Building a Jupiter Ace

What is the purpose of building a Jupiter Ace ?

The aim was obtain atleast one more test machine but the cost of a Jupiter Aces are well out of reach of so I decided maybe I could build one.... hmmm -

The Great Idea!
I had previously done digital electronics and micros back in college and had some hands on PCB development, My soldering skills where a tad rusty to say the least! ? But how hard can it be right ?

Components Check
Using an existing Ace I listed all the components I would need just so I could make sure they were still availible off the shelf, The first hurdle most were still availiable, many where second hand and some took weeks to track down and import.
Knowing I could obtain the components albeit spread aroud the globe I decided to go on, I now needed a circuit to follow, most of the info on the net covering the build of a Jupiter Ace used alternative components and thus alternative wiring layout, I needed the Ace to be an exact replica of the original and not change the circuit so I thought the best way was to use the original PCB layout.. I photographed the Aces I had but I still couldnt be sure of the circuit beneath the ICs and then as luck would have it I found a guy who had an unpopulated board!

Drawing the PCB
Using the PCB scans I redrew the entire circuit top and bottom at 600dpi, The completed drawings would be a direct replica of the original Jupiter Ace PCB, over 9000+ lines and pads, including the original errors and re-routing attempts! Just for authenticity. I independently drew the TOP layer then added the approximate 700+ hole positions of varying sizes, I then drew the bottom layer and aligned each whole and track again all by hand, this took some time to draw this and constantly checking for missing/ incorrect traces, and I still missed 1!!! - Ive not done the drawings in CAD so all modifications would have to be re-made by hand like the original drawing.

A couple of weeks later when I finally finished the drawings!

Jupiter Ace PCB


Transfering the Circuit to Copper Clad Board
And now I needed to create this into a board of copper traces, I read various articles on methods to print and transfer the print to the copper clad board, I brought a laser printer from a carboot and tested printing on various papers and ironing it on to the copper board, all where failed attempts...

Toner transfer Method (my failings!)
The idea is you print your circuit mirrored onto a piece of paper which you then iron upside down onto the copper board, the toner from the laser printer is reheated by the iron melts onto the copper board you then soak the board in water for sometime the paper breaks away and leaves the toner on the copper board, the toner is plastic and resists the etching process to leave the traces behind, once etched you use acetone and wire wool to remove the toner.. all sounds good so I thought id give it all a try how hard can it be... it apears its all reliant on each part of the process being exact... the paper: if it doesnt break up easily enough in water then it will pull the toner away from the board, If a paper leaves some fibers behind then the etching may not work well and leave lots of dots and bridges of copper between tracks! I tried lots of different papers some better thn others all with no luck, If youre iron is too hot in the same area for too long or too much pressure then the tracks smudge and blend, if its not hot enough or consistent to transfer in the same place or the pressure isnt enough then toner wont bind to the copper board, However I did manage to do this process on a small board of 2 Inch square single sided board but when I came to the Ace 7.5 * 8.5 Inch double sided it wasnt going to work so I needed to look at an alternative..

UV Sensitive Board or Press n Peel
I really wanted to go with UV sensistive copperboard but this would require buying an expensive UV exposure unit or building one (even more time) also this woulding use up the copper clad board I brought so I thought I would buy some press n peel (again expensive) at £19 for 5 sheets may not be too bad for small single sided board but I would need to use 1 sheet per side! I tested the circuit printout onto A4 paper to find not only did the print not fit on A4 as the printer wouldnt print right to the edge but worst of all when held up to the light to check the circuit lined up which they didnt! the inacuracy of the printer meant each time the print was slightly different some times compressed or stretched!

I knew now it was going to be hit and miss the first "press n peel" sheet jammed in the printer, the next 2 worked I could see they didnt line up in areas but made the decision to go with it as I couldnt see it was going to get much better!

Jupiter Ace Circuit
Note: printed landscape as circuit is A4 Width and my carboot laster printer won't print to the edge!

So I lined the wholes up best I could and stapled the edges I sandwich'd the copper clad board in the middle and ironed it being careful not to move it and turning it to heat both sides evenly, the majority of the circuit came out some of the dark areas I needed to pen in with a permenant marker.

Jupiter Ace Top
Top: Double sidded copper clad with Press n Peel ironed on ready for etching

Jupiter Ace Bottom
Bottom: Double sidded copper clad with Press n Peel ironed on ready for etching
note: the board will need cutting down afterwards.

I did the etching outside in the fresh air on a warm dry day (you must remember we dont have that many).
I prepared 1 ltr of clear PCB etchent suspended in a tray over hot water to achive an approximate temperature of 45C reported best working temperature of the etchent, It was far from the most corrosive chemical but this slower acting method does allow for greater control of not over eroding the smaller traces away, This process took around 20 minutes to complete, all the time the solution was kept moving to evenly etch the board, and the board turned over periodically.

freshly etched PCB

Once cleaned off, I used Acetone and wirewool to clean away the press n peel and ink to reveal the copper.
Jupiter Ace Remove Ink

Now I cut the slots for the expansion ports and the 2 case relief cut outs
PCB cleaned and cut to size.

Using a multitool and a homebrew clampe on a drill post I used a 0.8mm drill and drilled all the pads, these are for all the pins for vias, components, caps, resistors, ICs etc... some +800 odd holes later and maybe 3 drill bits later!

Drilling PCB holes

Now studying the circuit and a genuine ace I soldered all the vias in place using legs of resistors to connect the top and bottom layers, I checked the connection with a multimeter as I went as some connection didnt go to the right places from top to bottom layers as pointed out earlier so some tracks had to be cut away and resoldered. (a huge issue!)

Soldering Viasa

Then I needed to connect the IC sockets to the top and bottom layers, geting a soldering iron to  the top layer once the socket is in place is impossible as the socekts sit flush with the PCB, After reading various methods I went with using turned pin socekts,
Turned Pins IC Sockets

Turned pin sockets have long pins which are stepped this is still difficult to solder a track under the sockets so the idea is to snap away all the plastic and solder each pin indivisually! After extracting +700 pins I soldered them in some 2 weeks later I was done!

Jupiter Ace Components
The components

I then soldered in all the components and plugged in all the ICs.

Homebrew Jupiter Ace
finished build of the Jupiter Ace Replica.

Original Ace for comparison.( im quite pleased! )

Fault Finding!
To be continued ....

Complete Jupiter Ace

Jupiter ACE Chips

How can I help ?
Donations are greatly appreciated!
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Jupiter Ace Cassette Tapes Database

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Thanks for reading, please if you can help out do so - Enjoy microemulator Team.

Key Points

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Jupiter Ace Cassette Database

In order to maximise the database we need to find as many cassettes as possible, from unknown ones to ones known but we are unable to locate.

If you can help us with any old cassettes you may have in the loft you no longer want or know someone that has then please contact us and give them to a good home, If we can't get there in person we can get them collected by courier - please don't throw them!

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Free Jupiter Ace Emulator for Windows

It emulates all known Jupiter Ace behaviour, Inc. Z80 (doc'd and undoc'd), Screen, Memory access, Ram packs, Audio tape files, Tape deck emulation, Sound, Forth, Snapshot saving and loading and more ...

The Jupiter Ace emulator is an attempt to preserve this old micro for all to enjoy.


Microsoft Windows 7, Vista, XP
( XP requires microsoft .net framework )

NO install required, and NO registry garbage.

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Latest Version 1.0.4247 Build: 37209 (5466)