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

[paul swed]

Good tidbit on the cmax

On Thu, Jan 20, 2011 at 10:29 AM, Brooke Clarke <brooke at pacific.net> wrote:

> 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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>>
>
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