Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next lowest
value or should I choose the closest value?
Thanks for your time,
Eddie

Edward R Morris wrote...

When I need to replace the mica caps and can't
find an exact replacement value should I choose
the next highest value or the next lowest value
or should I choose the closest value?

Since the small value caps are usually part of
some sort of compensation network I try to come
as close as possible.

BTW, I haven't forgotten about your request
Eddie, I'm just working my way down the
"stack" to you!

Jim McShane
Need Tubes? Got a H-K Citation (Pre) Amp?
Check http://pages.prodigy.net/jimmcshane
Repro knobs for Citation gear in stock!

Mica caps rarely fail and if they're in a frequency sensitive application
where they are commonly used you need the exact value or as close as
possible to minimize realignment.
73
Hank WD5JFR
"Edward R Morris" wrote in message
...
Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next
lowest
value or should I choose the closest value?
Thanks for your time,
Eddie

On Wed, 28 Apr 2004 14:01:35 +0000, Edward R Morris wrote:

Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next
lowest value or should I choose the closest value? Thanks for your time,
Eddie

Depends on what kind of circuit it's in, if it's in an
an oscillator or RF circuit or an audio equalization circuit
(like a phono preamp or FM de-emphasis), you want to stay
as close as possible. If necessary you can parallel values to get
what you want...sometimes there's no choice but to combine values,
if it's an odd value (like the 2750 pF part in a Dynaco PAS).

If it's something like a tone control in a 1948 Zenith
radio, well, in that case if you're in the ballpark,
you're OK...eg, if you need a 250 pF on the treble control and
all you have lying around is a 220 or 270 pf, those would be
close enough..

--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com

Edward R Morris wrote:

Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next lowest
value or should I choose the closest value?
Thanks for your time,
Eddie

+/-10% is the guide, and so a 250 pF should be replaced
by 270 pF, or 220 pF.
It depends where the cap occurs;
if its in a tone control the change in values probably
won't make the response any worse than it probably
already is even in the flat position.
That's what I have found with old tone control circuits.
They are usually way out, and different values entirely have to be
carefully chosen.
Caps in radio circuits might be critical, like the one in series with the
oscillator
tuning gang, which is often temperature compensated for drift, and a special
type,
but all the rest are arbitary values, able to be changed +/- 10%, unless they
are part of series or parallel tuning circuits, like in IF transformers.

Patrick Turner.

Edward R Morris wrote:

Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next lowest
value or should I choose the closest value?

Why do you want to replace them? I have never seen a bad mica cap yet...

Best regards,

Mikkel C. Simonsen

"Mikkel C. Simonsen" wrote in message
...
Edward R Morris wrote:

Hello. When I need to replace the mica caps and can't find an exact
replacement value should I choose the next highest value or the next
lowest
value or should I choose the closest value?

Why do you want to replace them? I have never seen a bad mica cap yet...

Best regards,

Mikkel C. Simonsen

I'm not the OP but...
I just had to replace a 39pf silver mica cap in my ARC SP-3's RIAA eq due to
it being microphonic!
That diagnosis took a while to figure out... ya know, they NEVER go bad you
see...

--
Alan Gallacher
Born to Tinker!