29 Aug
2004
29 Aug
'04
9:39 a.m.
I have two identical 72pin memory SIMMS out of an HP workstation. One is
damaged by having a single 3pin SMD component physically destroyed, with
only the leads remaining. The second is complete and functional. The
damaged component's reference designation is CR5, so I am thinking it is
a rectifier and not a transistor. The black plastic SOT-23 package is
marked with 5A followed by a K rotated 90deg counter-clockwise.
Any suggestions on how to identify the part? Is there a pointer
somewhere to how SMD components are marked?
-chuck
29 Aug
29 Aug
9:51 a.m.
At 05:39 PM 8/29/2004, you wrote:
I have two identical 72pin memory SIMMS out of an HP
workstation. One is
damaged by having a single 3pin SMD component physically destroyed, with
only the leads remaining. The second is complete and functional. The
damaged component's reference designation is CR5, so I am thinking it is a
rectifier and not a transistor. The black plastic SOT-23 package is marked
with 5A followed by a K rotated 90deg counter-clockwise.
Any suggestions on how to identify the part? Is there a pointer somewhere
to how SMD components are marked?
K is the typical symbol for the cathode.
It might work very well without it if it was reverse bias protection.
But it might have been used as a constant voltage drop of Vf.
Ed
10:12 a.m.
> I have two identical 72pin memory SIMMS out of an
HP workstation.
> One is damaged by having a single 3pin SMD component physically
> destroyed, with only the leads remaining. The second is complete
> and functional. The damaged component's reference designation is
> CR5, so I am thinking it is a rectifier and not a transistor.
That would be my inclination too.
> The black plastic SOT-23 package is marked with 5A
followed by a K
> rotated 90deg counter-clockwise.
This says to me "five-amp rectifier pair", especially if the K is next
to the middle lead. This strikes me as somewhat unlikely on a 72-pin
memory module; I see no reason it would want a rectifier capable of
carrying five amps.
Do you have a scanner, or some other means of getting pictures of the
two modules? I'd be happier if I could see the markings myself (not
that I could necessarily say anything even if I did, of course).
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11:16 a.m.
> The black
plastic SOT-23 package is marked with 5A followed by a K
> rotated 90deg counter-clockwise.
This says to me "five-amp rectifier pair", especially if the K is next
11:43 a.m.
> The black plastic SOT-23 package is marked with 5A
followed by a K
> rotated 90deg counter-clockwise.
This says to me "five-amp rectifier
pair", especially if [...] More like the '5A' is a code for the diode
type.
That's one plausible other theory I have, too. A third is that the
device is something more like a voltage regulator and the CR
designation on the board does not indicate a rectifier, but instead,
perhaps, a parts-list code, or maybe refers to some other device, or
whatnot. Another reason to want pictures: to estimate how plausible
some of those theories are.
Can you figure out what it's connected to (do any
of the connections
go to supply lines or ground, for example).
Yet another reason I'd like to see pictures. Many memory modules
include solder pads for some large-size module; for a module of (say)
half that size, only some of the RAM chips are installed. Such modules
not infrequently include solder pads for what I might loosely call
jumpers, to indicate the module size. It would not surprise me if
that's what this device were - and if, for example, there are similar
pads nearby with nothing attached on either stick, that would reinforce
the theory.
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12:12 p.m.
In message <200408292351.TAA02231(a)Sparkle.Rodents.Montreal.QC.CA>
der Mouse <mouse(a)rodents.montreal.qc.ca> wrote:
So no-one saw the link I posted then?
It's listed as both a transistor (with a "CR" part designation, unlikely)
and
a rectifier diode - can't remember the specifics, but it was listed.
Later.
--
Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem(a)dsl.pipex.com | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.dsl.pipex.com/ | 48xCD, ARCINv6c IDE, SCSI
... "Bother", said Pooh, as he fell into the nitric acid bath
I don't know the SOT23 package. I do know I have
seen surface-mount
devices I would have no trouble believing capable of carrying five
amps. This is another reason I asked for pictures, if possible; if (as
I infer from your note) the SOT23 package is too small for it to
plausibly hold a five-amp device, that theory slips down the list.
