Req: Help/Advice on Cromemco System

[Dave McGuire]

On Oct 17, 2008, at 10:15 AM, Granz wrote:
> I have most of the stuff to put together a System 3.  I have the  
> card cage with the 21-slot motherboard and a bunch of cards.  The  
> manuals I got with the system include the Cromix manual, I have  
> more than 1 64-K RAM card and at least one TPU, so I believe that  
> mine was a multi-user system.  I would like to put this back to  
> near-original, but need a case and power supply.
>
> Since I have been unable to find any power supplies which provide  
> the +/- 8 and +/- 16 volts, I just thought of an idea the other day  
> of using a PC power supply and shorting out the on-board voltage  
> regulators to allow them to work at the +5V and +12V of the power  
> supply.  In order to do that though, I would need a small (3-5  
> slot) motherboard to test a couple of cards together.

   I don't think it's going to be possible to short around the +5 and  
+12 regulators in a PC power supply, as they're not discrete in that  
way.  Your best bet (IMO) is to surf eBay for an big open-frame  
linear power supply.  These are usually based on LM723 voltage  
regulators and 2N3055 (or similar) pass transistors, and it's easy to  
bridge around that sort of regulator.  Otherwise you can just tweak  
the voltage upward to the 8/16 that you want using the adjustment  
variable resistor that's usually present in such power supplies.

> If anyone has any of these available, I would be interested in  
> obtaining them.

   Sadly I do not, but...

>   I do not have much money, but do have some other old computer  
> stuff that I can trade: a VAX Station 2000, an old Sun workstation,  
> many, many old PC parts and systems, lots of electronic parts,

   What model of Sun?

> lots of microcontroller stuff including several Dev Kits.

   I'm definitely interested in that stuff, if I have anything else  
you may be looking for.  What sort of microcontrollers and dev kits?

             -Dave

-- 
Dave McGuire
Port Charlotte, FL