Hammond B3 / C3 Percussion zap quick fix

PLEASE READ: Here is a video demonstrating the procedure for ’zapping’ a Hammond C3 organ percussion.
The symptoms are a non-decaying, continuous percussion tone instead of a fully decaying tone.
The issue is commonly related to short circuits caused by zinc dendrites in the percussion switch assembly or the busbars (in particular the ninth 1 inch busbar).
Google for a more technical explanation of dendrites. Even NASA had this issue.

The idea here is to use low voltage DC to burn off (‘zap’) the zinc dendrite shorts and thereby get the percussion working again. It’s a quick fix and not really a long term solution. It does not always work, in which case further investigation in the pre-amp may be required. Best practice is to dissemble all relevant parts, clean and clear coat to prevent recurrence.

NOTE: I am not a qualified Hammond technician, this technique was explained to me online. Since it only applies low voltage (18 Volts DC) it is relatively safe. However, please note that even 18 volts can potentially cause damage to other components in the organ if you are not careful.

IMPORTANT: Note that the organ was unplugged from the mains for this procedure.

DISCLAIMER: There are potentially dangerous high voltage components present inside Hammond organs. DO NOT attempt this or any other repairs inside the organ unless you fully understand what you are doing. Call a professional tech if you don’t know, seriously! There may still be lethal voltages present even when the organ is unplugged.

The sound near the end is a little bit distorted. This is not an issue the organ, it sounds fine here. Problem is my phone's audio recording quality is pretty crap ;-)