Suspect ATMEL AT28C256 marked EEPROMs

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1024MAK
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Suspect ATMEL AT28C256 marked EEPROMs

Postby 1024MAK » Sat Apr 30, 2016 11:35 pm

Earlier this month, I bought five of what I thought were ATMEL AT28C256 EEPROMs from an eBay seller.
I have also bought some of the same chips from a forum member.

After Colin reported problems in this thread, I thought it was a good idea to do some tests. As I have not got around to making a Beeb EEPROM friendly, I have used my EPROM/EEPROM programmer.

So far I have only tested one of each type. But already there are differences.

This is the first of the five from the eBay seller:-
image.jpeg
eBay 28C256 #1 top
image.jpeg
eBay 28C256 #1 bottom

The silicon signature test resulted in the programmer reporting "No signature found", so I set the chip type manually.
A check to see if the chip was blank gave "Blank ROM"
I then checked the whole EEPROM contents, it all comes back as 0xFF.

I then attempted to program the first eight bytes with a number sequence of 01 to 08.
The programmer reports that the programming failed :(. All eight locations still have FF instead of the number sequence of 01 to 08. I then went to the Data Protection setting function, it said protection was off. But to be sure, I set it to on, then again to off. I then tried programming again. But there was no difference :evil:.

So then I tried with a ATMEL AT28C256 EEPROM from Dave H. Now, I believe he may test the chips he supplies. Hopefully he will reply in this thread. Anyway, the chips he supplies look like this:-
image.jpeg
Dave H.'s 28C256 #1 top
image.jpeg
Dave H.'s 28C256 #1 Bottom

The silicon signature test resulted in the programmer reporting "Signature: 1916", "No match found". So I set the chip type manually.
A check to see if the chip was blank gave "Will burn" :D.
I then checked the whole EEPROM contents, it all comes back as 0x00.

I then attempted to program the first eight bytes with a number sequence of 01 to 08.
The programmer reports that the programming was successful. All eight locations have been programmed correctly :D.

I will try some of the other chips later...

Mark
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby daveejhitchins » Sun May 01, 2016 7:33 am

I do purchase my ATMEL AT28C256 parts from China, via a broker. Why . . . Because it's very difficult and expensive to obtain the genuine parts. I've built-up a good relationship with the supplier: Chip- E-Go here. I test every part I receive. Why . . . Because I know and understand that the parts are not genuine! But do work in the projects I use them in. I get failures, which are replaced every time.

Testing each part is very time consuming, but absolutely necessary. RAM, EEPROM, 6502, GAL16V8 and GAL22V10 are fairly quick and straight forward. WD1772s take more time and produce the highest failures. In fact, even these, are getting hard to find - I may have trouble get further supplies! I have some 6522s that I haven't yet tested, as I don't have a jig for that purpose. I do sell these untested. I've not had a failure yet [-o< However, I will replace any none working parts.

How do I know these parts are't genuine? As Mark has pointed out, the manufacturers part ID is either missing or incorrect! There's, probably, two reasons for this: (1) the parts are copies (2) the parts are from other manufacturers e.g. I've had some parts that show as TI yet are marked Lattice. There could be other sources: Manufacturers rejects and pulled and refurbished (they're very good at this. There are even some videos around showing how they do it!).

So, we have a problem! Parts are getting VERY hard to find . . . and it's not going to get any better. If you can find genuine parts, you'll pay a high price. The alternative is to buy in bulk from a good supplier who'll replace any defective parts - but be prepared to throughly test every part.

p.s. Testing every part doesn't guarantee they'll fully work in your project. As Phill (prime) found out recently with some GAL22V10s I'd supplied him. I replaced them, of course . . .

Dave H :D

Testing: One of my programmers will test RAM by filling with AA then 55, verifying each time. EEPROMs are tested by filling with a random generated image, then verifying. GALs are programmed and verified with a genuine file - I could improve this test if I knew how to build the test file to go with them :oops: 6502s and 1772s are tested in a ZIF socket in an Electron and an AP3/4 respectively. As mentioned above, I need a jig, and software, to test the 6522s - I do have one of MartinBs UPURS boards that I could use, if I had the software (any volunteers?). I also have some DRAMs for A3000 4MB Memory upgrades - does anyone have a circuit I could use to test these with? They're TC514400AZ-60 parts. Thanks
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Sun May 01, 2016 9:31 am

^flip, these carbon copy comes out sloppy numpties :twisted:
Dave wrote:have one of MartinBs UPURS boards that I could use, if I had the software (any volunteers?)

