S-100 power supply transformer - test-drb@ccmp.vtda.org

17 May 2009

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Subject: S-100 power supply transformer
   From: "Andrew Lynch" <lynchaj at yahoo.com>
   Date: Sun, 17 May 2009 16:51:44 -0400
     To: <cctalk at classiccmp.org>

Hi!  Does anyone know of an available transformer suitable for making an
S-100 power supply?  I need 120VAC input and 10VAC output and +/- 18VAC
outputs.

The best I solution I can find is two separate 80VA transformers; one
parallel 10VAC output and another 36VCT output which can be configured for
+/-18VAC outputs. 
Try closer to 8V RMS rectified that will be more depending on load.
Same to the other two. Look up the calulations and see.  FYI you also 
talking for the 8V line 60,000 to 150,000microfarads (at 15-25V) and 
the other two more like 10,000 to 20,000 (at 30V min) microfarad 
capacitors..

Also consider a 240 primary to 16V which on 120 will do 8V then.

However common (standard) voltages are 6.3, 12.6, 25.4 and 48 then there 
are control transformers like 10V, 18V and 24 and sometimes 36.

...
 I would prefer a single transformer rather than dual
transformers because
they are the most expensive part of a linear power supply. 
You will have better luck with two but you may get lucky. FYI the early 
Altair used two.

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I know Northstar and Vector Graphic used similar dual output transformers
but I cannot find anything like them after searching the usual vendors like
Digikey, Mouser, Jameco, etc.  Even transformer manufacturers don't seem to
carry a stock product of this configuration although you can order custom
units. 
Thos are honking big and intended for the then loaded bus of more that a 
few cards.  We talking a +8V good for 25-35A.  More practical systems 
especially those osing newer 64K (on one card) memories tended to require 
far less power.

Try digikey and mouser.

In this day and age those are not common and during the golden age of S100
they were still a bit oddball and not cheap.

Allison

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Thanks in advance for any help.  Your ideas greatly appreciated.  

Thanks and have a nice day!

Andrew Lynch 