Hello - I am recapping the amplifier in a circa 1982 Proton 300 Table Radio and am unable to find one cap - part 17-2.5SF405M, Electrolytic Bipolar 4uf 25V. The closest I have found are 3.3uf and 4.7uf. I do not know what function the cap is serving and do not know the ramifications of trying to find a work around. Surprised to not be able to find the appropriate part - wondering whether there is a generally accepted swap for some other size/type of capacitor? Please advise in layman terms. Much appreciated. Thank you.

 

How do you know it's bipolar?
You could likely use a 4μF ceramic capacitor or the 4.7μF you found.
The value is likely not critical and using a larger value should work without problem.

 

How do you know it's bipolar?
You could likely use a 4μF ceramic capacitor or the 4.7μF you found.
The value is likely not critical and using a larger value should work without problem.

Thank you for replying - the service manual identifies it as a Bipolar capacitor. It is an amplified speaker(two way) - if this is the only capacitor identified as bipolar, is it likely to be a speaker crossover capacitor? If this is the case, apparently changing the uf will change the crossover frequency. Do other types of capacitors(ceramic for example) offer the same frequency resistance function of electrolytic capacitors in a crossover application? Once again, thank you, and any further consideration you may happen to give this matter would be much appreciated.

 

The ceramic will likely have a tighter tolerance, and work at least as well, if not better than an electrolytic.

 

The ceramic will likely have a tighter tolerance, and work at least as well, if not better than an electrolytic.

I see upon closer examination of the manual that the capacitor in question is in the "Tweeter driving AMP" section of the board, as opposed to the "Crossover CKT" section. I will look into finding an equivalent sized ceramic capacitor if this remains your advised solution.

 

Additionally, found 4uf electrolytics (axial as opposed to radial) in the 150V range - would this be an option to replace the 25V original?

 

Additionally, found 4uf electrolytics (axial as opposed to radial) in the 150V range - would this be an option to replace the 25V original?

If they are bipolar, yes.