Executing Gummiworms The trials and tribulations of a grumpy curmudgeonly old git

Ghetto eprom erasing

[Note: As we all know cameras and I don't exactly work well together but i've tried to at least get semi-focused shots.]

I have been messing around recently with Psion Organiser2's. I'd wanted one when i was younger and they first came out but I had better things to spend my money on at the time (Girls, Beer and travel). Anyway I recently picked up a couple along with a couple of programpaks, rampaks and some datapaks. The rampaks are just battery backed up SRAM and the you can read/write to them willynilly as much as you like as long as the battery is still functional. Programpaks are normally PROM (or ROM) so you don't really need to worry about writing to them as you can't but the datapaks are EPROMs, so like the rampaks you can read/write to them however there are certain caviats. reading is fine, you can read from them until the cows come home and a couple of months beyond and writing is ok too, it'll drain the battery in the Organiser a  bit but no real problems, where there is a difficulty is that when you delete a file on a datapak it isn't really deleted it's just unlinked, the space isn't freed it's just not available so eventually you will have a datapak that you can no longer write too. When Psion were making and selling the Organiser they also made and sold a datapak eraser that was really just an eprom eraser in a psion labelled box and a 20 minute timer. I don't have one of those and I haven't seen one that runs on American voltages anyway and I no longer have a bog standard eprom eraser either so I needed to either build one or buy one. The thought of buying one does go against the grain for something so simple and the ones on evilbay looked like they either sucked, were unsafe or the drawer for the eproms would be too shallow. So I set about looking for instructions on building one. I found a link to some instructions to building one that looked quite nice http://highfields-arc.6te.net/constructors/other/epromerase.htm but I haven't seen a flashlight like the maplin one in the states for years and i wandered around a few pet stores and medical supply stores in the area and noone had the right tube anyway (i do plan on trying to find the parts to make the one in the link as it looks nicer than my "hack" but for the time being i'll use what I eventually ended up with. Handily enough when I was looking for an eprom eraser hack-a-day had a nice post on using a baby pacifier sanitizer to erase tiny eproms. which looked good, the only trouble is that the psion datapaks are pretty big. about 2.5" by 1.5" by 0.7" roughly. so it wouldn't fit  in that type of sanitizer. So i did some research using the delphic oracle otherwise known as google and found out that as long as you avoid UV leds or currency "black lights" anything that will kill germs is in the range (give or take a few waves) that will erase eproms too, the wavelengths are not exact but cheap electronics will be out of spec just enough that most sanitizing devices like a toothbrush or pacifier shoudl do the trick.  I spent the afternoon on evilbay looking for a baby pacifier sanitizers and found a still in unopened box one that looked quite nice for $15 (expensive i know but cheaper than going to the chemists) and $20 incl. S&H as a BIN. It took about a week to arrive and it arrived broken

Of course I complained to the seller and they refunded part of my money which I accepted as I knew if nothing else it would keep me amused for a few hours trying to fix it and avoid blindness (for me and the cats) So I opened it up and noticed that one of the wires was holding on only by willpower so a small dab of solder on that for a start but it still didn't work so I started looking at the switch and say that when it was out of the case it worked when it was in the case it didn't and that the reason was that the circuit board was slightly bent and wasn't at the right level to be hit but the "flange" on the door. the judicious use of some thin card shims and a slight bit of pressure on the circuit board and all was good, i could blind a cat at 10 paces

Once it was working I put a psion datapak into it and started the UV cycle. The sanitizer I have runs for 6 minutes and then shuts off and you have to open the door and close it again to restart it. I ran it for 10 cycles and put it in the psion Organiser to see if it had been even partially erased, it didn't seem to be but i realised that the datapak probably wasn't near enough the UV source to actually be effected by it. so i started looking around for something to raise it closer to the UV source. I was hoping to find somewher ein my pile of junk a matchbox but I couldn't and the only things that fit in the sanitizer were either a zippo lighter or a few tins of petit mints, blackcurrent and green tea flavour. Two of the tins looked to be about right to raise the datapak to a good height so in they went with the datapak on top and 8 6 minute cycles later (i tested after 4 cycles and the eprom was mostly erased but the header hadn't been zero'ed yet so although the psion said it was empty it couldn't use it. one more cycle would probably have done it (6 total actually seems to be enough to do it properly) i did another 4 cycles.

So now for about $10 I have an eprom eraser that will do in a pinch and defiantly works well for Psion Organiser 2 datapaks.