the manual & info is here:
http://www.retro-kit.co.uk/page.cfm/con ... RAM-board/
and I think this is the newest rom Martin put out for test, but will have to check against what's in mine later.... & pics of 'crap' EEPROMS :cry:
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby daveejhitchins » Sun May 01, 2016 9:35 am

CMcDougall wrote:^flip, these carbon copy comes out sloppy numpties :twisted:
Dave wrote:have one of MartinBs UPURS boards that I could use, if I had the software (any volunteers?)

the manual & info is here:
http://www.retro-kit.co.uk/page.cfm/con ... RAM-board/
and I think this is the newest rom Martin put out for test, but will have to check against what's in mine later.... & pics of 'crap' EEPROMS :cry:
Thanks, Col . . . I was thinking more of software to 'exercise' the 6522, to make sure it was fully functional!

If you want me to test your EEPROMs for you, just drop them in the post (2nd class). I can replace any that don't work!

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby danielj » Sun May 01, 2016 10:10 am

So I've got two varieties from the chinese ebay seller, all with the 1315 date stamp. All seem to work - some have the half-moon pin 1 mark, some just a dot next to pin one. Some appear to have writing covered up on the bottom. Will attack with acetone later and see if I can uncover anything. All of them have splayed pins, and all are bright, but could just have been "tinned".

d.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Sun May 01, 2016 12:11 pm

i have an other amtel at28c256 15pu 1207 ? other side 1j7524-1-19802c, 1-p1207 e3 , looks like fake on the top , but not fake on the other side :)

i do program them in my eprom programmer at 5 volt 50msec. like a eprom because my eprom programmer is build that way. an other project in 1986. with 21volt,12,5 and now 5 volt all from 5 volt userport

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby danielj » Sun May 01, 2016 12:43 pm

Application of a bit of acetone to the underside...

DSC_1860.JPG


Can anyone interpret the codes?

d.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Sun May 01, 2016 1:03 pm

Dave wrote: I can replace any that don't work!

Sounds good, how do you manage that, just send them back to China, and say in your batch!? (email later...)
I have 2 out of 5 that failed, not that bad for £3.30 :|
eeproms2errs.jpg

& pic of original from MartinB when he first started this madness :) & the 5 'copy's
as can be seen, the white annotation printing is off (or there silk screen /paint was crap!)
eep5.jpg

So these 4 work fine in the eUPURS board with Read only jumper on!
In my ADI, even the good original one still hangs machine :?
ImageImageImage

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby daveejhitchins » Sun May 01, 2016 2:07 pm

CMcDougall wrote:Sounds good, how do you manage that, just send them back to China, and say in your batch!? (email later...)
I have 2 out of 5 that failed, not that bad for £3.30
I think you need to contact the eBay seller and inform them that you have parts that are not working . . . Maybe suggest that they test them before shipping! and, of course,
give some negative feedback (after giving the seller time to replace the duff ones you have).

Anyway, pop the ones you have in the post and I'll give them a thorough testing.

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby 1024MAK » Sun May 08, 2016 11:35 pm

1024MAK wrote:Earlier this month, I bought five of what I thought were ATMEL AT28C256 EEPROMs from an eBay seller. <Snip>

Okay, I have now tested all five of the chips from eBay and both of the chips from Dave H :D

On ALL of the five chips from eBay, the silicon signature test resulted in the programmer reporting "No signature found".
On ALL of the five chips from eBay, a check to see if the chip was blank gave "Blank ROM"
On ALL of the five chips from eBay, I then checked the whole EEPROM contents, it all comes back as 0xFF.

On ALL of the five chips from eBay, I then attempted to program the first eight bytes with a number sequence of 01 to 08.
On ALL of the five chips from eBay, the programmer reports that the programming failed :(. All eight locations still have FF instead of the number sequence of 01 to 08. I then went to the Data Protection setting function, it said protection was off. But to be sure, I set it to on, then again to off. I then tried programming again. But there was no difference on any of the eBay chips :evil:.

Both the ATMEL AT28C256 EEPROM chips supplied by Dave H :D worked correctly (see my earlier post for details, the second chip gave the same results).

