[sdiy] Tantalums in general

[Sadpaul]

if tantalum is bad for power supplies why are they used in MFOS + -  
wall wart power supply?




On Jun 10, 2009, at 6:40 PM, George Hearn wrote:

> Sorry to put a spanner in the works on this thread but I do  
> disagree with
> some of what has been said.  Tantalum is a solid electrolyte device  
> and
> generally chosen over liquid electrolytes (Aluminium electrolytic  
> etc.) when
> reliability and long term stability is paramount.
> 	One good example is PC motherboards, good ones will advertise the
> use of solid capacitors, e.g. tantalum, as aluminium electrolytics  
> are prone
> to fail when subjected to the high temperatures often seen in  
> modern high
> clock rate systems.  Even if they do not fail their capacitance can  
> reduce
> dramatically.
> 	For long time constant circuits I guess tantalum might be quite good
> if you need a large capacitance but in my years I have never had to  
> use one
> for this application.  I would be interested to know what their DC
> performance is in terms of change of capacitance with applied DC  
> voltage...
> George
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of John Henson
> Sent: 11 June 2009 00:12
> To: synth-diy at dropmix.xs4all.nl; Gil W.
> Subject: Re: [sdiy] Tantalums in general
>
> Hi All,
> back in the days tantalum capacitors had (still have} two redeeming
> features...
> Low leakage and very low ESR.
> The former is self explanatory and the latter meant it could  
> decouple up to
> fairly high frequencies without a parallel mounted polyester or  
> ceramic.
> The end of the tantalum era came when the price of tantalum ore  
> skyrocketed
> following political instability in the worlds only source of  
> suitable ore
> (Zaire IIRC).
> Tantalum capacitors are even now horrendously expensive compared to  
> 'lytics.
> The loss of tantalum meant rapid research into electrolytes giving  
> us the
> low ESR 'lytics we enjoy today.
> If you have a synth, module, whatever, with tants decoupling the power
> rails, remove them and replace with low ESR 'lytics. It could save  
> a gig one
>
> day.
> Tants as the timing elements in envelope generators or LFO's are  
> fine, this
> is the application at which they excel.
> Regards
> John
> ----- Original Message -----
> From: "Gil W." <gil_we at yahoo.com>
> To: "Samppa Tolvanen" <samppa.tolvanen at gmail.com>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, June 10, 2009 9:05 PM
> Subject: Re: [sdiy] Tantalums in Yamaha CS20M/CS40M
>
>
>>
>> What was the reason they used tanatalums at all, back in the days ?
>> The writing on the circuit board, where the tantalum lay, shows the
>> positive mark rather than the negative one as like any other  
>> polarized
>> capacitor, meaning they planned dropping tantalums in there at the  
>> first
>> place.... Any particular reason ?
>>
>>
>>
>> --- On Wed, 6/10/09, Samppa Tolvanen <samppa.tolvanen at gmail.com>  
>> wrote:
>>
>>> From: Samppa Tolvanen <samppa.tolvanen at gmail.com>
>>> Subject: Re: [sdiy] Tantalums in Yamaha CS20M/CS40M
>>> To: "Gil W." <gil_we at yahoo.com>
>>> Cc: "synth-diy at dropmix.xs4all.nl" <synth-diy at dropmix.xs4all.nl>
>>> Date: Wednesday, June 10, 2009, 10:47 PM
>>> On Wed, Jun 10, 2009 at 9:52 PM, Gil
>>> W.<gil_we at yahoo.com>
>>> wrote:
>>>>
>>>> Particularly the power supply... There are four
>>> 1uf/35v tants in there, can I just drop 1uf electrolytes
>>> instead of them ?
>>>>
>>>
>>> I'd say it's more than safe. Electrolytics die, but
>>> Tantalums.are.prone to commit a messy suicide.
>>>
>>> Samppa
>>>
>>
>>
>>
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>>
>
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