Ron -
Ripple current is a relatively new specification for electrolytic
capacitors, which today see much higher frequency ripple typical of
DC/DC converters (aka switching power supplies,). The result is that
that newer caps designed to have extremely low ESR, and so large ripple
currents are typical.
The heat generated by the current flowing through that low resistance is
a major determining factor of capacitor life. There are calculations to
determine the various contributors to capacitor heating in a given
scenario, but... From a practical standpoint, the RMS value of the
ripple is 0.707 X the peak AC voltage squared divided by the ESR of the
capacitor.
Bottom line... Pick capacitors that are a physical match to the ones in
the PS-7, rated at 105 degrees C if possible, and forget them for
another 30 years.
73, Garey - K4OAH
St Charles, IL
Drake 2-B, 4B& C-Line,& TR-4/C Service Supplement CDs
<www.k4oah.com>
Ron wrote:
Okay before everyone says Heathkit shop like they did last time, note that the
PS7 is the 13.8 volt power supply for the TR7 not the L7 power supply. I need
new filter caps, any thoughts on where and which ones?
I spotted some on mouser, but I can not find their ripple current ratings.
Apparently Mallory has changed numbers slightly and all I can do is guess given
the size above and below that they are about the correct current rating. On
that subject, I presume the ones in the supply are at least 12 amps each. That
would get them close for the 25 Amp constant current that the supply is suppose
to be able to run. With the fan cooling them, I would think 12 amp caps would
be about right.
TNX es 73,
Ron WD8SBB
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