MARCH’s Altair 8800

MARCH’s Altair is S/N 220072: a kit delivered around Jan 1975.
These photos are to chronicle all options and the condition.
On 15-September-2011, I prepared the Altair for the NYC Maker fair
  1. removed a loose bolt from under the backplane
  2. replaced all 4 rubber feet (one was mismatched and cracked)
  3. replaced a missing nut from the backplane corner mount,
    but the entire cage twists enough for cards to pop out while moving it
  4. cleaned out dust from under the backplane
  1. A15 led does not light
  2. One of the card rails is missing
  3. The +8 supply is high, will cause all regulators to run hot

measured voltages

-V +8 +V
no cards -17.1 10.8 17.06
with 2 cards -16.3 10.3 16.2

I need to know: each card's address and details
particularly the ROM's entry points

Inside the Altair 8800

The front panel
Top view
CPU card is on the far left with large white Molex front panel connector
bus termination resistors are soldered directly to the backplane’s right
The front panel is wired directly to the S100 bus
via the white wires along the front panel and to the backplane’s left.
looking underneath:
backplane is Processor Technology, Corp MB-1
ground plane across the rear, to pins 50, 100
front cross buss is -V
center cross bus is +8
3rd cross bus is +V

front panel +5 voltage regulator is underneath the backplane, bolted to the frame

Oblique views of bare frame
MITS 8800 CPU board, rev 0
CPU is intel C8080A
DRAM card
© 1977 by Processor Technology Corp, Assy No 203000
rear says 604514 REV F
32K EPROM II Copyright 1982
Tanner Computers
but it is populated with 16: TMM2016P-2 (2k x 8 static RAM)
ROM card
top silkscreen: © 1977 by Processor Technology Corp Assy No 210000
rear says PC210001 rev C
Graphic card
top: © 1976 Processor Technology Co
rear: Processor Technology Co VDM © 1976 rev C
Processor Technology Co 3P+S I/O (serial, parallel I/O)
connects to DB25 on rear panel via top connector
AMI S1883 UART is the large chip

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