Defective EPROMs 2764

Thread Starter

takao21203

Joined Apr 28, 2012
3,695
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
 

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ErnieM

Joined Apr 24, 2011
8,053
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.
 

GopherT

Joined Nov 23, 2012
8,012
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
Buy a UV LED and hit it for the recommended time x lumens
 

Thread Starter

takao21203

Joined Apr 28, 2012
3,695
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.
 

DickCappels

Joined Aug 21, 2008
6,532
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.
 

JohnInTX

Joined Jun 26, 2012
4,198
IIRC the wavelength of the UV in a comercial erase light needs to be around 253.7 nm to erase them in 15-20 minutes at a distance of a couple of centimeters
@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..
 
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Hypatia's Protege

Joined Mar 1, 2015
3,226
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!:)

...In case anyone is interested, my procedure consists of placement of several devices within the main-beam path at a (mean) distance 20 CM of the collimator (i.e. ~ 40 CM from the beam port) --- thence operation of the tube (large filament at full temp, anode potential a flat 80KV) for a 'dose' of 700 Gy at the lowest (i.e. most distant) tray (approximately 3 minutes with my apparatus). At the stated exposure I have never experienced difficulties with reprogramability , subsequent data retention failure or other reliability issues - despite many cycles --- Though, when I had occasion to sell erased OTPs as 'blanks', I made it a point to advise purchasers that the devices had been erased via 'nonstandard methods' and, further, that anticipated reliability should not be equated to that of new devices (I'll have a gold star, please! ;))

PLEASE NOTE: By 700 Gy, above, I mean that exposure at the end of which an (ion-chamber type) dosimeter registers a 'dose' of 700 Gy --- Which is not to imply that the chips absorbed 700J per KG of Mass!!! --- Dosimeters are 'calibrated ' for organic matter (Spec. human tissue) and are nowhere near accurate for other substances!!! --- Still, it is convenient to use such instruments inasmuch as all (quality) dosimeters exhibit standardized response -- Note also that, while, in principle, any dosimeter technology (responsive to the spectra in question) will suffice, ion chamber based units tend to be the only (commonly available) instruments exhibiting sufficient range. --- Although 700Gy represents a trivial amount of energy, it is, nonetheless, productive of immense biologic effect! Hence the apparent 'hyper sensitivity' of dosimetry instrumentation...
As regards erasure:
Better put them outside for a week or so and let the sun erase them.
Better make that months to years!:eek:

Buy a UV LED and hit it for the recommended time x lumens
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:
 
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JohnInTX

Joined Jun 26, 2012
4,198
In point of fact the tubes are florescents minus the phosphor
'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..
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
'Germicidal' lamps are also characterized by being made of fused quartz which transmits UV better than the standard borosilicate used in everyday fluorescent lamps.
Indeed:) Hence the emphasized text:
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]
--- 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:

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.
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:)
 
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JohnInTX

Joined Jun 26, 2012
4,198
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:
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.
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
Thanks and H/T to Captain Barbossa.
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:

 

Aleph(0)

Joined Mar 14, 2015
597
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'
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!
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
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!
@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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