Audio amp replacement filter caps ???

[Joe]

I am replacing the filter caps in a Soundcraftsman A5002 power
amplifier. I can not find exact duplicate parts, but I can get close.

One is 11000 MFD 75VDC I cn find 12000 @ 100VDC to repalce it.

The other is 22000 MFD @ 30VDC, I can find 22000, or 23000 at about
45VDC.

Am I right in thinking that the higher voltage is not high enough to
matter, and the greater capacitance is OK too.

Joe massimj @ Hotmail Dot Com

 

[LASERandDVDfan]

The caps should work just fine, especially as we are only talking about very
little differences in capacities relative to filter caps. Capacitors,
especially filtering caps (or condensor caps depending on where you are from),
will typically have an actual capacity that is -/+ 20% off the indicated value.


Voltage ratings, on the other hand, indicate tolerance. Using a higher voltage
cap will only mean that the cap will withstand greater voltages than the
original lower voltage cap that was used in your equipment under normal
conditions.

You only have to worry about getting the same capacity cap if you are dealing
with a coupling cap or a frequency modifier cap. You can still go with a
higher voltage cap in this case provided that the capacity remains the same. -
Reinhart

 

[Asimov]

"Joe" bravely wrote to "All" (24 Jan 04 16:32:14)
--- on the heady topic of "Audio amp replacement filter caps ???"

Jo> From: massimj@hotmail.com (Joe)
Jo> Subject: Audio amp replacement filter caps ???
Jo> Organization: http://groups.google.com
Jo> Xref: aeinews sci.electronics.repair:18689

Jo> I am replacing the filter caps in a Soundcraftsman A5002 power
Jo> amplifier. I can not find exact duplicate parts, but I can get close.

Jo> One is 11000 MFD 75VDC I cn find 12000 @ 100VDC to repalce it.

Jo> The other is 22000 MFD @ 30VDC, I can find 22000, or 23000 at about
Jo> 45VDC.

Jo> Am I right in thinking that the higher voltage is not high enough to
Jo> matter, and the greater capacitance is OK too.

A slightly greater capacitance is just fine and sometimes one can even
get by with slightly less too, within reason of course. For example
one problem substituting a much larger capacitor is the rectifier peak
current may be surpassed, roughly speaking since I=CV/t.

The larger voltage however can be a problem in some cases because
higher voltage electros tend to be both physically bigger and have
greater internal resistance because of the thicker layers. However the
increased resistance may not be too significant in many applications.

The other problem with a larger voltage rating used at lower voltage
is it will lose the original voltage rating over time and may leak
slightly more than originally but this is typically negligible.

In summary for the capacitor values you specify I'd say "go for it".

.... I worked hard to attach the electrodes to it.

 

[Joe]

Ok, I did a test on the one suspect cap after testing A/C leakage on a
live circuit. Three of the caps had 15 to 29 mv, but one had approx 6
V on it. That was certain to be heard in the amp output. So to prove
it, I took two 4700MFD at 47VDC caps and tied them in series accross
the bad cap. Bingo, very quiet amp.

My problem is that the cap measures 2 inches diameter, 3 inches tall,
and is 22000 mfd at 35vdc good for 85C. Computer grade, with screws at
the top.

I have not found any that are good for the size. WHen I get a good
value on the electrical end, I can't fit it in the space that I have.
The way the caps are situated, I have no room to go bigger in any
direction.


2 D X 3 H min of 220000MFD at 35VDC Screw terminal at the top.

Anybody have a good source for a decent price on a cap like this?

Joe massimj @ hotmail dot com