Burned DIMM pads

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JohnO

We put a bunch of computers into a large trade school, and we're getting
back DDR400 dimms with pins 184 and 181 burned off. We think these are being
hot-swapped, and we're going to run some tests in a couple days to see if we
can duplicate, but have any of you seen this before?

-John O
 
JohnO said:
We put a bunch of computers into a large trade school, and we're getting
back DDR400 dimms with pins 184 and 181 burned off. We think these are being
hot-swapped, and we're going to run some tests in a couple days to see if we
can duplicate, but have any of you seen this before?

-John O
Click to expand...

Not necessiarly deleberately hot swapped, but if you don't make sure
that BOTH of the retaining clips are in, the stick may be angled, and
if you're unlucky enough to have just the right (wrong) angle, you can
zap them. That's where I'd put my first test.

One of our newbie techs did that once. After that, we put a "no
smoking" sign on his cubicle. :) I don't recall which pins were shorted
but it WAS a perfectly good stick of PC133. But ther RAM stick was
painfully hot afterwards. It was tossed, we also tossed the motherboard
on general principals.
 
Not necessiarly deleberately hot swapped, but if you don't make sure
that BOTH of the retaining clips are in, the stick may be angled, and
if you're unlucky enough to have just the right (wrong) angle, you can
zap them. That's where I'd put my first test.

One of our newbie techs did that once. After that, we put a "no
smoking" sign on his cubicle. :) I don't recall which pins were shorted
but it WAS a perfectly good stick of PC133. But ther RAM stick was
painfully hot afterwards. It was tossed, we also tossed the motherboard
on general principals.
Click to expand...


Ahh, you're saying powered up but the stick isn't fully inserted?

-John O
 
JohnO said:
Ahh, you're saying powered up but the stick isn't fully inserted?

-John O
Click to expand...

Bingo.

It'll either:
a) Not work, and do no damage
b) smoke the ram and/or motherboard

Depending on luck, angles and motherboard design. You'll want to use
the same motherboards as your trad shcool or you may not be able to
reproduce.

The pins on ram sticks are straight, so when they're tilted, it's
possible to short across ajacent pins. Other shorts may be possible.
THe one that smoked the last one had the thing tilted at a 5-10 degree
angle.
 
You can tell if the memory stick is not fully and correctly inserted on most
motherboard as the retaining clips at each end of the memory stick will not
be in the fully upright position. Try removing a stick buy pushing back on
the clips and then re-inserting and you'll know what I mean.

JS
 
JS said:
You can tell if the memory stick is not fully and correctly inserted on
most motherboard as the retaining clips at each end of the memory stick
will not be in the fully upright position. Try removing a stick buy
pushing back on the clips and then re-inserting and you'll know what I
mean.
Click to expand...

The instructions to the students used to have good photos of that, and I'll
have to check if they are still there (on the road today, Iron City).

Good feedback guys, I appreciate it.

-John O
 
On Wed, 17 May 2006 11:05:29 -0400, "JohnO"
We put a bunch of computers into a large trade school, and we're getting
back DDR400 dimms with pins 184 and 181 burned off. We think these are being
hot-swapped, and we're going to run some tests in a couple days to see if we
can duplicate, but have any of you seen this before?
Click to expand...

Tip: ATX "off" is NOT OFF - there's still power applied to the mobo!

So you have to re-train users and techs who grew up with pre-ATX
systems that now they have to unplug from mains, rather than simply
switch off the PC case, before any open-case work.

Also, note that DIMMs may differ in operating voltage. Usually the
notches will be slightly offset so that you can't easily (say) plug in
a 3.3V SDRAM DIMM into a 5V SDRAM slot.

The second issue may be an issue if you have a mix of PCs that cross
generations (e.g. old 5V Socket 7 SDRAM vs. newer PII/PIII) and folks
try to redeploy RAM resources across the pool of PCs.

If it doesn't easily fit, there's a *reason* :-)

Do the burned DIMMs also have bruised or filed-open notches?


-------------------- ----- ---- --- -- - - - -
Click to expand...
Trsut me, I won't make a mistake!
 
If it doesn't easily fit, there's a *reason* :-)
Do the burned DIMMs also have bruised or filed-open notches?
Click to expand...

No, these are a *lots* of identical systems built to our specs, and students
are using our instructions for removing and then reinstalling the dimm.
Unfortunately, these systems don't have power supply switches, making the
removal of the power cable necessary--and I suspect not always accomplished.
We do tell the students to make sure the light on the mobo is off. Looks
like we have to stick a meter on those pins and see what's there when
off/AC-attached.

Of all those computers (~1k) we've had maybe ten burned dimms, so there's
nothing *completely* wrong with the instrux or hardware. Problem is, the
instructors don't know exactly what step was being performed when the smoke
appears, and the students won't cop to blowing the dimm if they did make a
mistake. Being under our warranty, the instructors don't really care
how/why, either. So I'm unlikely to get something like "it happened when I
did step 23", and we have to make some best guesses.

