Bert,
I was surprised how easy oven disassembly was.
Remove the 4 (8?) screws that hold the connector plate and pull it out.
Take 3 layers of rubber foam out.
Gently pull on the flex board to pull the oven out of the dewar (avoid
pulling on the tiny coaxial cable).
The dewar may come out of the outer box when you're pulling. It's just
wrapped with a layer of foam. I held mine back to keep it inside.
Don't worry about pulling a bit stronger if required, the oven assy will
start sliding out of the dewar.
When the assy is out, carefully remove the brittle hard foam shell.
Remove the heater transistor screws.
Unsolder the temperature sensor flex wires from the bottom PCB (mine
looked like they were just sticked in the PCB contacts, but were
actually soldered in).
Gently pull the oven out of the PCB connector.
Pull both PCB's out of the oven at the same time. They might stick a
little because there is some silicone rubber on the opposite edge.
Adrian
[email protected] schrieb:
Adrian,
you did actually broke it down to the inside oven level. Is there any thing
to look out for. I have a FTS 1200 that has a problem 2 Hz off but I have
been reluctant to open it up. Any advice?
Thanks Bert
In a message dated 6/14/2010 6:02:38 A.M. Eastern Daylight Time,
[email protected] writes:
Only the turned edge connector pins of the two PCB's inside the oven
appear to have that problem.
I looked under a good microscope, and the female contacts as well as the
trimmer cap, both gold plated, looked good.
Now 12 hours later, the 4060 is still running fine with no alarm light
on and no signs of instability.
Adrian
Magnus Danielson schrieb:
On 06/14/2010 05:45 AM, Glenn Little WB4UIV wrote:
This is known as gold embrittlement.
The gold has to be removed before a good solder connection is made.
To remove the gold, tin the gold plated area.
Desolder the tinning.
Retin and remove the solder three times.
This should remove the gold which forms an amalgam with the solder.
After the gold has been removed, a reliable solder connection can be
made.
This is a common failure mode of radio power amplifiers.
If you can undo the connection without adding heat, you will see a black
area between the gold plating and the solder.
I do not know why the manufacturers insist on gold plating leads that
are designed to be soldered.
Silver plating seems like a better solution.
In this case, it appears that pins were soldered that were not designed
to be soldered.
Glad that you found the problem.
Removing gold is the simple option, it just take time and effort to
perform.
Gold and tin can under certain mixture relations from a gold-tin alloy
which is brittle, this is the problem. When soldering, gold dissolves
up into the tin blob very easily, that's why the above procedure work,
and also why it can become a real problem. However, this is not an
issue of the gold-tin relationship is sufficiently low on gold. When
soldering BGA on gold-plated PCB, the amount of tin in the ball is
given, but sufficiently thin gold plating is safe.
We had this problem in a time when the PCB maker didn't have proper
control, but once they got that the issue disappeared. There is a huge
difference between brittle and proper solder joints.
We still use gold on out board, and it works. We don't get any returns
due to that failure mode. So, gold isn't that bad, but you need to be
careful and aware. I have many old instruments (Tek, HP) that uses
gold-plated boards among other things. None of them has failed due to
that problem. Good that you localized that issue with the FTS1200 as I
believe more people have that issue with them.
Cheers,
Magnus
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