[time-nuts] Odd FTS 4060 Behavior

[EWKehren at aol.com]

Thank you Adrian
I did print out the instructions and one quiet day I will go for it. Thanks 
 again
Bert
 
 
In a message dated 6/14/2010 7:17:58 A.M. Eastern Daylight Time,  
rfnuts at arcor.de writes:

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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