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hexsane
July 1st, 2009, 07:50 PM
My lastest (and probably greatest although I did find an Intel 4004 once) find:

http://vintagemashups.net/pics/imsai8080.jpg
http://vintagemashups.net/pics/insideimsai.jpg
http://vintagemashups.net/pics/s100set1.jpg
http://vintagemashups.net/pics/s100set2.jpg
http://vintagemashups.net/pics/cpu.jpg

What needs to go where?

This is as I found it. I'm not sure if I have a CPU though the last picture is a Z80 with support logic. I'll make a list of the cards when I get a few minutes.

Dwight Elvey
July 1st, 2009, 09:37 PM
Hi
It looks like the Z80 board is a universal IMSAI/ALTAR board. The
8 pin connector on the right top would be used to connect the
front panel of the ALTAR while the 16 pin socket near it would
go to the IMSAI front panel. This would require that it be connect
to the first socket behind the front panel.
The other boards should not have any particular order. I'd check
each one at a time, being ready to turn the power of quickly.
Some recommend connecting things through a 60W light the first time.
Others recommend slowly powering up with a variac. Some recommend
both.
If you can get the main chassis to power up without blowing a fuse
or anything, I recommend plugging each board in one at a time.
Turn the power on for the count of 3 seconds. Then feel all the caps
for any that are hot. If none are hot, increase to 10 seconds and check
again.
Any smoke should indicate removing the power right away.
Once you have the cpu card working on the front panel, you can start
checking out the RAM boards.
Some of the other boards, I'm not sure what they are. I'd need closer
inspection and part numbers of any major parts.
Dwight

hexsane
July 1st, 2009, 10:10 PM
Card List:

Digital Systems Bus Interface HB-1.4
CCS Model 2032 32k Static RAM
Dual Channel RS232 Serial I/O INTERFACER1 CompuPro Godbout
MIO REV 2
Card that looks identical to the MIO but not marked.
BOB MULLEN TB-2 Buss Extender / Prototyping Board.
2x D.R.C. EPROM cards. (1 is missing parts)
S.D. SALES by MICRONIX (z80 CPU card)
3x ECONORAM II 8k Card
PIO REV 2 IMSAI
RAM-4A REV 2
TPS 100B A. SZERLIP 1977 (Attaches to a rotatory switch on the back of the IMSAI with labels for EPROMs (2708, 2716)

A pin is missing from the header that fits on the CPU. I have one in a bin so that will be my first fix.

Dwight Elvey
July 2nd, 2009, 07:17 AM
Hi
The Digital Systems board goes with the disk system
that was one of the first to be used on the S100.
You need the box that has the controller and one or two
SA800 drives.
I have one of these systems. It is cool in that you don't
need a boot ROM. On power up, the disk system will
DMA the boot sector into RAM. All one does then is hit
RUN ( If the disk is CP/M then it is up and running ).
Check out the following for more information:
http://www.retrotechnology.com/dri/microcode.html
Dwight

RichCini
July 2nd, 2009, 08:38 AM
Card List:

Digital Systems Bus Interface HB-1.4
CCS Model 2032 32k Static RAM
Dual Channel RS232 Serial I/O INTERFACER1 CompuPro Godbout
MIO REV 2
Card that looks identical to the MIO but not marked.
BOB MULLEN TB-2 Buss Extender / Prototyping Board.
2x D.R.C. EPROM cards. (1 is missing parts)
S.D. SALES by MICRONIX (z80 CPU card)
3x ECONORAM II 8k Card
PIO REV 2 IMSAI
RAM-4A REV 2
TPS 100B A. SZERLIP 1977 (Attaches to a rotatory switch on the back of the IMSAI with labels for EPROMs (2708, 2716)

A pin is missing from the header that fits on the CPU. I have one in a bin so that will be my first fix.


I noticed the twisted-pair of wires on the right-hand side connecting to the front panel board, but I can't see where it goes. This is the power switch wire and if it's wired "stock", it's connected directly to the power supply board which means it's carrying mains voltage.

IMHO, this is the worst design choice ever because it's mixing line voltage and logic voltage in close proximity *and* it's not shielded. There were two common fixes: First is to disable the front panel switch and use a switch on the back panel to control the power. The second is to convert the switching to low voltage with a relay and put a "master" power switch on the back panel. This at least preserves the use of the front panel power switch but requires a small relay and transformer to power the relay (like 120v-6vac).

My IMSAI came with the first modification but I converted it to the second to preserve the functionality of the front panel power switch. There are probably designs which don't require the use of a second step-down transformer, but I used what I had "in stock".

Dwight Elvey
July 5th, 2009, 10:00 PM
Hi
The Digital Systems board goes with the disk system
that was one of the first to be used on the S100.
You need the box that has the controller and one or two
SA800 drives.
I have one of these systems. It is cool in that you don't
need a boot ROM. On power up, the disk system will
DMA the boot sector into RAM. All one does then is hit
RUN ( If the disk is CP/M then it is up and running ).
Check out the following for more information:
http://www.retrotechnology.com/dri/microcode.html
Dwight

Hi
Somehow I posted this to the wrong group.

http://news.mydrivers.com/pages/images/20051109184445_28157.jpg

The Digital Systems drive is on the bottom of the stack.
Most were blue to match the IMSAI but some were a light brown
as well. You need to keep an eye out for these to get something
to match the interface card.
Dwight

hexsane
July 5th, 2009, 10:42 PM
I went back to where I found the IMSAI and did another search but didn't find anything. Unfortunately this is a recycling place and that drive system probably ended up being chewed up or shipped to a processor. :(

I'm finishing a few projects around here before diving into the IMSAI hopefully I'll get to it later this week.

-Matt

Dwight Elvey
July 6th, 2009, 06:47 AM
I went back to where I found the IMSAI and did another search but didn't find anything. Unfortunately this is a recycling place and that drive system probably ended up being chewed up or shipped to a processor. :(

I'm finishing a few projects around here before diving into the IMSAI hopefully I'll get to it later this week.

-Matt

Hi
I'd recommend hanging on the the interface card but get another
floppy card that has the controller on the board. You'll need a
ROM card to run it but it looks like you have one of those.
Just keep an eye out for the Digital Systems drives. They
show up every now and then without the interface card.
Dwight