Motherboard Status

[Rich Leary <richar...@gmail.com>]

Just a quick update. While I have been wworking with Andrew and John
on the 6502 CPU board design I have also been working on my 28 (?)
year old S-100 cabinet. The cabinet was a Vector product and overall a
nice cabinet. I use basically the same cabinet for the dual eight inch
floppy cabinet. Back panel for the S-100 cabinet has connector punch
outs (DB25, Centronics) that the back panel on the floppy cabinet does
not have.

I pulled the old, homebuilt linear supply out and also pulled the old
and somewhat worn Vector Graphix 18-slot mother board. The motherboard
had some bad pins in some connecctors and even with the CompuPro
terminator board I used it was a little flaky.

The 6-slot N8VEM motherboard was installed in the chassis and the
usual lenghty process of getting the motherboard support rails, the
motherboard, and the card guides aligned went well if slowly. I may
redo that alignment as it is a little on the tight side but it is OK.

I stripped the power supply chassis of all components (very heavy
transformer, multiple large electrolytic caps, multiple rectifiers,
wiring harness, etc.), cleaned the chassis up, and mounted the three
MeanWell switchers on the chassis. I then re-built the chassis wiring
harnesses (AC plus a feed from the +15V DC supply to power the front
panel power indicator lamps), the back panel wiring harness (AC only),
and the front panel wiring harnesses. I already had the wiring harness
that connects the supplies to the motherboard as that had been used
for the out-of-cabnet testing.

I saved the major components from the linear supply as many of those
are also used in the eight inch floppy power supply. The floppy power
supply is more complex as the 24V, 5V, and -5V supplies are all
regulated but it is nice to have some spares. Funny thing is I am now
thinking about converting the floppy power supply to switchers
also. ;-)

The difference in weight with the switchers versus the old linear
supply is amazing.

I ran several tests along the way to verify the wiring (I get very
careful when wiring 115V AC!!!) including AC tests with nothing
connected to the switcher outputs. All went well and when it came time
for the all-up test everything worked well.

I'll try to get some photos of the inside of the cabinet.

So now my S-100 system is running just fine with the cooling blowers
humming along. Something very comforting about real muffin fans!

At some point I may upgrade to the eight-slot motherboard but the six
slot actually is probably enough. I have five slots occupied (CPU,
RAM, FDC, MFM controller adapter, serial/Centronics I/O) and am
thiking about adding a PIC/RTC board in the open slot.

Once I get the IDE board and build it up and integrate it with both CP/
M and DOS/65 the MFM controller adapter will probably be deactivated
and the IDE (CF card) will become the hard disk in the system. That
will eliminate the external MFM controller & drive cabinet as well.
The MFM drve (CMI 5619) is probably on borrowed time and buying a new
(used) MFM drive is possible but tends to be expensive for the
capacity you actually get. (I have the same worry for my Kaypro 10!)

I may also move towards eliminating the eight inch drives and either
boot directly to the hard drive (IDE) or one of the other floppy
drives (most likely the Kaypro 4 drive).

We'll see...

Rich