[time-nuts] Odd FTS 4060 Behavior - Update

Adrian rfnuts at arcor.de
Thu Jun 17 11:06:28 EDT 2010


Thanks to your assistance that inspired me to to take the 1000B OCXO 
apart, the FTS 4060 is now living happily in my frequency/time rack.
Call this a good day!

Adrian

Stanley Reynolds schrieb:
> 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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>>      
>
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