-John O
 
JohnO said:
No, these are a *lots* of identical systems built to our specs, and students
are using our instructions for removing and then reinstalling the dimm.
Unfortunately, these systems don't have power supply switches, making the
removal of the power cable necessary--and I suspect not always accomplished.
We do tell the students to make sure the light on the mobo is off. Looks
like we have to stick a meter on those pins and see what's there when
off/AC-attached.

Of all those computers (~1k) we've had maybe ten burned dimms, so there's
nothing *completely* wrong with the instrux or hardware. Problem is, the
instructors don't know exactly what step was being performed when the smoke
appears, and the students won't cop to blowing the dimm if they did make a
mistake. Being under our warranty, the instructors don't really care
how/why, either. So I'm unlikely to get something like "it happened when I
did step 23", and we have to make some best guesses.

-John O
Click to expand...

I think you're looking over one of the things the man said
he asked "Do the burned DIMMs also have bruised or filed-open notches?"

I've found that (by my lousy counting) when a DIMM gets burnt by
putting it in the wrong way, then ram contacts 85 and 77, - VDD and
VDDQ respectively, get burnt on the RAM chip. There were certainly a
distance of 8 between them - including one of them/'the first one'
..(85-77=8)

smoke comes from the socket on the mbrd , whilst certain contacts on
the ram get hit too. Those contacts on the RAM that get hit look burnt.
perhaps, looking 'filed down'. They look different anyway. As if the
metal has been filed fof and what was beneath the metal, the little
area of that contact, is burnt.
The RAM socket will also look more seriously messed up at the point of
those ram contacts.

Are you sure the sockets are burning and the ram modules are ok?

by the way, you may get more answers from
comp.sys.ibm.pc.hardware.chips
 
I think you're looking over one of the things the man said
he asked "Do the burned DIMMs also have bruised or filed-open notches?"
Click to expand...

These dimms have a notch that's about 1/4-inch off center. Backwards, the
notch is off by nearly a half inch. No way they go in backwards without
flopping around in the socket. The one I'm looking at has no bruise in the
right place.

Anyone ever hear of "Blitz" memory? The sticker, chips, and board all have
this name on them, and they don't exist on the web...we have a suspicion
that they might just be crap modules.

FWIW, our guys were playing this weekend and learned that a hot-swap works
fine. :-)

Are you sure the sockets are burning and the ram modules are ok?
Click to expand...

The dimms are obviously burned, pads at 184 and 181 are gone and the edge of
the module shows heat/smoke damage...a scratch & sniff smells like burned
pcb, too. Sockets show pins melted into the plastic.

by the way, you may get more answers from comp.sys.ibm.pc.hardware.chips
Click to expand...

Thanks, if we need to pursue this further I'll check it out.

-John O
 
JohnO said:
These dimms have a notch that's about 1/4-inch off center. Backwards, the
notch is off by nearly a half inch. No way they go in backwards without
flopping around in the socket. The one I'm looking at has no bruise in the
right place.

Anyone ever hear of "Blitz" memory? The sticker, chips, and board all have
this name on them, and they don't exist on the web...we have a suspicion
that they might just be crap modules.
Click to expand...

Maybe rebranded, if you put them in a windows machine, install everest
or aida32, you might get the information stored within the ram chip.
FWIW, our guys were playing this weekend and learned that a hot-swap works
fine. :-)
Click to expand...

You mean you got away with it? No damage? Well, you can get away with a
lot of really bad practices, a lot more than people generally think.

Ps: is this hot swap as in powered off, but there's a little juice
going through the circuits, or hot swap as in fully booted? There's a
huge difference.... One is relatively safe, the other, well...
 
You mean you got away with it? No damage? Well, you can get away with a
lot of really bad practices, a lot more than people generally think.

Ps: is this hot swap as in powered off, but there's a little juice
going through the circuits, or hot swap as in fully booted? There's a
huge difference.... One is relatively safe, the other, well...
Click to expand...

Power on, system running at the Win XP desktop, remove the dimm. Put it back
in. Windows crashes, of course, but the hardware is fine. Amazing. For all
we know the mobo or dimm could die in a month, but they are working fine
right now.

-John O
 
JS said:
How warm do they feel when the PC has been on and active for a while?
Click to expand...

The guy who did it is putting out a major fire at the moment, I'll ask him
later. If he has time, I'll have him measure it.

-John O
 
Manufactures of Memory Sticks don't always use the same manufacturer of the
actual memory chips or if they do the LOT Number may be different. If the
stick feels cool to the touch then take one stick out and see who made the
chips. There should be a name and or part number. See if this matches with
the chips on the burned out memory sticks.

JS
 
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