Handy wiring guid B3-C3

Written by Daniel Virgin

It happens during the B3/C3 lifetime that upper and lower keyboards assembly have to
be pulled out from the cabinet and put on the workbench for several reasons such as :
 
- removing black caustic foam  
- replacement of contacts
- dendrites cleaning
- dead note,  
- open tapering leads,  
- and there are more...
 
Less frequently, similar problems may also appear at pedal keyboard.
In any case, all wirings from TWG (*) to keyboards have to be unsoldered.  
Inversely, same situation may be encountered if TWG has to be removed out from the
cabinet in case of coil pick-up replacement f.i. and the like.  
 
When remounting, there is absolutely no room for any wiring error. Since all cables  
are laced and black coloured, during re-soldering, it's sometimes confusing.  
 
Of course, indications are available in the service manual but to my opinion, such
information are not clear enough, printed in very small characters and it is not always
easy to find one's bearings.  
Most of the time, B3/C3 service manuals are copy of copy of copy ... so at the end it
becomes simply unreadable.  
 
Then, I have decided to investigate that specific matter and come up with a "handy
wiring guide" in order to facilitate that re-cabling operation without any possible wiring
mistake. That was the initial intention.  
 
The note position of keyboard is added at each terminal of TWG according to the
Hammond table III entitled " Frequency numbers assigned to keys and pedals " – refer
to Page 3-4 of the B3/C3 service manual.
 
For those who are equipped with frequency-meters or scopes with built-in frequency
counters, the frequency of each note has been also added at each TWG terminal.  
 
This article is mainly focused on correct 'Re-wiring' after maintenance intervention on
keyboards. Dismounting of keyboards are not covered in this article.  
(as an example, refer to  http://b3world.com/hammond-techinfo3.html - § 5-78).
 
An adequate technical expertise is compulsory. So this article is mostly addressed to
qualified technicians endowed with sufficient know-how, dexterity and ...  patience.

Download the complete article with pictures and diagrams here.