My "Apple ][" "Europlus"

My father bought us an "Apple ][", somewhere around 1980. A friend of his was involved with importing Apple clones from Taiwan.

It's a Taiwanese UNITRON, not to be confused with the Brazilian Unitron.

We started off without floppy drives -- I wrote a "breakout" lookalike in Integer Basic, which I eventually lost when the cassette I was using failed.

Later we got floppies, as well as a Z80 softcard and 80 column card for running CP/M.

I spent many many hours on this machine, coding, playing games, hacking games to give more lives, trying to break copy protected disks, and the like. Remember Zardax? It was an "upcopyable" word processor, apparently quite good by 1984 standards. I made the best copy I could, then spent hours trying to figure out why it didn't boot. Never managed to make it work, though...

I managed to scrounge a ROM card, a complete set of Apple ROMs, and a pukka Apple motherboard (unpopulated). I used the ROM card to crack games, both copy protection and nifty things like getting extra lives and axes in Conan. I still have all my notes, someday I might post it...

September 2011:

Got my Apple up and running again. Had a dud RAM chip in the first bank. Found it with a logic probe -- D6 on the 6502 was not toggling while the rest of the data lines were, traced this through the buffers, keyboard MUX and latches to the RAM.

My RAM is a motley collection of chips from all over. This one time, the motherboard fried, and they replaced half the chips, including about half the RAM. Also, some RAM chips blew before, and I replaced it with what I could find.

So this time, I found my stash of 25 brand new 4164 64k x 1 chips. These have four times the capacity of the 4116 chips used in the Apple, and are 5V only parts (the 4116 needs -5V and +12V as well). Replacing 4116 RAM with 4164, 41256, etc_.txt.

From: "Matt Osborn" 
Subject: TECH: Replacing 4116  RAM with 4164, 41256, etc.
Date: Monday, October 23, 2000 12:40 AM

I saw some posts recently about replacing 4116 RAM with 4164,
which is more reliable (it uses only one voltage, not three!) and
is cheaper (if you know where to look!).  I wanted to come up
with a solution that works for all boards (no board hacking or
harness tricks involved).  So here it is:

Take your 4164 chip and bend pin 8 up and over the top of
the chip.  Solder a small wire from that pin to pin 9 (which
is directly across from it, and has +5V on it).  Pin 1 of the
4164 is not used... just snip it off so you don't have to worry
about the -5V on the board.  That's it.  The chip is ready
to plug into the socket of the 4116.

You can do almost the same thing with a 41256 (also known
as TMS4256, MCM6256, HM51256, MB81256, etc., 256k*1).
In addition to flipping up pin 8 and connecting it to pin 9,
bend up pin 1 and connect it to pin 16 (that'll tie the high
address line to ground... you can't leave it floating).

I used TMS4256 to replace some blown out 4116 in my
Juno First, and it works great.  Runs much cooler!!!
Soldering the wires is a little bit of work, but worth the effort.


This works well, and I replaced the first two banks, giving me a "160k Apple(!)" (of which I can of course only use 64k :-) Will upgrade the third bank sometime as well.

September 2019:

A bunch of keys are not working. Not matrix related, all over the show.

This is the UNITRON keyboard PCB after I removed all the keyswitches -- quite unlike the Apple equivalent. Instead of the AY-5-3600 keyboard encoder, it uses a handfull of TTL and a 2732 EPROM.

The interesting thing about this keyboard is that it also has a lower-case mode, sort of. Even though the motherboard does not support lower case. At the lower left, where an Apple ][ has the power light, the Unitron keyboard has a button / light combination.

Super Serial Card

Bought one off eBay. The jumper block has three broken pins.

Apple II Super Serial Card jumper block wiring and connections (jumper block pin 1
matching socket pin 1, "modem")

   1489 pin 3  CTS    1-+ +-16    DB25 pin 8  DCD
                        | |
   DB25 pin 5  CTS    2-+ +-15    1489 pin 4  DCD (via SW1)

   1488 pin 6  RTS    3-+ +-14    DB25 pin 8  DCD
                        | |
   DB25 pin 4  RTS    4-+ +-13    1489 pin 4  DCD (via SW1)

   1489 pin 10 RxD    5-----12    DB25 pin 3  RxD

   DB25 pin 2  TxD    6-----11    1488 pin 8  TxD

   1489 pin 13 DSR    7-----10    DB25 pin 6  DSR

   DB25 pin 20 DTR    8-----9     1488 pin 11 DTR

(This is in the Super Serial Card Installation and Operating Manual, on the schematic page.

Apple II Communications Card


Disk drives and controllers

Apple disk drives, controllers, and the IWM.

There are many badly-scanned schematics for the analog board inside the Disk II. You will find a decent schematic here or in the DOS 3.2 Instruction and Reference Manual on Rich Cini's page -- note that this is the one with R28 = 9k1, other analog boards have R21 = 8k2 in series with a 10k pot R33 "Pulse Width Duration".

More schematics.

Stellation Two The Mill

Somewhere along the way I acquired a The Mill 6809 co-processor. This is not the only 6809 co-processor for the Apple II, there was also the Seikou EXCEL-9, IBS AP-10 and maybe others.


I bought a Catweasel back in 2005. As of 2015 it's still unused.


I found some Wildcard PCBs on eBay.

Commsoft Photocaster

This is some kind of an SSTV system which sends black and white or colour (by scanning the same picture three times with different filters) pictures at a whopping 128 x 128 over a radio link. This cost $500 back in 1983, excluding the actual video camera. See this press release on page 98 of Ham Radio Magazine.

The board I have looks like a clone. I doubt they would have sold a whole lot of them, but at $500 they would have been worth cloning!




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