IMC-2001
IMC-2001
This is an old Taiwanese Apple ][ / CP/M clone.
Status
Trying to fix several issues:
- power switch makes some hissing noises
- the lever moving the contacts between 40-character and 80-character mode for the CRT output is corroded, doesn’t always make contact and produces a flickering image
- keyboard cable is broken, at least the data line
- the paddle and the joystick connectors miss some legs for putting them into the sockets on the motherboard
- sometimes I get into the monitor
lower-nibble bit 3 of the key being pressed is missing, unclear where it is lost, I suspect a bad register on the motherboard holding the current ASCII value of the key pressed or something similar. Replaced a bad 74LS257N, works now just fine.- ROM 1 with BASIC is broken (and gets really hot). This explains the booting issues.. (will be tricky to get a replacement)
- possibly much more
Known things to work
- The keyboard works electronically (8039 MCS-48 like CPU with a 2K EPROM)
- the Rockwell R6502 CPU has a phase 0 clock and seems to go through address lines and output data (another strong indicator is the ‘Apple ][’ sign on the monitor when switching on which indicates 6502, 40-character ROM, video circuit seems to be just fine).
- Monitor is working just fine (which is sort of amazing for such an old CRT monitor).
- I can boot from a Apple ][ CP/M 56k floppy and I get a prompt, now as the keyboard works and the CP/M on the 80-character card I can also assume the Z80 is working just fine.
Images
From the outside:

Booting into Apple ][ CP/M 56k:

The motherboard and floppy drives:

Keyboard layout:

Keyboard has a 8039 CPU inside and a 2K EPROM:

On the oscilloscope:

Broken keyboard cable (the black pins are just connectors added by me to test connectivity, both connector are female per default):

Documentation
This is the “Operation Manual for IMC-2001, version 2.01”:

Schematics
Power connector on the motherboard:
O O O O O O
| | | | | +--- GND black
| | | | +----- +12V red
| | | +------- -5V blue
| | +--------- -12V brown
| +----------- +5V white
+------------- +5V white
keyboard cable connectors:
connector to machine (sort of a gummy version of a DB-9):
computer has a 9-pin DSUB connector male:
+----------- white INTR
| +--------- black GND
| | +------- green DATA
| | | +----- blue RESET
| | | | +--- Yellow CLOCK
-------------
\ O O O O O /
\ O O O O /
---------
| | | +---- red 5V
| | +------ n.c.
| +-------- n.c.
+---------- n.c.
On the keyboard PCB there is a strange white connector with the following layout:
+------------- white INTR (active low, after last clock tick)
| +----------- black GND
| | +--------- blue RESET (active low)
| | | +------- green DATA
| | | | +----- yellow CLOCK
| | | | | +--- red +5V
+-----------+
|o o o o o o|
+-----------+
| |
Links
- Mention of the IMC-2001: mentions it on the list of Apple clones
- Youtube video of similar machine: “APPLE II CLONE + CP/M ——- IMC 2001 made in taiwan.——–”, Retro Computacion Argentina Jorge E. Nuviola