On Mon, 31 Mar 1997 23:58:16 -0500 "Tom Rauch (W8JI)"
<W8JItom@worldnet.att.net> writes:
>>From the 1995 North American Capacitor Company catalog:
>The "ancient" CGS style 380 mfd used in Ameritron supplies has a
>ripple current rating of 3.3 amperes and an ESR of .212 ohms typical
(page
>78). A 390 MFD LX style has a ripple current rating of 2.2 amperes and
an
>ESR of .510 ohms (page 91).
>I didn't follow your point of why you want to use a capacitor with
>lower ripple current rating and more ESR in a capacitor input supply.
Did I
>miss something?
>
>73 Tom
I think you missed my whole point Tom.
A. The 381LX capacitor has more than adequate ratings for the average
commercially marketed ham amp. Plus, the ratings are for 105 degrees
C, not 85 as with the CGS. That higher temperature rating will more than
compensate for the ESR and in a real world amp supply it will not be
running anywhere near those ratings. Why take up extra weight and space
if you are already past the point of diminishing returns?
B. Why did MFJ/ Ameritron take such a cheap shot in their ad (April 97
QST, pg 14)
against modern capacitors. In the AL-811 no less! I could grant
them a point in the AL-1500 maybe, but not in that toy amp.
In case you forgot, this thread was started when someone mentioned
an ad knocking "short stubby " capacitors in their
competitors equipment.
C. I'll repeat myself....the CDE 381LX, from my experience, has better
production tolerances compared to the CGS permitting higher value
equalizing resistors. After all, was it not you Tom, who claimed at
the start of this subject that you had to use low value resistors?
All I am doing is challenging that assumption based upon the same
catalog data you have referenced.
You were correct about the resistors when used with randomly
selected CGS capacitors. That is the primary reason for the high
capacitor failure rate in Amp Supply amps; they used 100K 2W carbons
and poor tolerance CGS type capacitors. The voltages across the
string were anything but equal.
I'll stay tuned for your rebuttal which will likely sidestep the basic
issue....or we can stop now and go on to a different subject.
73...Carl KM1H
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