VOGONS


First post, by BLockOUT

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A friend gave me a small box full of eeproms that were taken from old dead motherboards many years ago.

I have an eeprom flasher, and tried to erase the eeprom using UV light all night but i had no luck.
I tried leaving the uv lightbulb 5mm above the eeprom for 30 minutes, then for 8 hours and nothing changed.

this is the lightbulb i had at hand for uv light.

L%C3%A1mpara_bajo_consumo_luz_negra_en_espiral-15W.jpg

searching online shops around here, an eeprom eraser costs about 80 dollars with timer, and i want to know if there is a cheaper way to get the eeprom erased. What kind of uv light is needed to do the job? I cant belive this is difficult to erase, not even at sunlight can be erased.

Reply 1 of 15, by root42

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Can you post a picture and model number of the EPROM you try to erase? Sure it is an EPROM?

Hackaday has some ideas on how to erase an EPROM using a UV LED:

https://hackaday.com/2018/01/17/improvising-an-eprom-eraser/

If you search eBay for something like "UV nail lamp" you will find small and cheap devices used for nailpolish, but which can also be used to erase EPROMs...

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Reply 2 of 15, by Vipersan

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TBH ..you are better off with a dedicated UV eraser ...
These can be accurately timed ....and produce the correct UV wavelength
and are actually very cheap from China or HK ..
This for example from AliExpress..
https://nl.aliexpress.com/item/NEW-high-speed … iceBeautifyAB=0

another advantage is that the UV light is contained ..
The right intensity and wavelegth in an exposed lamp situation can seriously damage eyes ..permanently.

A lot of 'so called' black light bulbs dont actually produce much if any UV ..
Yes they look like they might work ..but acually only produce very dark purple light ..
The UV component is filtered out.

Last edited by Vipersan on 2018-07-11, 13:51. Edited 1 time in total.

Reply 3 of 15, by AlaricD

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EEPROM should mean that it is *electrically erasable*. EPROMs (or sometimes called UVPROMs) have a small window you must uncover (there will be a label over the window) for using UV to erase them. Perhaps there are some *PROMs that can be erased both electrically or with UV.

But if you haven't uncovered that little window, your UV-ing will surely be for naught.

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Reply 4 of 15, by BLockOUT

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yea its this model

https://www.ebay.com/itm/2-TMS27C010A-12JL-TI … 18285845?_ul=BO

has window and top is ceramic. but it didn´t erase with a lightbulb, i will try to find one of those nail things online

Reply 5 of 15, by BLockOUT

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no luck guys

yesterday i read the article and tried another approach, i had two 5mm UV leds , added a resistor, and connected to a power supply
left the leds touching the eeprom all night , and next morning nothing happened.

I also got a box full of.. not eeproms but flash chips, taken from pcchips and other 586 motherboards and socket7 , different brand motherboards.
Is it safe to replace the TMS27C010A-12JL EEPROM with a flash bios chip like the MX28F1000PPC ?? Or the motherboard would only take the eeprom chip?

im kind of new into epprom and flash chip programing. I remember some time ago a friend told me to save the eeproms from garbage hardware found on trash, but not sure why, are epproms very seek after?

if anyone has knowledge please let me know

Reply 6 of 15, by shamino

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Is it safe to replace the TMS27C010A-12JL EEPROM with a flash bios chip like the MX28F1000PPC ?? Or the motherboard would only take the eeprom chip?

I looked at a couple datasheets (they can usually be found pretty easily by searching the part numbers).
The MX28F1000PPC pinout matches the 27C010 and it runs on the same voltage in read mode (5V). It would most likely work.

One small difference at pin 31. On the MX28F1000PPC, this pin is required to be held at Vih (5V) while reading. On the 27C010 it's "don't care". This means your motherboard might not hold it at 5V as you need it to.
You can use a multimeter to check voltage on pin31 while the system is running, if the system is holding it at 5V then it will meet the requirement of the MX28F1000PPC.

EPROMs and Flash ROMs don't behave exactly the same, but they're very close. I've run into a case where a seemingly compatible Flash ROM did not work in place of an EPROM, but I think that's rare. Given that the pinouts are electrically compatible, there's no danger in trying it.

