[Heathkit] sb-200 capacitors (again)

[peter markavage]

Mike:
Part number was in Carl's e-mail, repeated below.
Pete, wa2cwa

Carl's e-mail:
"That would certainly not be my choice of capacitor for a HV doubler
supply. 
First of all the ripple spec is far from good, the load life is low and
the 
temperature rating is only 85C. Now for many hams the mantra is "Cheap Is

Best" but this is not the time to count pennies.
 
However I suggest the 105C Cornell Dublier 381LX series which is designed

for switching supplies and is a superb cap for amp use. Ive been using
that 
series since they came out for all my amp needs.
 
The Mouser # is 5985-450V150 @ $6.80 each in small quantities. Then
reduce 
the heat in the PS compartment by replacing the equalizer resistors with 
100K 5W MOX. Mouser # 286-100K @ .49 each.
 
The 330MF version of that cap fits perfectly in the SB220 plastic blocks
and 
noticably improves the regulation.
 
The amp you save may be your own."
 
Carl
KM1H
National Radio 1963-69
On Tue, 22 Nov 2005 12:24:55 -0500 "Michael Tortorella"
<w2iy at verizon.net> writes:
> I have been following the recent thread regarding 85C vs. 105C 
> electrolytics
> in the SB-200 supply.  I spent a good deal of my career at Bell Labs 
> in
> reliability engineering and I want to add that the voltage- and 
> heat-related
> failure mechanisms in electrolytic capacitors are quite well 
> understood
> (wish I could say that about other classes of components, but that's 
> a
> discussion for another day).  It is true that derating (i. e. using 
> the
> device at a lower power/temperature/voltage/current/whatever than it 
> is
> rated for) will, other things being equal, lengthen the comnponent's 
> life.
> In the SB-200 case, we should also consider the issue of duty cycle. 
>  Most
> of us don't have the amp on (i. e. transmitting) for 100% of the 
> time and
> even when it's transmitting, SSB and CW duty cycles are less than 
> 100%.  So,
> harking back to my days in undersea systems, to be conservative I'd 
> go with
> the 105C rated capacitors (and if I could get some with a higher 
> voltage
> rating I would use those too) but this is PROBABLY overly 
> conservative for
> typical amateur use (unless you use the amp on AM for hours every 
> day <g>).
> In any case, the cost difference is probably minimal, particularly 
> when
> compared with the annoyance of having to replace them yet again, so 
> I guess
> the bottom line is that the proverbial amateur frugality should be 
> judged in
> complete context (not just first cost!).
> 
> That said, can anyone point to a source for the 105C rated caps?
> 
> Again, no disrespect intended to Glen who has offered more help to 
> more
> people on this list than I can possibly remember.
> 
> 73 and happy T-day to everyone
> Mike, W2IY