How to build your own !
by Grant Searle
Please note that you are NOT allowed to reproduce any of this page elsewhere on the Web without my permission!
This is the second of my "build your own" series of pages devoted to old micros which can still be built since they don't use custom components.
For many years now I have been working with the latest technology using high-powered computers. However, nothing nowadays can replace the time when the first home microcomputers hit the streets. I am a keen collector of the home computer era. Follow this link to see my current collection. In those days you HAD to make your programs fit the hardware and memory available. This added to the enjoyment of programming to see something you had written to fit in a few K spring to life.
The Jupiter Ace has a relatively straightforward design which
makes debugging any hardware faults straightforward. If consists
of the following modules:
The timing for ALL parts of the circuit
The CPU/ROM/RAM area
The display area
I must point out this is not a job for the absolute beginner. You will need to blow your own EPROM image and it will probably be a distinct advantage to have access to an oscilloscope in case it doesn't work. I can assure you the circuit supplied here DOES work without any modifications.
I have, however made the following modifications for my own version:
1. I used a 6264 SRAM to make the program memory 5K instead of
1K. The other 3K is not wasted - it is also available within the
memory map.
2. The original Jupiter Ace used two 4K ROMS. I have used a
single 8K ROM.
3. The Ace uses two 2114s for the display RAM and two 2114s for
the character RAM. I actually had a large amount of 8K x 8 RAMs
in my spares box so, although wasteful, works out cheaper and
construction is slightly easier. The 6116 2K x 8 RAM chips are
also suitable alternatives. Tie any unused address lines to one
of the supply rails.
Construction
The complete computer is built on two pieces of perforated stripboard - one to hold the keyboard and one to hold the rest of the computer. All digital connections are made using wire-wrap wire as this is a lot thinner than conventional hook-up wire so the data and address bundles can be tied to form a neat layout. The positioning of the ICs in relation to each other matches the positioning in the original Ace.
Click
picture to view larger image
Click picture
to view larger image
I recommend printing the circuit out on an A3 sheets if possible. The scan is not perfect but hopefully you should be able to work out any areas which aren't very clear.
Begin construction by positioning the IC sockets (see my pictures below for guidance). Next I recommend wiring the data and address buses for the top half of the circuit. As each wire is soldered it, mark it off on the circuit diagram. This helps avoid any errors resulting from missing connections. Wire in the logic ICs, resistors, capacitors and diodes. As virtually all pins on every IC are to be connected, any errors made will become obvious as more connections are made. For initial testing, there is no need to wire the keyboard into the circuit.
Once all components are soldered and without any ICs inserted into the sockets, connect a continuity tester between the power supply pins. If a short exists then check the underside of the board for any missing track breaks or flakes of copper between tracks. If all is well connect a power supply (current regulated to 500mA if possible). Check the +5V and 0V connections on each IC socket. Turn off the supply and insert the ICs. Turn on the power supply and the television or monitor. If the circuit is working then expect a power consumption of around 280mA. A working circuit should show an small white square in the bottom left of the screen. If all is well then wire in the keyboard if not already done.
Parts list
Component Type
No
Z0 Z80
(cpu)
Z1,Z2 2732 (4K x 8 eprom)
I actually used 2764s in my
design as I had some in my spares box
Z3-Z4 2114 (1K x 4
sram) I recommend using
one 6264 to allow 5K RAM
Z5-Z6 2114 (1K x 4
sram) I recommend using
one cheaper 6116 (2k x 8)
Z7-Z8 2114 (1K x 4
sram) I recommend using
one cheaper 6116 (2k x 8)
Z9-Z11 74LS393
Z14-17 74LS367
Z19 74LS00
Z20 74LS08
Z21,22 74LS11
Z23 74LS86
Z24,25 74LS02
Z26 74LS32
Z27 74LS74
Z28 74LS166
Z29 74LS138
U27 7805 (+5V reg)
X1 6.5 MHz xtal
Q1 2N2369
Q2 2N3904
D1-11 1N4148
C1 39p
ceramic
C2 100p
ceramic
C3 47n
C4 47p
ceramic
C5 -
C6 47n
C7 1u
tantalum
C8 2n2
C9 100u
electrolytic
C10 100n
C11,12 1u tantalum
C13-21 100n
R1 4k7
R2 47k
R3 1k5
R4 1k5
R5 12k
R6 1k
R7 1k8
R8 270
R9 220
R10 10k
R11-23 1k
R24 10k
R25 220k
R26 330
RN1,2 1k x 8
L1 RF choke
LS1 220r speaker My design used a speaker salvaged from an old Spectrum board!
S1-40 SPST switch (keyboard)
JP1 3.5mm socket (audio out)
JP2 3.5mm socket (power in)
JP3 RCA phono (video out)
JP4 3.5mm socket (audio in)
Circuit Diagram
Click here to download the ACE schematics
(Thanks to Bodo Wenzel for supplying me with the schematics. He has redrawn the
schematics using Orcad
here)
Rom image
The ROM image is 8K long
Click here to download the binary image.
(In Internet Explorer,
click using the right-hand mousebutton then select save location
from the menu.)
Keyboard caps
The overlay here is sized to fit into the tops of a standard-size
keyboard You can either resize as necessary.
Click here to get the keyboard overlay at 600 DPI
Pictures of my finished version
Front of PCB
Back of PCB
Keyboard
Acknowledgements
Peter Liebert-Adelt - I couldn't have made it without the
extensive information sent to me - thanks!
Bodo Wenzel - Thanks for the schematics.
Some of my other pages
Build your
own ZX80 - my page showing
you how to build this old micro
|__
ZX80 to
ZX81 conversion - build the NMI generator needed to convert the ZX80 circuit
into a ZX81
|__
ZX80
software - Type in a Space Invaders game into the ZX80
Build your own Jupiter Ace - my page showing
you how to build this old micro
Build your own UK101 - my page showing you how to build
a greatly simplified version of this old micro
Pong - Pictures of
my build of the Atari classic arcade game
My
Machines - My collection of classic 80's micros
I hope this page has been useful.
Grant.
To contact me, my current eMail address can be found here. Please note that this address may change to avoid spam.
