About opening cases, I opened one, repaired the oscillator and sealed it
back up (sort of).
In the early 2000's I had a 10 MHz OCXO that I used as the main
reference for my 10 GHz ham rover rig. It was really doing the job for
me until I accidentally hooked it up to DC power backwards and killed
it. I was hoping I could find some way to fix it. The oscillator was one
of the larger metal packages about 3" long by about 2" square. Here's
how I opened it.
Earlier I had tried to unsolder a smaller oscillator (about the size of
the MTI 260) with a torch. It's hard to heat the two sections fast with
a torch to melt the solder and find a way to grab them both ad pull
apart while the solder is melted. On that attempt, I eventually got it
apart but desoldered some internal circuit board components in the process.
For this other broken oscillator that I liked, I decided it might be
better to mechanically cut it apart. I assumed that the bottom piece
probably had a lip about 1/4 to 3/8 " long that fit tightly inside of
the top case and that lip was soldered to join the two pieces. I wanted
to cut off the top case right where the solder joint ended. I first
drilled a small test hole into the side of the outer case about where I
guessed the solder joint ended inside, Ideally just through the outer
case. Then with a small Dremel bit I enlarged this hole to to figure out
exactly where the solder seam ended. Then I carefully cut the main case
around the end of the solder joint. Ideally I cut just a little below
the end of the inner lip to keep a slight aligning surface for putting
it back together later.
For the cutting, I had a milling machine that I used, But once you know
where you want to cut, I think careful hack sawing or a Dremel ceramic
disk could have done the job. With only a little bit of solder now
holding the cut top case on, a little prying removed it.
[Another option might be to cut vertical slits in the outer case just
either side of the round corners (8 cuts) and just as long as the
internal soldered flange. The object is to turn the bottom sides of the
outer case into tabs that can be bent out. Driving a knife or chisel
into the solderd seam will hopefully pry the flaps outward. Getting the
corners loose would probably be the hard part. Cutting them as in my
other method might be the easiest. With this method, after opening, I
think you could then cut or melt of excess solder.off the main case and
base, straighten the main case sides and get a good strong seam on
reassembly.]
The blown oscillator I cut open had smt components inside. I replaced
all the active devices and electrolytic caps I found in the circuit and
checked to find that it worked again. (Yay!) I then was able to solder
the top case back on the base. Not quite as strong as the original with
just a narrow solder bead holding it, but working good as new.
Of course, if the oscillator's metal case is providing a hermetic seal,
you loose that, but most aren't, anyway.
So I just thought I'd mention this other mechanical attack method. I
think unsoldering the whole solder seal in one go and pulling it apart
without damaging the internals is a pretty difficult task.
-Rex
On 2/19/2016 9:09 AM, [email protected] wrote:
Alex,
I did not take opening pictures, but there is nothing to miss.
For the outside of the unopened case, there are plenty of pictures on eBay.
For the actual opening process, that consisted largely of scraping away solder
with a small, triangular file and utility knife until most of what I could
remove was gone and then using a hammer and screwdriver to separate the sides
from the bottom and then prying it off. Nothing pretty, and nothing much for
pictures. I used a tiny drill for my desoldering gun to remove an intial hole
in the solder for the adjustment hole. I then enlarged it with a 1/16th drill
bit (by hand). Ideally, a 2mm drill bit could be used. A 5/64th drill bit will
fit through the hole, but it is very tight. Probably not best to drill with
it because that would most likely enlarge the hole.
I wouldn't open it the same way again, but I'm not sure of the best procedure
that leaves the case and contents undamaged so that it can be reassembled. I
think, perhaps, that I would remove all of the solder that I could as before.
But then, I would make some sort of cut-out for the pins on the bottom and put
it in a pan on the stove and heat it up (hopefully, evenly) until the bottom
could be popped off. The outside case can get pretty hot without damage
because the only contact is the pins and the inside gets pretty hot when
running. The main risk is getting so hot that the plastic spacers on the pins
melt or the pin supports melt. I'm not sure how hot that would be. But, they
must have heated it fairly hot to melt the solder originally, so hopefully
that would work.
However, here are some pictures of the inside :) which is probably what you
want!
Top Case 1: [img]http://imgur.com/mvQkJ16[/img]
Top Case 2: [img]http://imgur.com/K7Rmeau[/img]
Bottom Case 1: [img]http://imgur.com/j7tC7QN[/img]
Bottom Case 2: [img]http://imgur.com/TKiofvi[/img]
Outer Oven 1: [img]http://imgur.com/bzYywj7[/img]
Outer Oven 2: [img]http://imgur.com/kKKynzc[/img]
Outer Oven 3: [img]http://imgur.com/xtzFsXD[/img]
Circuit Board: [img]http://imgur.com/PHgnVIm[/img]
Mike
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