Need to ID another SMD part...

D

Don Bruder

Guest
Still playing with the lightning-hit modem from the other day. Have
tracked traces to a component I can't ID, and am unable to get any kind
of useful meter reading from.

Physical:
Approx 6.5mm long, slightly less - perhaps 4.5-5mm wide, < 2.5mm thick.
Solid black body with silver/grey-ish markings. Two protruding tabs, one
on each short side, bent down to make contact with solder pads on PCB.

Drawing/markings:


| Approx |
| 6.5mm |
| |
| |
V V
-------- <------
| St | Approx
|| BHH || 4-5mm
| C638 |
-------- <------

Other (possibly) helpful commentary:
The "St" is obviously a logo (and maddeningly enough, one that I
recognize, but can't put a company name with) with the top of the "S"
joined with/forming the crossbar of the "t", all done in "inverse
video", if you follow my meaning. A notation silk-screened on the board
near it (may or may not be related to the part, but because of its
position, I think it probably is) reads "TVS1".

Anybody know what this "little black box" is? I can get no reading out
of it with my meter set for ohms, in any range, in either direction -
Meter behaves as if it isn't connected to anything. Whether this is
normal for this part (TVS1 = "Transient Voltage Suppressor #1", perhaps?
Sorta like a MOV?), or a symptom of it being fried is a complete unknown.

Google gives me nothing that makes any kind of sense on "C638" or "BHH",
and I expected (and got) too many hits to even TRY wading through on
"St", most dealing with - you guessed it - catholic saints, but none (of
the 6 pages or so worth of results that I bothered flipping through)
related to electronics.

Anyone?

And in the spirit of "teaching me to fish" instead of just giving me
one, if you know what this critter is, it would be appreciated if you'd
enlighten me as to how and/or where you found the information.


Thanks!

--
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>
 
-------- <------
| St | Approx
|| BHH || 4-5mm
| C638 |
-------- <------

Other (possibly) helpful commentary:
The "St" is obviously a logo (and maddeningly enough, one that I
ST Microelectronics (SGS-Thomson). www.st.com

position, I think it probably is) reads "TVS1".
You guessed it - Transient Voltage Suppressor. It should normally be
open-circuit, I believe.

Try googling for "SMD codebook" for help identifying the markings on
it. Yes, I could give you a URL, but I'm teaching you to fish, as per
request :)
 
In article <608b6569.0311141415.536dd87e@posting.google.com>,
larwe@larwe.com (Lewin A.R.W. Edwards) wrote:

-------- <------
| St | Approx
|| BHH || 4-5mm
| C638 |
-------- <------

Other (possibly) helpful commentary:
The "St" is obviously a logo (and maddeningly enough, one that I

ST Microelectronics (SGS-Thomson). www.st.com
Time for a heartfelt "D'OH!!!!"... I knew I recognized the logo. Just
couldn't dredge the name that went with it out of the rubble-filled
crater that is my memory!

position, I think it probably is) reads "TVS1".

You guessed it - Transient Voltage Suppressor. It should normally be
open-circuit, I believe.
Wow... MASSIVELY lucky guess! Also the only thing I could come up with
that made even a little bit of sense.

Try googling for "SMD codebook" for help identifying the markings on
it. Yes, I could give you a URL, but I'm teaching you to fish, as per
request :)
Smart-aleck! :)

Thanks a bunch. I'll check the st page and try to find this little
widget. Maybe it's supposed to be "open", maybe not... Need to find out
for sure before I continue chasing traces. It MIGHT be the
"deal-breaker" part that I need to fix. Or, there might still be more
trouble further "upstream"... That's the joy of lightning hits... You
never know WHAT might have cooked off.

--
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>
 
In article <_Zctb.6472$Wy2.91671@typhoon.sonic.net>,
Don Bruder <dakidd@sonic.net> wrote:
Time for a heartfelt "D'OH!!!!"... I knew I recognized the logo. Just
couldn't dredge the name that went with it out of the rubble-filled
crater that is my memory!

position, I think it probably is) reads "TVS1".

You guessed it - Transient Voltage Suppressor. It should normally be
open-circuit, I believe.

Wow... MASSIVELY lucky guess! Also the only thing I could come up with
that made even a little bit of sense.
A TVS is a Zener Diode rated for, ta da, supressing transients. There
are two types, one that's like a zener diode and another that's
bidirectional, looking like two zener diodes back to back. They have
their limits in terms of watts or joules that they can absorb. If one
took too big a hit, it would probably look open.

Mark Zenier mzenier@eskimo.com Washington State resident
 

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