformer would be plenty for both the punch and the loop. Look around for them on the internet and at hamfests, used ones are often inexpensive.

     Brenda Gentry, KA2IVY

They sell 120v 1:1 isolation transformers for arcade machines. That and a bridge gets you 120vdc. Theyre not even all that expensive (ok they werent last time I looked lol)

Jeff

On Mar 2, 2026, at 8:06 PM, W2HX <[email protected]> wrote:



Why not two of these back to back (12VAC to 12VAC)? One less xformer

https://a.co/d/0heT4Zus

 

then rectify.

 

73 Eugene W2HX/4
My Youtube Channel: https://www.youtube.com/@w2hx/videos

 

 

From: [email protected] <[email protected]> On Behalf Of Johannes Eggers
Sent: Monday, March 2, 2026 7:10 PM
To: [email protected]
Subject: [GreenKeys] Model 15/19 power supply 120VDC

 

I'm building a 120VDC power supply for my frankensteined Model 15 / 19.  The plan is to take 3 transformers with 28V secondaries in series, gets me 84VAC, then a rectifier and maybe smoothing capacitor.  I'm not sure about the VA rating for the transformers.  I calculated 7.2VA for the current loop (60mA * 120V DC), but I'm not sure about the perforator.  Anyone have numbers for that?  Also, am I missing something?

 

Thanks !

 

Johannes

 

 

______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]

Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch

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
Message delivered to [email protected]

______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]

Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
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
Message delivered to [email protected]