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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 11th Aug 2017, 11:03 pm   #1
jay_oldstuff
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Default EPROM eraser won't erase.

Ive put this hear as its computer related, and wasn't sure where else to put it.
I have one of those cheep chinease Eprom erasers (mains UV lamp in a box) and have used it for a few years now. I recentely got a number of used 27C64 eproms for a couple of projects i have in mind so tonight I tryed blanking a couple for a project, put them in set timer for 20 min. but still contain there data so gave them 30 min, still the same so grabbed a few from stock incase those i'd baught had gone bad, tried eraseing them but still the same. the lamp is lighting as you can see the light round the drawer but no erasure. has anyone else had this? can the lamps light but fail to emit UV?

Jay
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Old 11th Aug 2017, 11:35 pm   #2
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Default Re: Eprom eraser wont erase

Sounds to me like the UV tube may be on the way out. Be careful to get the right wavelength replacement as I believe there are differences. Someone else on the forum may be a bit more informed than me on this subject.
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Old 12th Aug 2017, 6:30 am   #3
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Default Re: Eprom eraser wont erase

Hi Jay I have an old BT Eprom eraser you can have give me a PM and you can pick it up ( only In Glossop )

Dave
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Old 12th Aug 2017, 7:40 pm   #4
jay_oldstuff
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Default Re: Eprom eraser won't erase

Thats awsome thanks, will send you a PM now.
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Old 13th Aug 2017, 11:07 am   #5
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Default Re: Eprom eraser won't erase

In the 1970's a former colleague who was then working for another company told me that they had found out that you could erase non-erasable eproms by putting them in a microwave oven. This allowed them to use cheap non-erasable eproms in their development lab rather than the expensive UV-erasable type having a quartz window. I think that the type they were using used the same chip type in both the erasable and non-erasable types, the package being the only difference. I don't recall how long a dose was required and have had no experience with eproms myself, whether ancient or modern. Nor do I know whether this technique had any long-term effects on reliability, not an issue in the circumstances in which they were using them.

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Old 13th Aug 2017, 11:07 pm   #6
SiriusHardware
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Default Re: Eprom eraser won't erase

In my (accidental) experience, putting any amount of metal in a microwave is a bad idea as it usually produces a lot of sparks.

Or does that only happen when the metal fragment is more than a certain fraction of a wavelength long?
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Old 14th Aug 2017, 3:50 pm   #7
jay_oldstuff
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Default Re: EPROM eraser won't erase.

Well fokes due to the awsome generosity of a fellow forum member I now have a proper industrial eprom eraser that is built like a tank and will last me years of service.

Regarding using a microwave to wipe EPROMs, It definitely wipes them (see pic below) unfortunately I may have some trouble reprograming it that was three seconds on low power.

You knew at least one of us was going to try it. PP no usable EPROM was harmed it had a bad programing pin and failed verification.
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Old 14th Aug 2017, 3:54 pm   #8
merlinmaxwell
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Default Re: EPROM eraser won't erase.

Takes microwave chips to a whole new level, erased, well at least unreadable.
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Old 14th Aug 2017, 5:52 pm   #9
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Default Re: EPROM eraser won't erase.

I did say I had had no experience with Eproms myself! Perhaps 1970's devices were physically larger and/or more robust.
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Old 15th Aug 2017, 5:18 pm   #10
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Default Re: EPROM eraser won't erase.

I picked up a little cheepo Chinese one that works cost me less than a tenner I think. they look rubbish but do erase correctly as all I try come back blank. if nothing else usefull in an emergancy

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Old 15th Aug 2017, 10:01 pm   #11
jay_oldstuff
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Default Re: EPROM eraser won't erase.

I agree for occassional use they are fine I used mine for a few years occassionaly and it was fine however if you do lots of Eprom work as do I now the tube seems to go bad, replacement tubes from china are only a few quid tho and if I hadnt been offered this commercial one I have now i'd of just got a new tube for my cheepy one.

Jay
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