I had one of the early Jupiter Aces - the
circuit board said something like v1.00 - and it had some added
soldered wires on the board, correcting some errors, but it worked
well enough. Forth was definitely what attracted me to it - I was frustrated with Basic on my Sinclair XZ81, and Forth seemed like a big step forward. And I think it was.

I was 14 or 15 at the time. The first summer I wrote a whole load of games, mostly in Forth, but
sometimes Forth just wasn't fast enough. I got a copy of "Mastering
Machine Code on Your ZX81", and learned Z80 machine code. If there was
an assembler available, I didn't have it, so this was all
hand-assembled. Getting jumps right was a total pain, as was
debugging. Generally, it either worked first time, or you started from
scratch again. Usually I got there in the end.

I sold those games through a ad in "Your Computer" magazine, and
earned back the price of the computer several times. But recording and
shipping tapes one at a time got tedious really fast, so I didn't take
that any further.

My Ace got modified quite a bit over the next couple of years. An extra
16KB RAM pack was an early addition, taking it to a whopping 19KB.
Because Forth was so compact, I never filled that up.

My mother worked for Chubb cash dispensers (ATMs for Americans) at the time, and at some
point they scrapped a lot of equipment. She tipped me off, and we
went round there one evening and liberated lots of cash dispenser
pieces from a skip. Amongst these were several numeric keypads with
lovely mechanical keys. I dismantled several keypads to take out all
the individual keys and made a proper keyboard to replace the original
dead rubber monstrosity.

At school, I was taking O-level Technology, and you had to do a final
year project. I'd seen articles in "Your Computer" about competitions
where a micro-mouse robot would have to find its way through a maze.
That seemed like a cool idea to me, so I decided to make one, despite
not really having much idea how. I hadn't done any digital
electronics at that time, but my friend Johnny Tombs (who later went
on to be a Professor of Electronic Engineering) had decided to make a
parallel I/O port for his ZX Spectrum using TTL logic for his Technology project. I'm not
sure where Johnny learned about digital electronics, but he knew what
he was doing, and designed a nice elegant circuit board and etched it
at home. The Ace had the same Z80A CPU as the Spectrum, so I figured his
design could be adapted. After a lot of pleading, he gave my his
design and spent some time explaining to me how it worked and loaned
me his copy of Watford Electronics catalog. A couple of weeks later
all the components arrived, and I spent a busy few days soldering up
my modified I/O port on veroboard. Compared to Johnny's professional
looking version, mine looked like a mess of wires and chips, but it
worked!

So then when it wasn't playing games, my Ace rode about on the top of
a fairly flaky micromouse, made in the school metalwork shop out of
aluminium sheet, some lego motors, and some light sensors to detect
maze walls, exploring mazes. It didn't win any prizes but it did get
me an A in O-level Technology.

My school was throwing out an old teletype, so I scavenged that. Then
I modified the parallel I/O port to output +/- 12V on one pin, and
wrote software to bit-bang RS232 at 110 baud. Back before the
Internet, just finding the specs for RS232 was not so simple - our
local library was a bit limited in that way - but I got there in the
end. A lot of guesswork and trial and error. I don't think anyone made
a printer for the Ace, so I may have had the only one. Being able to
print code listings really helped, even though the teleprinter only printed capital letters.

Somewhere over the years, with my parents moving house multiple times,
the Ace disappeared. Many years later, I found one on Ebay, and still
have it. But somehow I never fell back in love with it - it just
wasn't as good as I remembered my rather non-stock one being at
that formative time in my life.