[time-nuts] GC-1000 Clock Cap Choice?

[Brooke Clarke]

Hi Didier:

I know CMAX had a real problem with their LF time receiver boards.  The 
high value caps used to resonate the loop-stick antenna permanently 
changed value so much when heated to soldering temperature they no 
longer worked.  Now they use radial lead caps shrink wrapped to the 
loop-sticks instead of having the cap on the receiver PCB.

Have Fun,

Brooke Clarke
http://www.PRC68.com


shalimr9 at gmail.com wrote:
> Also they are almost impossible to solder by hand without setting high internal stress which sometimes results in cracks, not necessarily immediately. Even on professional wave solder equipment, high delayed failure rates are not uncommon, which sometimes results in many units having to be recalled. Don't ask me how I know, I was lucky this was not my design, but it could have been.
>
> Yet, I still use them, under the assurance that our manufacturing folks have resolved the problem, which for now seems true.
>
> Didier
>
> Sent from my Verizon Wireless BlackBerry
>
> -----Original Message-----
> From: Chuck Harris<cfharris at erols.com>
> Sender: time-nuts-bounces at febo.com
> Date: Sun, 16 Jan 2011 17:43:18
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] GC-1000 Clock Cap Choice?
>
> I have found that such high dielectric constant capacitors have other
> problems in some circuits.  While the capacitance value is dropping,
> as much as 50% when you apply voltage, their physical volume is
> changing.  They behave as piezoelectric transducers.
>
> I have used them inappropriately, and found them singing loudly.  If
> that were to happen in a switching regulator, I would think the ultrasonic
> vibrations could do damage to the capacitor, the PCB, or the solder joints.
>
> -Chuck Harris
>
> Poul-Henning Kamp wrote:
>    
>> In message<4D336A19.40709 at freenet.de>, "Dr. Frank Stellmach" writes:
>>
>>      
>>> High cap value Ceramics are available since years, [...]
>>>        
>> Can you clarify one thing for me: When I studied datasheets for these
>> it looked like they drop 50% of their capacitance at a DC voltage
>> of 10-20V.
>>
>> Doesn't that make them a so-so bargain for power supply bulk capacitance ?
>>
>>      
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