A SOT23 is about the size of the body of a 1N914 or 1N4148 diode :)
More like the
'5A' is a code for the diode type.
That's one plausible other theory I have, too. A third is that the
device is something more like a voltage regulator and the CR
designation on the board does not indicate a rectifier, but instead,
perhaps, a parts-list code, or maybe refers to some other device, or
whatnot. Another reason to want pictures: to estimate how plausible
some of those theories are. 
12:51 p.m.
On Sun, 29 Aug 2004 19:43:07 -0400 (EDT)
der Mouse <mouse(a)rodents.montreal.qc.ca> wrote:
I don't know the SOT23 package. I do know I have seen surface-mount
devices I would have no trouble believing capable of carrying five
amps. This is another reason I asked for pictures, if possible; if
(as I infer from your note) the SOT23 package is too small for it to
plausibly hold a five-amp device, that theory slips down the list.
As I noted, though, I'd be surprised to see such a thing on a 72-pin
memory module. :-)
Perhaps he should use a DMM to carefully ohm out the part on the
non-damaged module. If it's a diode it will conduct only one way. If
it's a zero ohm shunt it will read as a short. Or it might be a
capacitor.
>> The black plastic SOT-23 package is marked
with 5A followed by a
K>>> rotated 90deg counter-clockwise.
This says to me "five-amp rectifier
pair", especially if [...]
Are you suggesting a 5A diode (or diode pair) in an
SOT23 package?
I would be _very_ suprised. More like the '5A' is a code for the
diode type.
That's one plausible other theory I have, too. A third is that the
device is something more like a voltage regulator and the CR
designation on the board does not indicate a rectifier, but instead,
perhaps, a parts-list code, or maybe refers to some other device, or
whatnot. Another reason to want pictures: to estimate how plausible
some of those theories are.
Can you figure out what it's connected to (do
any of the connections
go to supply lines or ground, for example).
Yet another reason I'd like to see pictures. Many memory modules
include solder pads for some large-size module; for a module of (say)
half that size, only some of the RAM chips are installed. Such
modules not infrequently include solder pads for what I might loosely
call jumpers, to indicate the module size. It would not surprise me
if that's what this device were - and if, for example, there are
similar pads nearby with nothing attached on either stick, that would
reinforce the theory.
10:13 a.m.
In message <41324D06.908(a)nktelco.net>
"Charles H. Dickman" <chd_1(a)nktelco.net> wrote:
Any suggestions on how to identify the part? Is there
a pointer
somewhere to how SMD components are marked?
Yee-upp - it's called the SMD Codebook:
<http://www.marsport.demon.co.uk/smd/mainframe.htm>
Add it to your bookmarks list - you never know when you might need it :)
Later.
--
Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem(a)dsl.pipex.com | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.dsl.pipex.com/ | 48xCD, ARCINv6c IDE, SCSI
... Television is so dull that children are doing their homework.
30 Aug
30 Aug
12:18 p.m.
Philip Pemberton wrote:
Yee-upp - it's called the SMD Codebook:
<http://www.marsport.demon.co.uk/smd/mainframe.htm>
I had seen this, and although it did include the 5A part, there was no
mention of a K lying on it's back. I was hoping somebody would say the
reclining K was used by "Diodes-Are-Us" and I could find a data sheet.
I probed the chip on the good board and it looks like pin 1 is connect
to SIMM pin 72 through a 1k resistor and pin 3 is connected to SIMM pin
42. Pin 2 seems to be connected to nothing. If I probe across the chip
from pin 1 to 3 I see a wierd negative resistance one
way and a positive
resistance the other. There is probably a capacitor somewhere
messing
with the meter.
I don't have any idea what the pinout is. I searched a bit, and pin 72
might be ground and pin 42 was either a data bit or a column address strobe.
I might tack a 1N914 between pads 1 and 3 and see what happens.
-chuck
7201
days inactive
7202
days old
8 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
chd_1＠nktelco.net -
mouse＠Rodents.Montreal.QC.CA -
philpem＠dsl.pipex.com -
Pres＠macro-inc.com -
sastevens＠earthlink.net