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Replacing Amp Caps

I am currently trying to replace the caps in my Bedini 100/100 amp and I am having quite the time trying to find a replacement that will work. I am hoping that someone with more knowledge can give me direction on which way I can go. The amp recently stopped outputting a signal and after all the usual internal checks, with an amp as old as this, cap replacement should be on the list of things to do.

The values and associated numbers on the OEM caps are as follows:


National Cap

85DX

+22000MFD 65VDC

85C USA 8137

 

Screw Terminals

D=2.5"

H=4.0"

Apparently 65VDC caps are something in the distance pass, of the possible replacement values is either 63V or 70V
is there a rule of thumb of which direction this value can go? Since it is for an amp, is there a brand/style I should be looking at? I can find little to no information on National Cap, do I assume they are no longer in business and move to another brand?

I have been searching for five days and fully understand I am out of my element and looking for all the help I can getand open to all suggestions.


SteveA
stevea11757
stevea11757's avatar
stevea11757 OP
130 posts
 
https://www.mouser.com/ProductDetail/Nichicon/LNT1K223MSE?qs=%2Fha2pyFadujWNTRYoFZetWFsfOgqQfBavn9UCQaI2cVASAlZVSsWkg%3D%3D

At just 2000 hours for the Cornell-Dubilier getting the above with the higher max temp should extend its life considerably. Any advantage to the other that I am not aware of?

BTW- Mouser has just refunded a previous purchase of a different cap that I was going to use. But due to not reading the data sheet correctly I ended up with a smaller cap with a mounting stud. Emailed about a RMA and got a reply from Customer Service that told me not to bother and return and was crediting me the purchase price. Talk about customer service, will definitely be making the purchase there for the replacements.  
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cakyol's avatar
cakyol
940 posts
 
Here are the MOST important factors:

0- Do NOT skimp on price, buy the BEST if you want to use them forever (relative).

1- The higher the voltage the rating, the safer the bet. This also increases the ripple
current rating which makes it more resilient. This is VERY important for higher
power amps. It also protects for AC mains spikes which may occur and endanger
exceeding the voltage rating, even for a very short time, if you buy them right at the
limit voltage.

2 - Temperature, temperature & temperature. The higher the rating (105 degrees C) the
better the capacitor will be constructed and the longer it will last. Temperature is the greatest enemy of an electrolytic capacitor and higher ratings are much better.

Check these out, even tho they are obsolete, they can still be bought here & there. They last 20,000 hrs at 105 degrees C... almost unbeatable.

https://www.digikey.com/en/products/filter/aluminum-electrolytic-capacitors/58?s=N4IgjCBcoOwEwFYqgMZ...

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