Defective EPROMs 2764

Discussion in 'Embedded Systems and Microcontrollers' started by takao21203, Jan 2, 2016.

  1. takao21203

    Thread Starter AAC Fanatic!

    Apr 28, 2012
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    Ive found several TI kinds with bit errors often just one single bit.
    They re about 30 years old and have been sold to me erased a mixed lot with different brands.

    Now im trying to see if the bit patterns change from a 8W fluoro tube not UV.

    Ive got both errors for blank check and programming errors as well
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    You need UV to erase, standard ain't gonna cut it.

    Better put them outside for a week or so and let the sun erase them.
     
  3. GopherT

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    Nov 23, 2012
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    Buy a UV LED and hit it for the recommended time x lumens
     
  4. Papabravo

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  5. takao21203

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    OK I know the professional approach normally I get them erased or new.

    Just curiosity. But I think the chips just have degraded equipment in the 1980s wasn't as good.

    The ST chips have no failures.

    The mitsubishi dies are quite large but all have bit errors.

    I use serial flash but deal with older technology if there's demand.
     
  6. DickCappels

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    Aug 21, 2008
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    Ordinary florescent lamps emit UV, to which some people are sensitive. EPROMs are sensitive to it too -and that's why we used to put black tape over the window of an EPROM, otherwise if exposed to florescent lighting they would start to develop errors in a year or two.
     
  7. JohnInTX

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    Jun 26, 2012
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    @Papabravo recalls right. My UV eraser uses a G6T5 6W germicidal UV lamp. Specs say 253.7nm and its a couple of cm from the chips. Another reason for the taped windows is that in early devices at least, the internal transistor drivers were photosensitive. A strobe or flash bulb would corrupt the reads..
     
    Last edited: Jan 5, 2016
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  8. Hypatia's Protege

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    In my experience 'sticky' (i.e. 'permanently' low) bits in UVEPRMOS are reliably 'repaired' via a single 700 Gy exposure (as indicated by a dosimeter of ionization chamber topology ) to bremsstrahlung spectra cresting at a PE ≈ 80keV --- Said procedure restores the devices to reliable read, Program and UV erasability...

    Below is an excerpt of my description of the procedure (on another thread) -- although said reference outlines erasure of windowless 27' series devices - the procedure is the same!:)

    As regards erasure:
    Better make that months to years!:eek:

    A standard UVA florescent (a.k.a 'blacklight', a.k.a. 'Woods lamp') requires circa 60 hours (window in contact with tube) to achieve complete, reliable, erasure -- AFAIK UV LEDs are productive of significantly 'softer' spectra???

    UVC (a.k.a. germicidal) tubes are both inexpensive and readily available in standard (linear) florescent 'form factors' and, hence, applicable to standard florescent fixtures/auxiliary equipment -- In point of fact the tubes are florescents minus the phosphor (do pardon the oxymoron!;)) and fashioned of UV-lucent envelopes (IOW low pressure Hg arc tubes exhibiting a prominent 'line' at 253.7 nm [~4.89 eV] -- UVC thus sourced will 'do the deed' in less than 20 minutes!:):):) --- One word of caution - pretty though it may be - an energized UVC tube is a 'sight for sore eyes' -- literally!!!:eek::eek::eek:

    Note: Safety is solely the responsibility of the reader! --- I will not be responsible for ARS, photokeratitis, 'burns', neoplastic lesions nor any other injury, illness, liability or loss secondary to casual, unskilled, or otherwise negligent application of information presented here! -- Neither will I offer assistance or advice as regards construction of the described apparatus -- thank you for understanding!:)

    Very best regards
    HP:cool:
     
    Last edited: Jan 5, 2016
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  9. GopherT

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    Your recent post on white LED turn-off lag found the same phenomenon of phraseology - the lack of forbidden transitions of phosphorescence was nonexistent there as well.
     
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  10. hp1729

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    Nov 23, 2015
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    UV LEDs in the hard spectrum? Source, please.
     
