Motorola SH21

Quick question concerning acceptable replacement capacitor size. The crossover cap. in the left and right channels is a 5mf 25V non-polarized cap. Since a replacement cap. of the same size does not seem possible, it looks like the closest sizes are 4.7mf or 6.8mf. If these sizes are acceptable, which one is preferred? Or would it be better to connect a 2.2 and 3.3 in parallel for 5.5mf? Should you always use something larger than the original size?

Thanks for your help.

For a crossover cap, the value must be as close to the original as possible. It must also be nonpolarized. I saw some 1 uF mylar capacitors at a radio supply store. Connect 5 of these in parallel.

Record-changer,

Thanks for your response. One look on this forum and it is obvious that you are very invaluable to this forum. Your help is truly appreciated.

Upon looking at my original post, I noticed that I forgot to mention that the 5mf 25V non-polarized cap is electrolytic. Will the Mylar as you have suggested still work as a replacement or does that change your response?

I think I read somewhere that Tantalum may be a replacement for electrolytic?

Again, thanks for your help

That capacitor actually has two 10 uF 25 volt electrolytic capacitors in it, connected back to back to make it nonpolarized. This was done because, at the time, there were no non-electrolytic capacitors big enough to do the job. We have made some advances since then.

There is one difference in using the mylar caps: They will last longer. But make sure they can take 25 volts.

I understand what you are saying. Is there a limit to how high the voltage of the replacement cap. can/should be? Since the spec. is 25v, is using a 400v or 630v cap. okay?

If the cap is not electrolytic, go as high as you want. You are just paying more for voltage you don't need. But I doubt you will find a non-electrolytic with that high a voltage in the 5 uF range.

Don't go too far away from the working voltage with electrolytic capacitors. An electrolytic capacitor that is run far below its design working voltage will "reform" itself to a higher capacity and a lower voltage. This will change the crossover frequency.

Note that a polarize electrolytic will NOT work here, unless you have two back-to-back.

Thanks for your help. While replacing caps I have run across a resistor that is suppose to be 1k 2watt 10%. It is measuring 1197 ohms. Is this far enough out of spec. that I should replace it? If so, it looks like metal film resistors are the only thing I am seeing in the 2watt range?

It's enough out of range, considering the cheap cost of a replacement. Metal film is better.