Pictures:-
AT28C256-15PU tops of eBay 1 to eBay 4 labelled.jpg
AT28C256-15PU tops of eBay 3 to DH2 labelled.jpg
AT28C256-15PU bottoms of eBay 1 to eBay 3 labelled.jpg
AT28C256-15PU bottoms of eBay 3 to eBay 5 labelled.jpg
AT28C256-15PU bottoms of eBay 4 to DH 2 labelled.jpg


Mark
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby 1024MAK » Sun May 08, 2016 11:55 pm

More pictures of the underside of the eBay chips that have lettering:-
AT28C256-15PU bottom of eBay 3.jpg
Bottom of eBay 3

AT28C256-15PU bottom of eBay 5.jpg
Bottom of eBay 5

AT28C256-15PU bottoms of eBay 4 to DH 1.jpg
Bottoms of eBay 4, 5 and DH 1

Notice that the moulding marks are all different as well, even though the printing on the top of the eBay chips is all the same...

Needless to say, I am asking the eBay seller for a refund in full.

Mark
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Mon May 09, 2016 6:09 am

did you check if you can program them with 50msec pulse ? i think i have a fake one but can program it with 50msec pulse like the old eprom , but then at 5 volt :)

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby MartinB » Mon May 09, 2016 6:33 am

EEproms don't have a dependency on a programming pulse in the way that UV Eproms do. Once a write is initiated on the falling edge of nWE with stable address and data, the write will complete automatically with no further reliance on the host. For high-integrity programming, the host algorithm should poll the device after a write using data-toggling and wait for the eeprom to complete the given write. If a non-interactive (dumb) algorithm is used based on a time-delay only, then this must wait for a period significantly in excess of the spec. write-cycle time. A delay-only algorithm set to say 5ms may well fail compared to one using say 50ms but this is not the correct way to deal with eeproms. My e-squared utilities (e.g. *EELOAD) for example use data-polling and so are immune to chip specification timing and will work with the fastest or slowest of eeprom devices.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Mon May 09, 2016 6:39 am

that is the theory :) , but if you have fake eeproms that fail maybe you can do the unlogical thing and program if they are eproms, if the fake one's are to be programmed this way , we have new eeproms :) uvproms with vpp 5volt :mrgreen:

MartinB wrote:EEproms don't have a dependency on a programming pulse in the way that UV Eproms do. Once a write is initiated on the falling edge of nWE with stable address and data, the write will complete automatically with no further reliance on the host. For high-integrity programming, the host algorithm should poll the device after a write using data-toggling and wait for the eeprom to complete the given write. If a non-interactive (dumb) algorithm is used based on a time-delay only, then this must wait for a period significantly in excess of the spec. write-cycle time. A delay-only algorithm set to say 5ms may well fail compared to one using say 50ms but this is not the correct way to deal with eeproms. My e-squared utilities (e.g. *EELOAD) for example use data-polling and so are immune to chip specification timing and will work with the fastest or slowest of eeprom devices.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby MartinB » Mon May 09, 2016 6:44 am

Ok duikkie, then if your theory is correct and they are actually eproms, to erase them you will also need to drill a hole in the top and fit a UV lens window.... :wink:

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Mon May 09, 2016 7:26 am

Try it before you die

MartinB wrote:Ok duikkie, then if your theory is correct and they are actually eproms, to erase them you will also need to drill a hole in the top and fit a UV lens window.... :wink:

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby DutchAcorn » Mon May 09, 2016 7:43 am

Is there a blacklist / whitelist of sellers?

I received 10 (in two separate sales) from "h-quality_electronic", they are all fine.
Paul

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby 1024MAK » Mon May 09, 2016 8:11 am

DutchAcorn wrote:Is there a blacklist / whitelist of sellers?

I received 10 (in two separate sales) from "h-quality_electronic", they are all fine.

No, I am not aware of either a blacklist or a whitelist.

It may simply be that "h-quality_electronic" bought batches from various places and some were fakes. So luck of the draw.
Any chance you can post pictures?

To clarify one point: I used a professional Dataman S4 programmer manually set to "Atmel 28C256, 5V Burn, Data Polling" (a stored configuration in the programmer), so this should program to the manufacturers specification. And as it worked okay with the EEPROMs that Dave H :D supplied, I have no reason to believe there is anything wrong with this configuration.

Now, the chips that failed could be PROMs (windowless EPROMs), or another make/type of EEPROM. But whatever they are, they clearly are not what I ordered. If they were relatively new "re-manufactured" pulls, I would have expected a result from the silicon signature test. But either they don’t have a silicon signature to read, or the silicon signature data was erased.

Of the modern EPROMs that I have, the silicon signature test works and gives the correct details (Philips 27C256, TI 27C256, National 27C256B, SGS-Thomson 27C256B).