=========================
Windowed UV EPROMs are EPROMs (one E). EEPROMs (two Es) are "Electrically Erasable", which windowed EPROMs are not (they require exposure to UV).

I'm not sure whether Flash ROMs are technically supposed to be called EEPROMs or not. I thought EEPROMs were classified as a separate type, but I haven't looked much into that subject.
"27" series chips are UV EPROMs. I thought "28" series chips were classed as EEPROMs and "29" series as Flash, but the 28F1000PPC datasheet I looked at is calling itself "Flash". I don't know if they're taking liberties with the terminology or I'm just wrong about there being a distinction.

When you expose an EPROM to UV it resets the bits to "1" values. The programmer selectively sets bits to "0". The way the bits are stored is analog in nature (that's how the world really works), so a badly erased or programmed chip might not give consistent reads in different devices or it might corrupt in less time than a well programmed one.

When you erase a UV EPROM, you should clean the window with alcohol so that it gets good exposure evenly across all the memory cells. If you leave sticker goo on the window then some parts will be harder to erase. When this happens with a real eraser, it can lead to the user extending the erase time and overexposing other parts . Overexposure can make some bits become stuck.

I've read internet comments that you can erase an EPROM by leaving it in the sun for a few weeks. I've never tried it though, and I'm not sure how many of the people who say this have tried it either. I'm sure it works, just no idea how long it would really take. The more directly it's exposed to the sun, the better.

A few years ago I found an old US-made eraser with a metal chassis on eBay for about $30-$35. I think new Chinese ones are routinely available at that price, and that's probably a fine way to go. Due to paranoia about UV exposure I dug to find one from a company with a reputation and address, but I was probably worrying too much. 😀

EPROMs are all out of production as far as I know. Many older devices use them so there is a demand for them. Old arcade game PCBs use tons of them, and that's a high maintenance hobby.
Pricing on eBay can be inconsistent from one part number to the next, it depends which part numbers are flooding the market while others are harder to find. Sometimes substitutes with larger capacity than needed are cheaper than a match to the originals.

Reply 7 of 15, by Tiido

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Completely forget about all sorts of LEDs, lighbulbs and sunlight, they are not going to work from my experience (and lot of others too). Sun will probably only work if you're waaaay south and get loooots of cloudless days, the wavelenghts of UV from sun are not very useful for EPROMs as aren't things you get from LEDs and various UV lightbulbs. Get a dedicated EPROM eraser from ebay, they're not expensive and will work fine, mine cost something like 8usd with shipping. Smelled a bit funny though but over time it disappeared 🤣.

Window of the EPROM must be clean as pointed out earlier, any glue or paper residue will cause problems and you'll likely have bunch of unerased bits scattered around the chip.

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Reply 8 of 15, by shamino

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Yeah, erasing via the sun is probably not feasible. It would take some pretty strong exposure over a long time I think.

I use EPROMs in an old car of mine. Since I consider it an ongoing project and I want to be able to easily erase and reuse the chips, I don't bother covering the windows. I don't think it gets direct sun, but it gets plenty of indirect light (the chip is openly exposed in the cabin at about mid-height next to the driver's shoulder).

I've had a chip in there for over a year that still works fine. The ECM runs a checksum on it at every startup, and if it were corrupt it would be giving a trouble code.

Reply 9 of 15, by SSTV2

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Cheapest way? All you need to be able to shunt charge from floating gate mosfets in eprom is UV (C spectrum) light, which is produced by germicidal lamps. Some ancient kitchen steam collectors used to have those, or you could google your local hardware stores for 4 or 6W standalone germicidal UV lamps (though you'd have to obtain ballasts for their wattage accordingly).

