Hammond B3 Percussion Effect

[KDakaWalt]

I know there are some Hammond B3 folks here. I have been asked by a friend to look at his B3. The percussion effect is weak. It seems to be there when you activate the switch but only momentarily. I plan to replace the tubes in that section first.

I searched and found references to “hair” that can grow on some leads in this section and cause a similar problem, but no specifics.

Any help and guidance is greatly appreciated. KD       

[GroundhogKen]

Start here:

http://www.dairiki.org/HammondWiki/PercussionTroubleshooting

Don't be in a hurry to do any zapping.

Schemes:
http://theatreorgans.com/hammond/faq/schematics.html


Ken

[topbrent]

Read over this so you can understand the AO-28 preamp:  http://www.bentonelectronics.com/AO28.html

Regarding zinc hair:  http://www.bentonelectronics.com/percussion.html

http://www.dairiki.org/HammondWiki/ZincDendrites

http://www.dairiki.org/HammondWiki/PercussionTroubleshooting

Check/replace the 12au7 tube associated with the percussion effect.

Since you are his repair guy now....read up on, and be prepared to rebuild the scanner someday.  
-   if it isn't giving the helicopter vibrato now......it will be someday.  They all do eventually.

[KDakaWalt]

Great info! Thanks so much.