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Jupiter ACE Case restoration by R Liddiard

Please see the Note from the Archive team about this project.

case Recently I purchased a Jupiter Ace computer on the internet. The keyboard worked well and it gave a very clear and stable output on a television screen, but the case had gone very yellow with dark patches especially around the power supply socket and the rivets. There were a few scuff marks as well. At the rear of the case one corner had been damaged and a previous owner had drilled a hole in the right hand side to fit a video socket.

The 9v cable from the power supply (original) had been changed in the past to a red and black one and it had a break in it - repaired and wrapped in plastic tape. Some TLC was needed, so I embarked on a restoration programme.

Following the instructions given in the Jupiter Ace Resource website I "tore down" the computer and removed the case top (see here). Noticeable was the colour inside the top - the very pale cream colour (almost white) of the original styrene. Back in the 1980s bromine was added to the styrene to make it less flammable. Over the years the bromine darkens in ultraviolet light - a problem that appears to be exacerbated in areas where the case gets hot. Most computer cases from this era have darkened with age, but it's surprisingly easy to restore the original colour. Some sources recommend removing any scuff marks using isopropyl alcohol (rubbing alcohol), but it can dissolve the black and red logo so if you do use it keep it well away from that area. I suggest you have a go at restoring the original colour of the case first - it might remove the scuff marks anyway!


Restoring the case's original colour was remarkably straightforward. You will need some 40 volumes hydrogen peroxide paste - available on line (Note). It's usually used for bleaching hair. You won't need much. You must wear plastic gloves to handle this stuff. Luckily, peroxide has no adverse effect on the red and black logo or on the printed strip on the keyboard, so there's no need to mask anything off. You'll need a source of ultraviolet light. I used a hand held battery device used for checking bank notes. You can use sunlight, but it takes about 6 hours, whereas a ultraviolet lamp only takes an hour (about the life of the AA batteries which power it). You'll also need a container lined with aluminium foil to ensure the light is dispersed evenly over the computer case, to avoid a patchy result. I used a foil turkey roasting tin with another piece of foil over the top.

Paint the case with a generous layer of peroxide paste and if you're using sunlight, cover it with clingfilm so it doesn't dry out. Using a UV lamp you don't need the clingfilm - just place it in the container lined with foil. Suspend the lamp about 5cm over the case and slightly to one end of the container. Place the other sheet of foil over the top, so no light can escape. Don't look at the UV light; it can severely damage your eyes. Switch on the lamp for an hour, turning the case through 90º every 15 minutes to ensure every part of the case gets illuminated evenly. Then wash the paste off. You can repeat the process on any stubborn areas. The case should end up like new.

The next task was to repair the damage to the case and fill the hole which a previous owner had drilled in it. The obvious solution was to use 2 part epoxy resin which was fine on the inside but it usually has a unsightly brown colour so if it's going anywhere where it'll show it'll need an additive to make it white. I tried mixing the resin with different samples of paint (undercoat, radiator paint, white gloss, satin and emulsion) but the results were poor. I finally tried Tippex (typing correction fluid) which gave excellent results despite being water based - it just took much longer to harden. I used 2 parts Tippex, 1 part epoxy resin and 1 part hardener all mixed together thoroughly. Putting the case on a cloth on a radiator made it harden more quickly, but I found it best to leave it overnight anyway. When the epoxy resin was hard I removed the excess with a sharp knife and very fine emery paper. Any scratches can be filled using white wood repair wax and then polished off.


Meanwhile I un-soldered and removed the rogue video connector from the printed circuit board and replaced the power supply cable with a new black and black/white one. I took the trouble to power up the computer without its case, using the original power supply.

The voltage regulator was very hot - hence the dark patches on the case. The power supply (an original) is supposed to give a working supply of 9 volts - it actually produced 10.8 volts, so the poor regulator was producing 44% more heat than it needed to. The computer takes a load of about 640 mA so at 10.8 volts it generates just under 7 Watts of heat, over half of which is dissipated by the voltage regulator.

Using a bench power supply I also established that the computer worked perfectly well with a power supply as low as 7 volts and the voltage regulator hardly got warm at all. To preserve the life of the computer and to avoid "heat spots" on the case, I think I'll use a modern power supply at 8v which will be fine if I don't use peripherals which take a heavy current. I also put some heat transfer compound between the voltage regulator and its heat sink, which should help to dissipate the heat more evenly within the computer.

Finally I reassembled the case and printed circuit board and I now have a fully working Jupiter Ace which looks like new

Note: The Jupiter ACE Archive Team would like warning you of the following.

If you decide to restore a Jupiter ACE case using the information in this article then you do so at your own risk. It could make the Jupiter ACE case more prone to damage.

40 Volume is a is Hair Trade description of Hydrogen Peroxide , normally around 12% in saturation and should be used with caution. There are many computer case restoration projects using Hydrogen Peroxide to reverse case yellowing, and you should conduct more research.

Hydrogen Peroxide - Keep out of reach of children and pets. We advise, and it is stated on the product instructions, even if they have used the product before, as that ensures they will achieve the right result. Avoid contact with skin and eyes. Always use suitable gloves