Can blown RAM be detected by eye?

L

Luke A. Guest

Guest
Hi,

I have some DIMM's here and some of the chips on them look slightly
different to the others, kind of dull on part of the surface.

Basically, I just wanted to know if it is possible to tell if the chips
are blown by looking at them?

Thanks,
Luke.
 
Depends on how long the short circuit current flowed for and how hot the IC
became if it went with a big short. Other faults will not show at all for a
visual inspection.

Although "eyeballing a fault" is a common practice and solves many problems
with electronics, it does have it's limitations and more test techniques are
needed to further isolate the problem.

Hope this helps,
Peter
 
In article <pan.2003.09.17.08.24.53.145996@abyss2-nospam.demon.co.uk>,
"Luke A. Guest" <laguest@abyss2-nospam.demon.co.uk> wrote:

Hi,

I have some DIMM's here and some of the chips on them look slightly
different to the others, kind of dull on part of the surface.

Basically, I just wanted to know if it is possible to tell if the chips
are blown by looking at them?

Thanks,
Luke.
Click to expand...
Unless it's *SEVERELY* blown (tops blasted off chips, cracked chips,
scorched, charred, that sort of thing) probably not.

--
Don Bruder - dakidd@sonic.net <--- Preferred Email - SpamAssassinated.
Hate SPAM? See <http://www.spamassassin.org> for some seriously great info.
I will choose a path that's clear: I will choose Free Will! - N. Peart
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"Luke A. Guest" wrote ...
I have some DIMM's here and some of the chips on them look slightly
different to the others, kind of dull on part of the surface.

Basically, I just wanted to know if it is possible to tell if the chips
are blown by looking at them?
Click to expand...
Differences in surface finish could be entirely due to moulding
machine die/plastic variations. Not a reliable indicator.

OTOH, if you actually observe the smoke escaping...! :)
 
Unless it's *SEVERELY* blown (tops blasted off chips, cracked chips,
scorched, charred, that sort of thing) probably not.
Click to expand...
Well, I don't know really...I'm trying to go through a load of RAM on a
bunch of machines (which haven't been too reliable so far - well one has)
and one one DIMM two of the chips have a dull surface rather than shiny
(so you can see the text in the light).

I think that these are knackered, but again I need to test them some more
to make sure.

Thanks all,
Luke.
 
In article <pan.2003.09.17.19.26.02.128189@abyss2-nospam.demon.co.uk>,
"Luke A. Guest" <laguest@abyss2-nospam.demon.co.uk> wrote:

Unless it's *SEVERELY* blown (tops blasted off chips, cracked chips,
scorched, charred, that sort of thing) probably not.

Well, I don't know really...I'm trying to go through a load of RAM on a
bunch of machines (which haven't been too reliable so far - well one has)
and one one DIMM two of the chips have a dull surface rather than shiny
(so you can see the text in the light).
Click to expand...
Surface finish appearance is absolutely meaningless. The mold release
compound may have "bubbled" some as the casting was made, there may have
been dust in the mold, variations in the formula, pigment, or even
temperature of the plastic used for the case, how quickly/slowly the
chips were cooled after the molding process, or any of about 14
bajillion other things may be responsible for mind-bogglingly huge
visible finish variations, with none of them having any impact
whatsoever on the functionality (or lack thereof) of the chip. Short of
chips being blasted open, cracked, or charred (and even *THOSE* aren't
100% reliable, although they are a good indicator that the chip is
probably hosed) there simply is no reliable visual indicator of a chip's
functionality.

I think that these are knackered, but again I need to test them some more
to make sure.
Click to expand...
Electrical testing is the only way to be certain. Visual inspection of
the (electrically inert) plastic or ceramic shell of a chip CANNOT be
relied on as a diagnostic of the health of whatever circuit is on the
actual (electrically active) silicon wafer inside the chip. As an
indicator that the chip *MIGHT* be gone? Perhaps it can offer a clue. As
a definitive, or even slightly clueful, diagnostic? No possible way
unless you're looking at a chip that's literally blasted apart, and even
then, you can't be certain until proper electrical testing of the
circuit on the wafer is performed. Anything else is purest voodoo.

