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+++
title = "IMC-2001"
+++
# IMC-2001
This is an old Taiwanese Apple \]\[ / CP/M clone.
# Status
Trying to fix several issues:
- the floppy drives read floppies (both) but they don't write to floppies
(when copying in CP/M or creating a file), they work when formatting
a drive on CP/M though. ~~Could be a side-effect of the PSU not working properly.~~
The PSU has been replaced, the voltages look ok, so I rule out the PSU.
Could be some missing code in the Apple ROM (but that would be weird to
call 6502 firmware code from the Z80 CPU). It could also be the write
current being to low for writting (but why does formatting a drive work then?!)
- 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
- the CRT is producing some flickering when turning the brightness nob,
this should be fixable with some deoxit.
- there could be grounding/signal issues causing the flickering of the CRT
(stemming from the replacement PSU).
- 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
- possibly much more
- the keyboard reset line cannot be taken to ground on the keyboard, works
with shrtening ground and reset though just fine. Must be a bug on the
ICs of the keyboard controller or a broken trace.
Fixed issues:
- ~~ROM 1 with BASIC is broken (and gets really hot). This explains
the booting issues.. (will be tricky to get a replacement). The
board layout doesn't fit to the original ROM sizes too..~~
Got an AT28C256, no more frying of chips, Apple Basic prompt appears,
tested some commands and it seems fine. The 32k ROM has to be filled in
starting from 0x6000 with #E000-$EFFF and from $7000 with $D000-$DFFF.
If this ROM is ok we will see.
- Reseated and deoxied all ICs, some of them were quite corroded, at
least 3 more turned out to be bad. Sadly it didn't have an effect on
ROM 1 not getting hot (must be something else).
- ~~power switch made some hissing noises, it was not the switch, now
the original power is dead (and some transformers are humming). Ordered
a Apple 2 replacement PSU, waiting for it..~~
The new replacement power supply works like a charm, also replaced
the power switch, the old one was too unreliable.
- ~~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.
Not fixed issues:
- ~~The 220V fan no longer works.~~
I just disconected it, I don't think, it really helps to cool the system.
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 \]\['
sign on the monitor when switching on which indicates 6502, 40-character
ROM, video circuit seems to be just fine).
- Monitor is working just fine (which is sort of amazing for such an old
CRT monitor).
- I can boot from a Apple \]\[ CP/M 56k floppy and I get a prompt, now
as the keyboard works and the CP/M on the 80-character card I can also
assume the Z80 is working just fine.
- the 80-columns card (a Videx Videoterm or rather a clone of it) works just fine.
- the highres graphic mode works just fine, I can run "Peter Anvin Chess" and play it.
# Images
From the outside:
{{< figure src="/images/hardware/imc-2001/computer_full.jpg" alt="IMC-2001" >}}
Booting into Apple \]\[ CP/M 56k:
{{< figure src="/images/hardware/imc-2001/cpm_40chars.jpg" alt="IMC-2001" >}}
The motherboard and floppy drives:
{{< figure src="/images/hardware/imc-2001/motherboard_internal.jpg" alt="IMC-2001" >}}
Keyboard layout:
{{< figure src="/images/hardware/imc-2001/keyboard_front.jpg" alt="keyboard layout" >}}
Keyboard has a 8039 CPU inside and a 2K EPROM:
{{< figure src="/images/hardware/imc-2001/keyboard_pcb_controller_prom.jpg" alt="PCB and controller" >}}
On the oscilloscope:
{{< figure src="/images/hardware/imc-2001/oscilloscope_serial_keyboard.jpg" alt="serial keyboard signal" >}}
Broken keyboard cable (the black pins are just connectors added by me to test connectivity,
both connector are female per default):
{{< figure src="/images/hardware/imc-2001/keyboard_cable.jpg" alt="PCB and controller" >}}
Old PSU:
{{< figure src="/images/hardware/imc-2001/old_psu.jpg" alt="New PSU" >}}
New PSU replacing the old crusty one (this is a standard replacement PSU for
Apple \]\[ from [Reactive Micro](https://wiki.reactivemicro.com/Universal_PSU_Kit)):
{{< figure src="/images/hardware/imc-2001/new_psu.jpg" alt="New PSU" >}}
# Documentation
This is the "Operation Manual for IMC-2001, version 2.01":
{{< figure src="/images/hardware/imc-2001/manual_frontpage.jpg" alt="manual frontpage" >}}
[The complete scanned manual](/hardware/imc-2001/manual_imc_2001_2.01.pdf)
(also on archive.org, see [https://archive.org/details/manual_imc_2001_2.01](https://archive.org/details/manual_imc_2001_2.01))
# Super Serial Card
I got a super serial card from Ebay, the documentation of it can be
found here [https://archive.org/details/Apple_II_Super_Serial_Card_1981_Apple](https://archive.org/details/Apple_II_Super_Serial_Card_1981_Apple).
# 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](http://www.epocalc.net/php/liste_models.php?texte=&look=All+fields&yearmax=2018&nocomp=pc&cat=Apple+2+clone):
mentions it on the list of Apple clones
* [Youtube video of similar machine](https://www.youtube.com/watch?v=c7crlJg80Zg):
"APPLE II CLONE + CP/M ------- IMC 2001 made in taiwan.--------", Retro Computacion Argentina Jorge E. Nuviola
|