Reply 10 of 15, by stamasd

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For erasing eproms cheaply I use a little fluorescent light fixture (the kind that you stick under kitchen cabinets) that is battery-powered and has an inverter built-in. Takes 4 AA batteries and functions for a long time with a set of them. Got it at Wal-Mart for about $10 a few years ago. It takes 8-inch (20cm) standard fluorescent tubes with socket T5. I then bought from ebay or amazon (don't remember) 8-inch T5 germicidal tubes - they were about $4 each, and installed one in the fixture instead of the normal tube. Works very well, I expose the eproms for 5 minutes at a distance of about 10 inches from the lamp. Total cost for this setup was under $20 (well actually it was more because I bought multiple germicidal tubes so I have spares). I use a 12-inch-tall opaque plastic container; I glued the fixture to the underside of the lid, and place the eproms to be erased at the bottom of the container on a sheet of aluminum foil. Turn it on, put the lid on the container, set a timer for 5 minutes, turn it off, done.

Quick tip: this type of light fixtures have a transparent plastic cover placed over the tube to prevent you from touching it and get an electric shock when it's turned on. That cover absorbs a surprising amount of the UV generated (I ran tests), so I use the light without the plastic cover. Just make sure you don't touch the tube while it's on.

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Reply 11 of 15, by Paralel

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I can reinforce the above, it needs to be UV-C spectrum (100–280nm), and anything marked as "germicidal" will work perfectly, if it is strong enough, which most retail products should be.

Make sure you are wearing eye protection when working in this spectrum, if the light source is in the open, as well as having your skin completely covered. While the UV-C range does not cause cancer, etc... even short term exposure can cause serious skin inflammation and irritation (easy to tell, your skin will turn red, but not like a sunburn, more like when something really irritating touches your skin), and the same can happen to the eyes, but even more serious, causing a condition known as photokeratitis. It is more serious than you think. If it happens a few times, it can be terribly uncomfortable and inconvenient. But if you keep doing it, the damage can be permanent, and then we are talking about true partial or complete blindness. I have actually seen this a few times before with people who worked with UV sources and were never told of the risks involved. I'm sure none of us here will be around an intense enough source long enough to cause this, but better to be safe than sorry. Also, sunglasses won't work, they are rated for UV-A & UV-B, but never UV-C, because UV-C never gets far enough through our atmosphere to reach us.

Last edited by Paralel on 2021-06-06, 01:33. Edited 1 time in total.

Reply 12 of 15, by 133MHz

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As said before, it depends on how cheap you can get a source of UVC light. In my case I lucked out years ago by finding an old small germicidal air purifier for around 6 USD (including the 12V wall wart to run it) at a thrift store - I spent a few more bucks on a project box and stuff to make it tidy and neat but I could've just stuffed the EPROMs I wanted to erase inside the air purifier for maximum thriftiness 😜

Here are some pics from back when I made this:

dscn2517.jpg?h=800 dscn2521.jpg?h=800
dscn2520.jpg?

I transplanted the guts to a project box, added a switch and made a neat little drawer to put the chips into:
cajas_proyecto.jpg?w=600

guias_plasticas.jpg?w=600

borrador_interior.jpg?w=600

borrador_closed.jpg?w=600

borrador_open.jpg?w=600

Nowadays if I didn't have this I'd just get the cheapest already built one on AliExpress at the time, well maybe if I could get a bare UVC bulb for less I'd get that instead, since I discovered that the UVC and the ozone produced by it is really good at disinfecting and deodorizing gross/smelly stuff (taking proper care and blocking all exposure to the light of course).

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Reply 13 of 15, by wiretap

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Necro bump. Just built one of these in a 50cal ammo can.. 25 watts of erasing power. Clears a 27c256 in about a minute 🤣. I can do maybe 30 chips at a time.

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Reply 14 of 15, by pshipkov

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the cheapest way to erase EPROM ?

using shoe sanitizing uv lights that cost few bucks.
my wife being a hygiene "freak" leaves no belonging untrethed, shoes including.

long ago i tried and it worked.
leave the chip facing down one of the uv lights for about 5 minutes.
done.

up to 6 chips can be erased at a time.

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Reply 15 of 15, by Paralel

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wiretap wrote on 2021-06-05, 23:57:

Necro bump. Just built one of these in a 50cal ammo can.. 25 watts of erasing power. Clears a 27c256 in about a minute 🤣. I can do maybe 30 chips at a time.

The sticker is great. I wish more people did this. You never know when someone curious/stupid will flip the switch on something to see what it does.