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Hammond: Percussion Too Soft
Old 30th June 2009
Gear Addict
rodreb's Avatar

Hammond: Percussion Too Soft

The percussion on my 1963 Hammond A100 is too soft. It's definately there but just not as pronounced as it should be. Does anyone know if this could be caused by a weak tube? Or what exactly might cause this?

Any advice would be appreciated.

Old 30th June 2009
Lives for gear
Scinx's Avatar

This may help:
The Organ Forum - Just became the caretaker of a '59 A-100 (question on key percussion).

And if not, I'd recommend posting your question, or searching around, at if no one around here knows.

Old 30th June 2009
Lives for gear
BOWIE's Avatar
Weak tubes will definitely kill the attack. Power tubes are usually the first to go.
If it happens at any volume, the preamp tubes are probably weak. If it gets significantly worse as you increace the output, then it's probably the power tubes. Could easily be both. One of the big tricks in buying a tube organ is to find one with good tubes because re-tubing can sometimes cost more than the organ is worth.
Old 30th June 2009
Gear Maniac
corworld's Avatar

There is a 12au7 that you need to check. Not sure which one (schemo not in front of me) Once you swap that tube and eliminate it as a possibility, check the percussion cutoff adjustment pot in the organ.

I assume you know the quirks of percussion - top manual only, normal vs. soft switch, B or Bb preset keys only.

If you are really wild, try an 12at7 instead, It will take your head off.
Old 30th June 2009
Lives for gear
Kris's Avatar
I had a similar issue and my buddy who is an organ expert used a 9 volt battery to clean some contacts in the organ... It could be this simple fix, but I didn't do it myself so I can't quite explain how to do it here...
Old 30th June 2009
Gear Addict
rodreb's Avatar

Thanks everyone! Some great suggestions here. I'll be checking the tubes and replacing any that show up weak or bad.
I am familiar with the flashing routine but to me, that's kind of a last resort, kinda scary.
Yes, I am familiar with the quirks of Hammond percussion. I also have a 1947 CV that's had percussion added, and a 1962 M3, and I USED to have a B3 that I bought brand new in 1964 that I wish I never would have gotten rid of.
Thanks again for all the great responses.
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