[NJARC] Capacitor question

[antqradio at juno.com]

Joe
Are you sure it is a mica cap and not paper?  Is the bad cap black in
color?  What are the approximate dimensions?  Flat or round body shape? 
Is one side of the capacitor connected to chassis ground?

Since the radio plays (AM&FM?) with the bad (split) capacitor, I would
guess it is a bypass and not a coupling cap.  I have replaced bypass (and
coupling caps for that mater) with either metal film or ceramic
capacitors with equal success.  Some people prefer one brand over another
but I haven't seen that it makes much difference.  

There is a caution with the hi Z ceramic capacitors since they change
value with temperature and applied voltage, sometimes drastically.  For
bypass and audio coupling, there isn't much of a concern.  Don't use them
in oscillators or frequency determining networks.  If in doubt, use film
capacitors with equal or higher voltage rating.

I just like the ceramics because they free up a lot of room under the
chassis and allow room for modern filter caps to replace those bad canned
electrolytics.

Let us know what you do and how it works out.

Regards,
Jim

On Sun, 20 Mar 2005 21:06:33 EST TrainBee at aol.com writes:
> Visit our web site - See http://www.njarc.org
> _______________________________________________
>         I have a Philco 52-944, AM-FM tabletop radio.  The radio is 
> in 
> excellent condition and will be a great addition to my collection.  
> The problem is 
> that there is a mica capacitor that is split in half at the seam (it 
> is one of 
> the rectangular types with the value printed).  It is a .047 at 400V. 
>        Now that you have that, can I use a tubular cap to replace 
> it, or 
> should I use one of the newer silver mica caps?  The radio plays, 
> but the caps 
> that are in there look like they melted down a while ago, so I plan 
> to play it 
> safe and replace them.  
>        
> 
> Any advise would help.
> Thanks,
> Joe Devonshire