30 Sep
2007
30 Sep
'07
9:05 a.m.
Is there any kind of common failure mode for EPROMs? I've just had a couple
which are refusing to erase - I'm getting repeating patterns of bits which
refuse to clear (i.e. go high) under the eraser.
Normally they seem to erase in ten minutes, twenty at the most - these pair
have had 30 so far. Just wondering whether to keep baking 'em or just toss
them because they're junk...
(I've managed to find what I did with my nice eraser - but it'll still only
erase a couple of chips at once)
cheers
Jules
30 Sep
30 Sep
9:41 a.m.
Jules Richardson wrote:
Is there any kind of common failure mode for EPROMs?
I've just had a
couple which are refusing to erase - I'm getting repeating patterns of
bits which refuse to clear (i.e. go high) under the eraser.
Off the top of my head:
- Stuck address lines (a given address line has no effect on the output of
the EPROM)
- Stuck data outputs (a given data line is always low or always high)
- Failed memory cells (a given cell has the same value, even after repeated
erasing)
I'd be inclined to just dump them, with a spot of hammer-assisted destruction
first. At least the latter ensures they won't creep back into your parts bin
at some later date, ready to cause more trouble...
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10:57 a.m.
Philip Pemberton wrote:
Jules Richardson wrote:
Hmm, makes sense. One of the chips was all over the place; lots of 0xBF that
would never go to 0xFF and chunks of 0x80's all over the address range (didn't
look to be tied to a particular address line, though). The other chip was
jammed consistently at 0xF0, so looks like a simple data output failure.
Is there any kind of common failure mode for
EPROMs? I've just had a
couple which are refusing to erase - I'm getting repeating patterns of
bits which refuse to clear (i.e. go high) under the eraser.
Off the top of my head:
- Stuck address lines (a given address line has no effect on the
output of the EPROM)
- Stuck data outputs (a given data line is always low or always high)
- Failed memory cells (a given cell has the same value, even after
repeated erasing) I'd be inclined to just dump them, with a spot of
hammer-assisted
destruction first.
Done.
I just threw another couple of chips into the eraser and they're fine - I'm
just getting a bit low on 27128's these days. First time I've ever had any bad
ones, though...
cheers
Jules
11:18 a.m.
On 30 Sep 2007 at 18:57, Jules Richardson wrote:
> I'd be inclined to just dump them, with a
spot of hammer-assisted
> destruction first.
I'd try baking a couple first. If they're headed for the landfill
anyway, why not? It seems to me that you could occasionally bring
one back to life in the old days. Maybe a couple of hours at, say,
85C?
Cheers,
Chuck
12:11 p.m.
Date: Sun, 30 Sep 2007 17:05:09 +0100> From:
julesrichardsonuk at yahoo.co.uk> To: > Subject: EPROM deaths...> > > Is
there any kind of common failure mode for EPROMs? I've just had a couple > which
are refusing to erase - I'm getting repeating patterns of bits which > refuse to
clear (i.e. go high) under the eraser.> > Normally they seem to erase in ten
minutes, twenty at the most - these pair > have had 30 so far. Just wondering whether
to keep baking 'em or just toss > them because they're junk...> >
(I've managed to find what I did with my nice eraser - but it'll still only >
erase a couple of chips at once)> > cheers> > Jules> Hi
The most
common problem I've seen that
causes this is just poor contact with the
programmer.
Dwight
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6:41 p.m.
On Sunday 30 September 2007 12:05, Jules Richardson wrote:
Is there any kind of common failure mode for EPROMs?
I've just had a couple
which are refusing to erase - I'm getting repeating patterns of bits which
refuse to clear (i.e. go high) under the eraser.
Normally they seem to erase in ten minutes, twenty at the most - these pair
have had 30 so far. Just wondering whether to keep baking 'em or just toss
them because they're junk...
Sounds to me like what you're seeing isn't so much a problem with the memory
array in there as a problem with the output pin, likely shorted to ground...
I've encountered a few like that. Most likely caused by inserting or removing
them with power applied?
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