Jeff Liebermann wrote in message
...
On Sat, 24 Oct 2009 07:58:34 +0100, "N_Cook"
wrote:
DVM resistance either way round is 6.2
It's blown. No way was that caused by package leakage or corrosion
which would result in an open circuit. What you have is an amorphous
blob of silicon. It's also a single junction, so my theory about
parallel diodes is all wrong. Sorry(tm).
Ant chance of Beryllium oxide or whatever the serious nasty is , likely
to
be inside?
Berylium oxide is white and is used as an insulator. It looks like a
hard ceramic. I looked at the data sheet but no insulator material
was specified. It's a DO-4 case, which methinks is just molded
plastic. If it's white ceramic, don't grind.
Which plane to go in with a dremmel cutting disc?
Circumscribe through the plastic near the metal base. It's a "cup"
which should come off easily. You may need to cut the solder eye off
the anode lead to remove the "cup". Sometimes, the guts is filled
with silicon grease.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
I've never done that before. Dremmelled around the top of the can exposing
plug of ceramic or glass which easily came away. As did the central copper
pin , presumably the joint to the die failed with the Dremmel vibration.
The casing is presumably steel , but no corrossion on the outsde. But on the
inside of the can is about 90 percent covered in brown deposit, presumably
rust. No grease or anything like that inside. Before dremmelling, the
reading had changed to 10 ohm and it still reads 10 ohm between stud and
weld blob on the die. I wil dig out my microscope but I doubt I'd see any
sign of crept silver, a few atoms thick, especially as it is presumably on
the edge of the die. I'd have to grind off the rest of the cap to view the
side of the die.
Certainly no obvious burn marks on the shiny sliver and no smoke/sputter
trails. As this failed in storage, or theoretically at the point of last
switch off , then no such damage expected.
Is ferric/ferrous oxide conductive? if some off that could magnetically
shift and migrate to the die.
Any other suggestions what/how to explore further ? eg fine needle point and
DVM going over the die surface plotting ohmage
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/