On Oct 16, 11:41 am, "SX-88" wrote:
I am in the process of recapping one of my receivers that uses many 0.05 MFD
paper caps. Since 0.05s are not READILY available, I am split equally on the
following:

1. Do I recap using the more readily available 0.047
MFD caps even though they are of less capacity
than the original? OR...

2. Do I recap by paralleling readily available
0.022 and 0.033 for a total capacity of
0.055 MFD?

If I do the 0.047 replacement I am violating the
rule I have had beaten in to me about NEVER allow a capacitor to be of LESS
capacity...but when they are
higher it is OK. However 0.047 MF is only 0.003 MFD
off the target 0.05 MFD value whereas the "safer" higher parallel
combination (0.055 MFD) is 0.005 MFD higher than the target capacity.

Thoughts? My receiver uses a lot of the 0.05s so it is not like I only
have one or two to consider.

Thanks for any help.

Gary


One more thought Gary,
You can look at the application and determine what the purpose of the
capacitor is, the approximate frequency, and the Xc of the capacitor
at that frequency. For instance, it it is in the IF amplifier stage,
you know that the frequency is 455KHz, and can calculate Xc. From
that, you can determine what range of values makes sense to replace
into the radio.
That said, remember that those paper capacitors had values given at
+/-20% tolerance. So why do you have a rule beat into you that you
never replace a capacitor with a value less than the original?
I just re-capped a Hallicrafters S-53A. The paper capacitors are ALL
rated at 600V. However, many of them are in low voltage applications,
and never see more that 30 volts accross them. Why put in a HUGE paper
capacitor? Because it was cheaper for the company to stock just one
part type and use it wherever a .01uF capacitor was needed.
So it is OK to question why a given component is where it is, and make
a judgement call on what would be a good replacement.
Also, as I replace the paper capacitors, I like to wear gloves. The
wax is kind of nasty to get on you.
Have fun, and good luck,
Gary