[time-nuts] Odd FTS 4060 Behavior

[EWKehren at aol.com]

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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