Highfields Amateur Radio Club
Constructors Corner.
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Make an EPROM eraser.
By Mike Gordan.

This page was originally on Mikes' own site (hosted by Freeserve). The site has now gone and I have been unable to find this project again. I did try his email address as shown on the page (removed while editing) but the message I sent just "bounced". Mike, if you're reading this and you have a new site with this page on it let me know (brian.mw0gkx@ntlworld.com) where it is and I'll remove this page and link direct to yours.

Thanks to the WayBack Machine Internet Archive I was able to retrieve this informative page and host it here.

This project is a useful resource for radio amateurs as some older TNCs use EPROMs and you may wish to alter the programming to update the performance etc. and before you can program the new info you have to erase the old.

This project is also useful for all those Psion Organiser I and Psion Organiser II owners out there who cannot find a Psion DataPak Eraser or an EPROM eraser to format DataPaks. There are some of us (myself included) who do offer a free DataPak erasing service, but for those who want to be independent or do not have someone offering this service in their country, here is that page (as referenced on the Psion Organisier II forum) again.

I have edited the HTML code, where required, to fit in with the W3C validator but the text and images are all Mikes' work.

I've checked the quoted Maplin part numbers and that torch/lamp is not listed any more, it is discontinued, but you may find them at boot sales, second hand shops etc. Maplin order no. ZC10L (Ultraviolet Mini Lantern) is a suitable replacement, the fitted UV tube will still need to be replaced though as it is the wrong light wavelength for erasing EPROMs. The barrel connector is still available with the quoted number but the cost has increased.

The UV lamp doesn't seem to be available from Aquitics Direct any longer either, at least I couldn't find it their website, but a Google search for "G4T5" turned up this one from uvshop.co.uk.

Visitors who would like Psion DataPaks erased, or data held while the Pak is erased then the data returned to the, now empty, Pak can use the above email address or brianperrett@o2.co.uk to contact me for this free service. I am in Cardiff, UK and the service is a personal one, not connected in any way to the Highfields Amateur Radio Club. Alternatively you could check the Free DataPack Erasing Service page on the Psion Organisier II website to see if there is anyone offering the service in your country.

Brian Perrett, MW0GKX, March 2010.

EPROM Eraser Project

Overview - Simple Solutions - Building an Eprom Eraser - Parts List - Construction - Testing - Caveats

view of the finished project



Short wave ultra-violet light is extremely dangerous and can cause permanent damage to eyes and skin. Ultra-violet light sources must be completely screened off when in use. If you are at all unsure about the safety implications, DO NOT attempt any of the DIY solutions suggested here. I accept no responsibility for any harm caused by this project.

Overview, by Mike Gordon

EPROM packages have a transparent mica window which allows the chip to be erased by exposure to short wave ultra-violet radiation. Commercial EPROM erasers which perform this function are typically expensive. However, there are a number of possibilities for low-cost DIY solutions, so long as basic safety precautions are taken.

A Hitachi 2764 EPROM, with mica window for UV erasure.

A Hitachi 2764 EPROM, with mica window for UV erasure.


Simple Solutions

The Sun is a source of UV, and at a pinch sunlight can be used to erase EPROMs. Typically 24 hours of continuous sunlight are needed for complete erasure, which is inconvenient to say the least! If you have nothing else to hand, though, it may be worth a try.

The old-style mercury sun lamps are a better bet. They are no longer sold as they are considered dangerous, but are a common find at boot sales and the like. Place the EPROM around half an inch from the light source (don't get too close to it yourself!) and you can expect an erasure time of an hour or so.

The modern type of sunbed/solarium is probably less effective - by all means try it if you have one. (You may get some strange looks if you try this at your local leisure centre!)

The safe, "black light" UV sources, as used in money testers and nightclub lighting, are useless for erasing EPROMs, as are normal incandescent lights and fluorescent fittings.


Building an EPROM Eraser

The best solution is to build an EPROM eraser incorporating a short wave germicidal UV tube as the source, with a cheap pocket fluorescent torch providing the necessary electronics. This type of tube is very dangerous and can't be used unscreened, as shown below. An enclosure is needed, plus a means of switching on the torch without opening the box.

The G4T5 Germicidal UV Tube.

The G4T5 Germicidal UV Tube.


Parts List




Maplin Code

Maplin Price (ea.)

Total Price

4 Watt Fluorescent Lamp 1 YT10L 4.99 4.99
2.1mm Barrel Connector 1 JK11M 0.85 0.85

Both were obtained from Maplin in the UK.

The fluorescent torch, with UV tube and power connector in place.

The fluorescent torch, with UV tube and power connector in place.

Also needed are an external plug-pack 6 volt DC supply for powering the lamp (any cheap universal type is suitable), a plastic Amaray style VHS case (an opaque one, not the transparent type!), some wire to connect to the battery terminals, and some sticky pads or similar to mount the torch inside the case. (Don't use Blu-Tack like I did! It isn't UV-friendly and gives off an unpleasant smell.)

The UV tube is a 4 watt germicidal UV tube, type G4T5, which is a direct replacement for the F4T5 fluorescent tube used in the torch itself. It was obtained from Aquatics Direct as a replacement part for pond treatment units. The online site doesn't allow you to search by part number - instead search for "Bulb", and the part will appear as "4W REPLACEMENT BULB" under "UVC Spares".



Open up the torch as indicated on its packaging, and remove the fluorescent tube. Remove the battery cover and the black plastic end cap it attaches to, then split the two orange plastic halves - the torch should come apart quite easily. Solder a pair of wires to the battery terminals, remembering which was positive and which negative. Solder the other ends to the DC barrel connector.

Reassemble the torch, minus the clear plastic shield and the battery cover, and re-fit the fluorescent tube (do not fit the UV tube as yet). Put the power switch in the "fluorescent on" position and connect the torch to your 6v DC supply. The tube should light up - if it doesn't, try reversing the polarity of the supply.

The "Amarayser" ready for use!

The "Amarayser" ready for use!

Now disconnect the power, remove the tube and fit the UV tube in its place - it should be an exact fit. Attach the torch inside your VHS box, as shown, and route the wire outside the case. (If there is no suitable notch to route the wire through, then create one using a file!) Use electrical tape to secure the wire in position.



Place the EPROM(s) to be erased on top of the tube, then close the box. (The box should be just deep enough to allow you to close it with the chips in place.) Connect up the supply (NEVER do this when the box is open!!!) - erasure should take around 10 minutes, but allow 15. Disconnect the supply, open up the box, and remove the chips. Now verify that they are blank, using your programmer's "Blank Check" setting.

That's it! Your EPROMs can now be erased and rewritten as many times as necessary.


Some Caveats


This page (was) maintained by Mike Gordon. Last updated 14th July 2000.

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