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EPROM Eraser

...which equates to at least 27000 erasures! no doubt their output will decline slightly over time, but the decades-old tubes mentioned above still do their job perfectly :)
 
Phil_G said:
...which equates to at least 27000 erasures! no doubt their output will decline slightly over time, but the decades-old tubes mentioned above still do their job perfectly :)
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You're absolutely right.
Also consider that for many reasons (removal or failure of the timer), the lamp can remain on for several days: you'll never know how many hours of use a used lamp has.
 
Istarian said:
@hmb The timer is used to turn the lamp on for a fixed amount of time. It's a simple and inexpensive safety measure, as long as it works properly.
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Yes, the purpose of the timer is obvious. However, it is a simple mechanical timer that is not designed to measure any defined length of time, and cannot be reset but instead has to be left to run until it "winds down". Therefore, I just use it along with the power switch to turn the eraser on and then go "by the clock" to know when to turn it off. Generally, that box takes 10-15 minutes to erase most EPROMs.
 
20 minutes total, without stopping the timer I check at 12 minutes or so that the eprom is now blank then give it the remaining time up to 20 minutes.
Some 'active' erasers read the contents continuously whilst erasing, they too gave it a few more minutes after its blank to be sure.
 
Phil_G said:
20 minutes total, without stopping the timer I check at 12 minutes or so that the eprom is now blank then give it the remaining time up to 20 minutes.
Some 'active' erasers read the contents continuously whilst erasing, they too gave it a few more minutes after its blank to be sure.
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What is the correct distance between the EPROM window and the lamp surface?
 
P101 said:
What is the correct distance between the EPROM window and the lamp surface?
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The UV lamp probably emits light in all directions, but without a reflector there is no concentration thereof. So only the photons that travel directly toward the EPROM's 'window' will be useful with respect to erasure.

Consequently you woll probably want the EPROM to be pretty close to the lamp, because the further away it is the fewer photons will hit the precise spot desired.
 
Phil_G said:
The RS eraser tubes are about an inch or so above the chip drawer.
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I was wondering because UV-C emission undergoes inverse quadratic dispersion in relation to distance, which will affect the exposure time: if you double the distance from the lamp, the intensity becomes 1/4.
So, if I expect a distance of half an inch, the time needed should be about 7 minutes.
Correct?
 
jafir said:
I’ve got one like this: https://ebay.us/m/KywY6R
It’s incredibly cheap feeling, and the timer seems very inaccurate.

It seems to work fine, but for fear of burning down my house I’ll only use it if I can keep an eye on it.
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Best not keep an eye on it. The plastic on those things is so thin and of such garbage quality that UV passes right through it. I have one of those that I only used a handful of times and the plastic on both the inside and outside has turned brown from UV damage. the next time I plan on using it, I'm going to coat the entire inside with reflective foil tape.
 
Phil_G said:
20 minutes total, without stopping the timer I check at 12 minutes or so that the eprom is now blank then give it the remaining time up to 20 minutes.
Some 'active' erasers read the contents continuously whilst erasing, they too gave it a few more minutes after its blank to be sure.
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I don't understand.
If your EPROM usually erases in 20 minutes but isn't completely erased after 12 minutes, do you persist with 12-minute sessions?
Is the erasure time cumulative (12 minutes + 12 minutes), or do I need to increase the subsequent exposure time (12 minutes + 20 minutes)?
I remember that many 5-minute sessions didn't erase a single byte.
In practice, does the EPROM store the radiation from subsequent sessions, or does it ignore the absorbed radiation after each session?
 
EPROMs don't store light. The UV erases the cells back to a known state to be written again.

Since the memory cells don't uniformly erase at the same time, you have to keep the UV on the entire chip for an extended period of time so they all erase. You can do read checks every few minutes and watch the data disappear.

But unless you're having an issue, just run the chip for 20 minutes to avoid excessive UV exposure to yourself.
 
GiGaBiTe said:
EPROMs don't store light. The UV erases the cells back to a known state to be written again.

Since the memory cells don't uniformly erase at the same time, you have to keep the UV on the entire chip for an extended period of time so they all erase. You can do read checks every few minutes and watch the data disappear.

But unless you're having an issue, just run the chip for 20 minutes to avoid excessive UV exposure to yourself.
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This is my experience with the TMS2532A EPROM:
5-minute exposure, reading (not blank), 5-minute exposure, reading (not blank), 5-minute exposure, reading (not blank), etc...
After a total of 30 minutes, all the data was still present.
A single exposure for 30 minutes and the EPROM was erased.
 
P101 said:
I don't understand.
If your EPROM usually erases in 20 minutes but isn't completely erased after 12 minutes, do you persist with 12-minute sessions?
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No, after 20 minutes it will definitely be erased. Very very seldom does a stubborn eprom need longer.
Again, I stress, you're way overthinking this and I dont know why. As mentioned before, my other eprom eraser is a striplight from a telephone kiosk, I time that one manually.
In the early days of PIC processors (pre flash) I also used a lot of UV erasable 12C508JW PICS, these were programmed & erased repeatedly through a software development cycle, again using either of these two erasers.
Both erasers have been in regular use for decades. It really isnt that critical, its a simple process, the troubles you describe above might suggest a duff UV tube or unsuitable frequency, or maybe one duff eprom.
If all your eproms behave this way then the UV source is suspect, if not then its just a duff eprom or maybe the window isnt clean.
Bear in mind that the TMS2532A is a notoriously weird eprom - usually avoided for that reason - there is one case I'm aware of that a TMS2532A can be damaged by 25v programming (should be 21v) such that it won't erase fully to all FF states, but I'm assuming you will have tried erasing eproms other than the weird TMS2532A ?
 
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After a lot of programming/erasing cycles the eproms became slower, we cured them in the lab by heating up to 80-100 °C under a normal desk lamp for about 30 minutes. The speed-up was clearly visible (on the cooled-down parts) with a fast scope - dunno what happened to the crystal structure?
 
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