Tone Generator Capacitor Replacement

The wax-and-paper caps used in the filter networks on the older ToneGenerators degrade with time (see CapacitorReplacement). In general, the capacitance of the wax-and-paper caps increases with age.

Undoubtedly, this strongly affects the tone of the organ.

Replacing TG caps will, correspondingly, drastically alter the sound of your organ.

Whether and how to replace the ToneGenerator capacitors is a hotly debated subject.

   Note: Around 1965 (I think) Hammond switched from wax-and-paper to mylar capacitors on their ToneGenerators.
   The mylar caps are much more stable.
   If your organ has mylar caps, you can probably safely bow out from this debate (and disregard the remainder of this page.

The Argument

Many people prefer (or have gotten used to) the mellower sound of aged capacitors. There are stories of tone generators which were "ruined" by capacitor replacement (the organs being saved only by the transplant of another tone generator (with original capacitors)). On the other hand, many swear by the brighter tone of a recapped tone generator. They argue that recapping restores the tone that was intended at the factory, and that, in any case, one can recover the mellow tone of the aged capacitors by pushing in the upper drawbars a bit.

Some claim that, should you decide to replace your tone generator capacitors, you really should individually match the value of each filter capacitor to it's filter coil (e.g. by using a capacitor substitution box and a spectrum analyzer to _peak_ the output of the tone generator.) They argue that this was what was done at the factory, and that to do otherwise will damage the balance between the levels of the various tones.

Others maintain that merely replacing the caps with caps of the correct nominal value will work fine.

What Kind of Capacitors?

There has been discussion on the lists about the type of capacitor used for recapping the TG. In addition, there have been claims that certain caps, chosen for their audio qualities should be used. Here is a link to a web page called The Sound of Capacitors - Capacitor Linearity. In it, experimental data is presented that provides a better clue of what to look for in a capacitor used for audio purposes.

FWIW, polypropylene "Orange Drops" have been recommended by one source who should know to be suitable replacements for TG filter caps.

User Stories

JohnMihevic has contributed this article on his (positive) experience with the Goff capacitor kit.

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