Wicon Capacitor replacement

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Keri Posted: Fri, Feb 19 2021 12:06 AM

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Hello

This thread is for suggestions and methods discovered for replacing the obsolete Wicon capacitors in many B&O models.  

Wicon capacitors tend to be differently sized than modern equivalents, and sometimes have odd terminal arrangements, such as a 3rd "blank" terminal for physical support.  Also, many B&O products have specially designed mounting arrangements specific for these now-obsolete capacitors.

Here's some methods I used when rebuilding a Beocenter 7700.  In particular, the 7700 has 3 identically sized Wicon capacitors in a plastic holder that screws down and securely holds the large capacitors down. 

I could have tossed the bracket and just soldered modern, much smaller capacitors to the board and it probably would have worked fine.   At the time, I didn't have a 3D printer, so here's some things I came up with....

Method #1 -  Glue modern capacitors inside of appropriately-sized pieces of copper tubing.   This method works quite well, actually. 

The copper tubing fits the brackets nicely.

Method #2 -  Restuff the Wicon capacitor.   Fortunately, these particular Wicon caps have a core that can be extracted , and is about the size of a modern replacement.  As the contact rivets are aluminum and cannot be soldered, I drilled holes in the two "live" terminals, and soldered the modern cap's leads to the original terminals.  Kapton tape holds the can together.  A modern cap of the same 4700uf/35v rating is shown for reference... there is an identical one inside the Wicon.  Note the 3rd "blank" terminal for physical support.

Method #3 - Find a modern capacitor of identical dimensions and adapt the terminals.

In this case, I used somewhat larger capacitors of the next higher voltage rating.  These capacitors are for the main +/- 30V power supply so a little extra capacity won't hurt.  In particular, the Wicons were 6000uf/35v and the replacements 6800uf/50v.  The replacement capacitor terminals are "snap-in" style, are too short and in the "wrong" places.  Some solid wire meant for house wiring worked well here. The wire is crimped over the terminal and soldered, then bent to the position of the original Wicon, then the excess clipped off.

And here we are, all happy. This arrangement has been in regular service for a few years now without issue.  After this picture was taken, the rest of the electrolytics were replaced along with the main power relay and both bridge rectifiers.  In particular, I feel that it is critical to replace all of the electrolytics in the STANDBY power system, and in the case of the 7700, the main power relay and the standby bridge rectifier as all are energized 24/7.