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RE: [N8VEM-S100:6333] Re: New S-100 Computer - first test photos

Well, yes, but not so much a trick, as just getting somewhere close to the minimum load on the supplies that require it.  Ordinarily, they would not be needed.  But since I want to use this for testing, I want to be sure the PSU turns on properly with an unpredictable or very light load.


I have added a 8” floppy drive and am working on getting the boards populated into the buss.  I’ll post more photos after I have it running.


Bob Bell



From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Todd Miller
Sent: Monday, February 16, 2015 5:10 PM
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:6333] Re: New S-100 Computer - first test photos


Very Cool !  

Are you using the large load resistors to 'trick' the PSU ?

I've done this to PC supplies to run without the motherboard.

On Sunday, February 15, 2015 at 4:21:02 PM UTC-6, Bob Bell wrote:

I have completed the base, backplane and power supply portions of my new S-100 computer.  This will be used for testing purposes, so was designed to be open and accessible, and I built it on a wooden base.  The backplane is the N8VEM version 2, slightly modified, and the power supply is a MeanWell QP-200F.

The MeanWell ps outputs 5V, so I modify and run all my S-100 boards without the 5V regulator.  Hence, the backplane was modified by not installing the regulator; I just jumpered the input to the output.  I discovered that the orientation of Q1 was incorrect, so that transistor has to be installed backwards from what the silkscreen shows.  And I could not find resistor arrays with leads long enough to protrude through this overly thick PCB enough to solder.  So, I made my own arrays out of discreet resistors and some spare protoboard PCB material from another project.  As for the power connector, I utilized a Phoenix Contact screw-terminal connector.  Finally, since the fuses only protect the LEDs, I eliminated those.

The large unoccupied area of the base board is drilled and ready to mount up to 2 full-sized 8" floppy disk drives.

Photos of this new computer are attached (I hope!)

Bob Bell

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