[time-nuts] Odd FTS 4060 Behavior
Stanley Reynolds
stanley_reynolds at yahoo.com
Mon Jun 14 18:21:52 UTC 2010
Pictures of 1000b dissembled here:
http://www.n4iqt.com/fts1000b/pictures/
Believe it is similar.
Stanley
----- Original Message ----
From: Adrian <rfnuts at arcor.de>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Mon, June 14, 2010 6:17:30 AM
Subject: Re: [time-nuts] Odd FTS 4060 Behavior
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
EWKehren at aol.com 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,
> rfnuts at arcor.de 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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>
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