23 Feb
2007
23 Feb
'07
7:42 p.m.
Recently, an accquaintaince was cleaning up his house
and came upon some old hardware, and asked - do I want
some old hard disks? Sure! He gave me a pair of old
Avid external 9 gig hard drives. Basically just 9 gig
5 1/4" FH Micropolis 50 pin SCSI drives in little-ish
external boxes. Perfect for some of these old boxen I
run around here. Anyway, I decided to hook them up
tonight. I cabled them up to an old PC, powered
everything on, and the SCSI card saw both disks. I
left the machine run while I went in the next room to
burn a Debian netinst CD. Five minutes later... what's
that smell? I went in the next room, now slightly hazy
and full of that acrid 'burnt electronics' smell. I
hit the switch on the power strip and started smelling
things looking for the source. Old 14" DigiView
monitor? - no... Old Compaq desktop PC? - no... Avid
external 9 gig SCSI hard drive? - <cough>.. yes
<gasp>.
I took the drive apart, expecting to find a burnt up
tantalum cap in the power supply or something -
nothing. Then I took the drive out (not easy, the
standoffs seem to like to stay with the screws rather
than the drive..), and flipped it over. There was a
burnt mark on the board the size of a nickel, and the
board had started to delaminate. In the center, a
charred husk of a something that resembled a surface
mount capacitor of some sort, a small rectangular
component about the size of a standard jumper laying
flat. Hmm, I haven't got anything to lose at this
point, so I picked the burnt thing off the board, it
had already unsoldered one side of itself, so I
wiggled the other side off, and removed the
surrounding debris. Morbid curiosity made me hook the
drive back up. Hmm, it spins... it comes ready... I
hooked it back up to the computer, and turned the
computer on, and lo and behold, the SCSI controller
sees the drive! I am currently running the Adaptec
SCSI controller's media test function on the drive
now, as I ponder why the Linux installer insists on
crashing on this particular box, but I really wonder a
couple things - what caused that capacitor to burn,
why does the disk still work, and how long will it
continue to work?
I imagine that the capacitor wasn't particularly
important, seeming as though the drive still runs, but
what baffles me is that even with sizeable damage to
the board, (it's bubbled up and delaminated in that
spot) the drive works. The capacitor was near three
voltage regulator type transistors on the board, so it
could have been a bypass type capacitor, and not
crucial to the circuit, but that doesn't explain why
it caught fire.
Computers never cease to amaze me.
-Ian
23 Feb
23 Feb
8:12 p.m.
From: Mr Ian Primus <ian_primus at yahoo.com>
---snip---
I imagine that the capacitor wasn't particularly
important, seeming as though the drive still runs, but
what baffles me is that even with sizeable damage to
the board, (it's bubbled up and delaminated in that
spot) the drive works. The capacitor was near three
voltage regulator type transistors on the board, so it
could have been a bypass type capacitor, and not
crucial to the circuit, but that doesn't explain why
it caught fire.
Computers never cease to amaze me.
-Ian
Hi Ian
That was a surface mount tantalum. The go up the same way
the tear drop ones do. They tend to do more damage because
they are surface mount.
If you are concerned, the value is most likely in the order of
10uf. It is surely a bypass cap.
Dwight
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8:51 p.m.
Mr Ian Primus wrote:
Recently, an accquaintaince was cleaning up his house
and came upon some old hardware, and asked - do I want
some old hard disks? Sure! He gave me a pair of old
Avid external 9 gig hard drives. Basically just 9 gig
5 1/4" FH Micropolis 50 pin SCSI drives in little-ish
external boxes. Perfect for some of these old boxen I
run around here. Anyway, I decided to hook them up
tonight. I cabled them up to an old PC, powered
everything on, and the SCSI card saw both disks. I
left the machine run while I went in the next room to
burn a Debian netinst CD. Five minutes later... what's
that smell? I went in the next room, now slightly hazy
and full of that acrid 'burnt electronics' smell. I
hit the switch on the power strip and started smelling
things looking for the source. Old 14" DigiView
monitor? - no... Old Compaq desktop PC? - no... Avid
external 9 gig SCSI hard drive? - <cough>.. yes
<gasp>.
...
Computers never cease to amaze me.
-Ian
If these are indeed 9G 5.25" FH Micropolis drives... run, run
very fast and far away from them.... (or better yet, throw them
as far as you can.... if possible... farther)... you will regret it
otherwise.
I've only had experience with one of those drives... that was
enough... and I've never touched another after I heard all the
horror stories.
The fact you have one or more that even seem to work is a
miracle (but your luck will run out).
It is too bad too... I liked Micropolis till that point. I especially
liked the old 5.25" FH 600M SCSI 'bricks'. They are reliable.
I've had a couple of 2G and 4G SCSI 3.5" Micropolis drives...
I have put much time on them... but they seem to work OK.
(I think the 4G is a Tomahawk... but I seem to recall hearing
bad stories about some (if not all) of those too).
My all time favorite for drives in the 9G and up catagory
(in 3.5 inch form factor) is quantum.... I've had a lot of those...
and I've only eve had one failure. And I probably accidentally
zapped it with static....
Now everything is pretty much Seagate, Western Digital, and
Hitachi.... I pretty much go with Seagate now.
-- Curt
24 Feb
24 Feb
3:47 p.m.
Recently, an accquaintaince was cleaning up his house
and came upon some old hardware, and asked - do I want
some old hard disks? Sure! He gave me a pair of old
Avid external 9 gig hard drives. Basically just 9 gig
I have a great oroblem regarding any 9GB hard disk as 'old'...
[...]
than the drive..), and flipped it over. There was a
burnt mark on the board the size of a nickel, and the
board had started to delaminate. In the center, a
charred husk of a something that resembled a surface
mount capacitor of some sort, a small rectangular
component about the size of a standard jumper laying
flat. Hmm, I haven't got anything to lose at this
[...]
I'll bet it was an SMD tantalum capacitor, and that it was a decoupling
(bypass) capacitor on one of the power lines. Such capacitors (both
wire-ended and SMD) are well-known for going short-circuit, and if
they're across a power line they generally catch fire (they glow red...)
and emit vast amounts of magixc smoke. And the device just carries on
working...
25 Feb
25 Feb
7:58 a.m.
Tony Duell wrote:
I'll bet it was an SMD tantalum capacitor, and
that it was a decoupling
(bypass) capacitor on one of the power lines. Such capacitors (both
wire-ended and SMD) are well-known for going short-circuit, and if
they're across a power line they generally catch fire (they glow red...)
and emit vast amounts of magixc smoke. And the device just carries on
working...
Just for a second possibility, *always* check the underside of "unknown"
drives before plugging them in (Which Ian may well have done) - because the
electronics are exposed, I've seen a few where there's been component damage
due to bad storage. It's possible (although I agree that a simple failure's
more likely) that something was shorted where it shouldn't be....
cheers
Jules
6514
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ard＠p850ug1.demon.co.uk -
dkelvey＠hotmail.com -
ian_primus＠yahoo.com -
julesrichardsonuk＠yahoo.co.uk -
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