Mark
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Mon May 09, 2016 8:21 am

it is fake :) , so who knows what the chip is, china bakkery. whole china bakes :lol:

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby paulb » Mon May 09, 2016 9:31 am

duikkie wrote:whole china bakes :lol:


Sounds like a translation of the Dutch name for that baking show on television (it's called "Hele Norge Baker" in Norway).

"Bakers to your fabs!" :lol:

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby Prime » Mon May 09, 2016 9:34 am

This illustrates why I am very reluctant to buy electronic components for use in boards that i produce from ebay, unless the seller is a know reliable seller (such as say Telec).

Especially as you can still buy 28c256s from farnell, yes they are more expensive, but in the end there will be less faffing about wondering if they are fake. Worse still if they appear ok when you program them but fail when they get to the customer.

Cheers.

Phill.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Mon May 09, 2016 10:48 am

sounds like : someone can not hold there .... load ? :)

Prime wrote:This illustrates why I am very reluctant to buy electronic components for use in boards that i produce from ebay, unless the seller is a know reliable seller (such as say Telec).

Especially as you can still buy 28c256s from farnell, yes they are more expensive, but in the end there will be less faffing about wondering if they are fake. Worse still if they appear ok when you program them but fail when they get to the customer.

Cheers.

Phill.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby DutchAcorn » Mon May 09, 2016 6:54 pm

1024MAK wrote:...Any chance you can post pictures? ...
Attachments
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby 1024MAK » Mon May 09, 2016 7:49 pm

So, unless anyone can see another pattern, it looks like chips that have no moulding marks on the underside, or which have a moulding mark with TAIWAN on the bottom don't work.

Whereas chips that have a moulding mark with KOREA or PHILIPPINES (I think that's what's on one, maybe two of Daniel's) on the bottom do work.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Mon May 09, 2016 8:13 pm

I got my 5 from 'h-quality_electronic', cost £3.28
eBay messaged them about my faulty 2, they first said :
"dear customer
we are sorry to hear that
could you please kindly try to change a programmer to test it again ?
if it still have problem
send message to us
we will take action at once
thanks
regards"
as I don't think they knew what my pic of my elk setup was! :roll: :lol:
so I replied with 'tried another' ie another 5 elks :D , and then they replied :
"hello
sorry again
could we resend for you with your next order together ?
thanks for your kindness
regards"
but, I don't need anymore order's, as now got about 30x2764, 30x27128, 30x27256 & 10x27512 erasable eproms (all for free \:D/ , & bucket loads more if needed, all work, written once, never used! )
Phill wrote:...they are more expensive, but in the end there will be less faffing about

yeah, but we brits love a bargain hunt, even if it takes 10+hours of swearing /faffing, and throwing stuff out windows 8)
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby duikkie » Tue May 10, 2016 3:48 am

i am not english so therefor i am not on the peny :)

not a eurocent to much for the zeeuw :)

yeah, but we brits love a bargain hunt, even if it takes 10+hours of swearing /faffing, and throwing stuff out windows 8)

we dutch are so different then those people on the other side of the river :lol:

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Fri May 13, 2016 8:44 pm

my two failed ones, now seem to be working perfectly fine :roll: :P

maybe my elk plus1 cart wobbled ever so slightly, & gave bad verify errs, or wanted to go to sleep after 50mins :-k 8)

so Mr HQC chips are fine :mrgreen:
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Tue Jun 07, 2016 8:41 pm

wondered what was in the post today :? , HQC sent me another 5 not just the 2 'fail' replacements (that turned out fine for some bizzarre reason)
anyways, not tried them yet, but will report if fail later, or ok if not.
PS for sale £10 each inc pp :lol:
PPS must of been a busy week 13 yr 15....
Pics :
Attachments
13392121_10153869303212730_195789865355475111_o.jpeg
13392235_10153869303572730_8572222920462136894_o.jpeg
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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby Prime » Tue Jun 07, 2016 11:32 pm

CMcDougall wrote:PS for sale £10 each inc pp :lol:


I think not :)

http://uk.farnell.com/atmel/at28c256-15pu/parallel-eeprom-256kbit-dip-28/dp/1095782

Almost 2x the price of new ones.......

Cheers.

Phill.

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Re: Suspect ATMEL AT28C256 marked EEPROMs

Postby CMcDougall » Thu Jun 16, 2016 8:41 pm

^offer is off :lol:
me wrote:HQC sent me another 5 not just the 2 'fail' replacements

now I know why, the first 5 ARE duff's, they keep there data for <2weeks :roll:
the newer batch of 5 I got are still good :D
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