--
Don Bruder - dakidd@sonic.net <--- Preferred Email - SpamAssassinated.
Hate SPAM? See <http://www.spamassassin.org> for some seriously great info.
I will choose a path that's clear: I will choose Free Will! - N. Peart
Fly trap info pages: <http://www.sonic.net/~dakidd/Horses/FlyTrap/index.html>
 
"Bushy" (please@reply.to.group) writes:
Depends on how long the short circuit current flowed for and how hot the IC
became if it went with a big short. Other faults will not show at all for a
visual inspection.

Although "eyeballing a fault" is a common practice and solves many problems
with electronics, it does have it's limitations and more test techniques are
needed to further isolate the problem.

Hope this helps,
Peter
Click to expand...
I once found a faulty RAM in an Atari 520ST by touch. The particular IC
was quite noticeably hot, compared to the rest of the RAM, so it seemed
fairly likely to be the problem. I can't remember if there was some
reason I suspected the RAM in the first place, though I must admit
it was easier to find replacement RAM than some of the dedicated ICs,
so perhaps I paid attention to RAM because it was something I could repalce.

I don't know about the state of DIMM manufacturing, but in 1996 I bought
some 1meg 30pin SIMMs, and had a problem with one or more of them. It
looked like some of the pins hadn't been soldered properly so I used
my heat gun to reflow the solder. They worked fine for years after
that.

It's odd how I paid $40 for those four SIMMs (and felt I'd got a deal
considering I paid $80 for 64K of RAM in 1984), and just two weeks ago
I paid $40 for a 128meg DIMM (and if the rebate comes in, it will
be only $20).

Michael
 
On Wed, 17 Sep 2003 09:24:53 +0100, "Luke A. Guest"
<laguest@abyss2-nospam.demon.co.uk> Gave us:

Hi,

I have some DIMM's here and some of the chips on them look slightly
different to the others, kind of dull on part of the surface.

Basically, I just wanted to know if it is possible to tell if the chips
are blown by looking at them?

Thanks,
Luke.
Click to expand...
Some run hot, some do not. Blowouts are not usually visible as the
power levels inside these sticks is not all that great.

Best bet is to take them to a PC store. Most of them have Memory
stick testers. Or call around till you find one that does. They'll
surely test them for free in the hopes of making a sale.
 
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vmgnjdl5t763c3@corp.supernews.com...

OTOH, if you actually observe the smoke escaping...! :)
Click to expand...
Yes, It's never a good idea to let the smoke escape.
 
"CWatters" <colin.watters@pandora.be> wrote in message
news:kRgab.26261$Rw5.1501309@phobos.telenet-ops.be...
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vmgnjdl5t763c3@corp.supernews.com...

OTOH, if you actually observe the smoke escaping...! :)

Yes, It's never a good idea to let the smoke escape.
Click to expand...
Of course, at work we detect bad RAM cells by eye.
But it frequently takes $50M worth of test equipment,
and electron microscopes to make images that we
can detect by eye. :)
 
On Thu, 18 Sep 2003 11:41:04 GMT, "CWatters"
<colin.watters@pandora.be> Gave us:

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vmgnjdl5t763c3@corp.supernews.com...

OTOH, if you actually observe the smoke escaping...! :)

Yes, It's never a good idea to let the smoke escape.
Click to expand...

It's not safe to watch ever either. Unless you are behind a slab of
Lexan.
 
Luke A. Guest wrote:

Hi,

I have some DIMM's here and some of the chips on them look slightly
different to the others, kind of dull on part of the surface.

Basically, I just wanted to know if it is possible to tell if the chips
are blown by looking at them?

Thanks,
Luke.
Click to expand...
Not really. There are some exceptional cases where a defect makes a chip
blow up and look accordingly. Some older chips did sometimes overheat which
is also a means of testing, but nowadays you won't see anything on a
electrically damaged or defective chip. Try programmatically testing them,
there are some memory-testing programs available. Make sure however, that
the CPU and chipset used for testing the RAM is reliable.
 
Yup. The old Finger Test can sometimes find a catastrophic failure.

NOTE1: Lick your finger first and get off the chip quickly.
If you don't have the manufacturer's logo branded into your fingertip,
you can go back for a longer, more definitive test.

The voice of experience on burned fingertips here.


Note2: This only finds really bad ones--it can't guarantee any are good.
 
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