[GreenKeys] Use of Volpe Board

[epvgk at limpoc.com]

On Fri, Sep 06, 2019 at 08:43:40PM -0500, E. wrote:
> 
> What kind of a heatsink would you recommend for those big, honking, through-hole resistors ;o ???
> 

They don't actually need one, but I wouldn't put it inside a closed plastic box or
anything subject to heat damage.  The old Model 19 tables I think just have them 
screwed to the body of the table. Mine just sits in the open inside my model 28 
tabletop chassis and keeps it from getting too cold at night. :) 

eric


> 
> > On Sep 6, 2019, at 8:28 pm, epvgk at limpoc.com wrote:
> > 
> > For people who are considering using this board to interface a TTY loop with a computer, and
> > who don't already have an existing current loop, here is what I'm using. 
> > 
> > This power brick is kind of overkill but not too expensive, and more importantly to me at least
> > is very RF-quiet, so if you do radio stuff too it doesn't produce much RFI at all. 
> > 
> > https://www.aliexpress.com/item/33039935845.html
> > 
> > You also need to limit loop current to (ideally) 60 mA for 14/15/28/etc type machines, so put
> > it in series with a 20+ watt 2K resistor like 
> > https://www.parts-express.com/2k-ohm-20w-resistor-wire-wound--017-2k
> > (it will get hot, give it a heat sink or space to breathe!)
> > 
> > For 20mA machines you could use the same resistor but a 48VDC supply and probably be ok, if 
> > the teletype doesn't already provide loop current. 
> > 
> > eric