  11. Hypatia's Protege

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    That was my question -- To my knowledge 'soft UVA' (≈3.5 eV) is about as 'hard' as LEDs get:confused: -- Still, I've an open mind on the subject!:cool:

    Best regards
    HP:)
     
  12. JohnInTX

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    Jun 26, 2012
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    'Germicidal' lamps are also characterized by being made of fused quartz which transmits UV better than the standard borosilicate used in everyday fluorescent lamps.
    A side note: We used lots of them for general disinfecting lab areas and found that they had to be cleaned regularly to remove film build ups from humidity, people-gunk etc. It turned out that the high energy UV dropped a lot with even a little contamination. We did it several times a month or whenever our UV meter showed a drop in effectiveness. I used to clean the tube in my UV eraser for the same reason but probably not necessary..
     
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  13. Hypatia's Protege

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    Indeed:) Hence the emphasized text:
    --- Emphasis added ---
    Were they composed of the glass used in florescent lamps -- they'd be nothing more than azure 'mood lighting':D --- Hence, contrary to common belief, a florescent having a defect in its phosphor coating is not hazardous to the eyes:cool:

    Not surprising! -- Seems relatively pure H2O is one of the few 'common environmental substances' exhibiting a high degree of UV-lucency (hence the liability to 'sunburn' during overcast weather)--- many people are unaware of the fact that 'plain' polycarbonate safety glasses are sufficient to shield their eyes from 350nm down to 80nm (3.54eV -- 15.5ev) - or 'better' --- When they balk -- I don't argue! -- Lest I be held accountable for every ophthalmic complaint (real and imagined) experienced throughout the remainder of their days!:eek::eek::rolleyes:

    As an aside -- As you are likely aware (but many others may not be), UV 'disinfection' does not kill most microbes outright, but, rather, 'sterilizes' them -- trouble is, under the 'right' conditions, visible spectra can 'reactivate' their reproductive function -- something to ponder when purchasing "UV purified" drinking water:rolleyes:

    Best regards
    HP:)
     
    Last edited: Jan 5, 2016
  14. JohnInTX

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    Jun 26, 2012
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    Aye! There are a lot of big words in there missy, and we're but humble posters... I did not know that.
    Thanks and H/T to Captain Barbossa.
     
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  15. Hypatia's Protege

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    I'm unfamiliar with Capt. Barbossa - hence the reference escapes me:confused: -- If, however, the message is that I'm acting a bit of a 'know all' - I genuinely apologize -- Radiology is among my fondest hobbies -- and when I'm on about my hobbies... I'm afraid I tend to behave a bit like the 'Coca Puffs Bird":eek::oops:

     
  16. JohnInTX

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    Captain Barbossa was played by Geoffrey Rush in 'Pirates of the Caribbean'. Its one of my favorite lines from the movie.
    But.. we are going off topic so...
     
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  17. Aleph(0)

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    Mar 14, 2015
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    HP I say a lot better! Like all the way to at least 10kev (which is 120 picometers) but there're probably gaps with PC lenses cuz of actinic interactions in weakly bound organic material above 100ev and maybe florescence and phosphorescence at injurious UV PEs when exciting radiation PE is above 5kev.
    Now I am saying 3mm thick lenses made from alkali silicate glass is good protection from 3.8ev to 10kev without mumbo jumbo qualification:D!

    PS Ha ha! Cereal ad bird is wearing Vulnavia hat:D!
     
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  18. Hypatia's Protege

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    @Aleph(0) -- I enjoin extreme caution as regards sweeping statements in reference to safety considerations! -- Granted! Your comments are correct as stated! Unfortunately we can be absolutely certain of very little where the 'real world' is wont to intrude -- Consider, if you will, the potential effects of unreckoned contaminants within the glass or mislabeling/misformulation of same? (all of which carry the potential for increased lucency or the noted issues with radio-florescence/phosphorescence, etc...)

    The litigious environment that is our society demands that 'safety notes' are best offered merely as advisories with references to official publications for details of practice...

    With genuinely constructive intent
    HP:)

    PS -- My mention of polycarbonate's 'UV-Opacity' was intended as a point of interest -- Though, in retrospect, perhaps I too was 'sailing rather near the wind':rolleyes::rolleyes::rolleyes:
     
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