Dead percussion on B3/C3

Written by Daniel Virgin.

A lot of articles have been already written about unexpected 'dead percussion' on
Hammond B3/C3 and the way to get rid of this situation.
As owner of several organs, inevitably I was facing the problem.  
Here is what happens !
You start playing on your B3 or C3, select the Percussion tablet to 'ON' position and
nothing comes out. Totally dead percussion without any apparent reason.  
If you are on stage ready for a gig, you like the typical Jimmy Smith sound, your 'mood'
may change at once and you start to curse and swear.
As an old good Hammond folks, since you anticipate events, you are always used to
walk with a set of basic tools including "just in case" spare tubes. Then you start
replacing the three percussion tubes V5, V6 and V7, the last three tubes located at the
right side of the AO-28 preamp seen from the rear side. You know that since years.  
Still no percussion. Things become really shitty now. You are cursing a little bit more....
No other choice, the gig is going on and you start to simulate a kind of "soft
percussion" with the swell pedal, the best you can. What a torture to play like that
since with the next tune you have to take the lead on "A whiter shade of pale" of
Procol Harum where you need the Second Harmonic percussion.....That's reality.

The purpose of this article is to analyse 'in depth' the reason of such sudden failures
and provide several methods to prevent and fix this problem either temporarily or
definitively .
We all know that dead percussions can be caused by several components such as
defective caps around tubes V5, V6 and V7, faulty transformers T4, T5 and T6,
defective tubes, bad contacts at percussion tablets, broken wires, etc....and last but not
least by 'zincdendrites' or 'dendrites' for short.  
The common repairs of percussion function are not taken into consideration and this
article is mainly focused on the impact of these bloody dendrites formations which are
really a pain in the neck on those vintage Hammond's. 

Download the complete article with picure here.