[time-nuts] Odd FTS 4060 Behavior - Update
Adrian
rfnuts at arcor.de
Thu Jun 17 15:06:28 UTC 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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