la7sl Nils Petter wrote:
> Just a warning :
> Photoflash capacitors are not intended for PSU applications
>
Yup! They are intended in effect for no ripple. They are ramp charged to
a steady state from a high frequency supply that has very little current
capability. That's why the big ones may take 10 seconds to recharge from
a full discharge flash, whereas the big power supplies hit them a multi
amp charges of likely 20 amps or more, 120 times a second. Whole nuther
ball game. OTOH the new capacitors for the same job are much smaller
than those of 20 or 30 years ago.
73,
Roger (K8RI)
> They will generally not withstand the high ripple currents involved
> in a power supply under load conditions...
> Overheating and breakdown may be the result unless you run them
> very well below ratings..
> I do not think a commercial amp manufacturer will choose these in their
> product.
> BUT ... modern high voltage capacitors are definitely a lot smaller .
> Also the ones suitable for a PSU... But stay away from the "photoflash"
> types....
> The same goes for laser discharge caps and some medical equipment caps...
> Peter
>
> ----- Original Message -----
> From: "Edward Swynar" <gswynar@durham.net>
> To: "Charles Harpole" <k4vud@hotmail.com>; <amps@contesting.com>
> Sent: Monday, February 08, 2010 12:50 PM
> Subject: Re: [Amps] cap sizes
>
>
>
>> On 8th February, Charles wrote:
>>
>> "...I was surprised to see the small size of the same value caps .... the
>> originals in the DTR-2000 Dentron were 7 inches long and inch in dia. The
>> new ones (in 2009) were same size around, but about one inch and 1/3
>> long.... or short as the truth be told. Wow."
>>
>> ***********************************
>>
>> Hi Charles,
>>
>> Yes, the physical size of the new electrolytics really is quite
>> amazing...!
>> They pack a LOT of "ufd." in a VERY small can anymore---even at high
>> voltage.
>>
>> I believe the popular term for these things is/was "photoflash
>> capacitors".
>> I see them often at Hamfests in this area selling for as little as fifty
>> cents apiece! Needless-to-say, I always stock-up whenever I can...
>>
>> ~73~ de Eddy VE3CUI - VE3XZ
>>
>>
>>
>>
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>>
>>
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