[GreenKeys] Model 15/19 power supply 120VDC

[Brenda Gentry]

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

On 3/2/26 8:29 PM, Jeffrey Golas wrote:
> 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 <w2hx at w2hx.com> 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:*greenkeys-bounces at mailman.qth.net 
>> <greenkeys-bounces at mailman.qth.net> *On Behalf Of *Johannes Eggers
>> *Sent:* Monday, March 2, 2026 7:10 PM
>> *To:* greenkeys at mailman.qth.net
>> *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
>>
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