[GreenKeys] TTY-Connect pictures and 160V vs 80V info

[gil smith]

Hi folks:

Some of you wanted to see pictures of TTY-Connect, so I put some up:

http://www.vauxelectronics.com/gil/tty-connect/

Also, the high-voltage loops may be configured for either 80VDC or 
160VDC.  To use 80VDC, the transformer primaries are wired in series, and 
to use 160VDC, the transformer primaries are wired in parallel.  The power 
resistor values change too, of course.

I really recommend the 80VDC option, since things run much cooler.  With 
the heatsinks listed in the parts list, the unit set to full duplex (which 
burns additional power), and the loop set for 60-mA, temperatures read:

config       xfrm           heatsink
-------------------------------------------------------------------------
80VDC     100 degrees      125 degrees
160VDC    110 degrees        175 degrees

175 degrees (F) is just too darned hot, in my opinion.  If you really must 
use a 160V loop, it should have a larger heatsink and/or fan.  If you use 
80V, the heatsink listed in the parts list should be fine with vertical 
mounting and simple convection cooling.

Or, if you configure the loop (and your machines) for 20-mA, the 160V 
configuration will run much cooler.  But most folks have 60-mA machines, so 
I still recommend 80V.  I really doubt that anyone will notice the 
slight-to-none reduction in selector range margin.

thanks,

gil


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