[HAM] CV mods

[Gary]

Thanks Magnus for the lesson! So the percussion sound is "borrowed" from
harmonics taken from drawbars 4 and 5. And the processing is done thru
the tablet switches, and the preamp. I assume the AO-29 handles this
process in the same was as the AO-28. I guess I will start by cleaning
up the AO-29 making sure that it works! I think I threw out the tablet
block from the M3, so I will have to hunt for one with all the
components..... Thanks again Gary 

-----Original Message-----
From: hammond-bounces at zeni.net [mailto:hammond-bounces at zeni.net] On
Behalf Of Magnus Enorson
Sent: Sunday, April 01, 2007 5:29 PM
To: 'The Hammond Forum'
Subject: Re: [HAM] CV mods

>Hey Guys, I just downloaded the AO 29 schematic. I see the percussion
>amp portion but I don't see or understand how the percussion sound is
>generated. As I have said, I am not a tech, and do appreciate you guys
>and your help. Gary

At the percussion switch assy, signal is taken from drawbars 4 and 5.
The
switches determine which one of the two signals is to be sent on to the
preamp by means of the percussion harmonic selector switch. Say that 3rd
harmonic percussion is selected and perc is switched on - in this case,
signal meant for drawbar 5 instead gets sent along to the preamp
terminal H.
At terminal J, this same signal comes back out and is returned to the
drawbar so that drawbar 5 still plays normally, even though its signal
is
being "percussed" as well.

Meanwhile, at terminal K, the preamp is waiting for a sign that it's
time to
do some percussing. This is done by routing signal from a drawbar
(usually
number 9) to terminal K - this is also taken care of by the percussion
switch assy. When an upper manual key is played, the preamp sees this
event
as "drawbar 9 just got grounded" - and responds by allowing the signal
at
terminal H (the signal to be "percussed") to flow for a short period of
time. This is what is perceived as "percussion" tone - what really
happens
is that a gate opens to let signal thru, then it closes at once.

Then there are 2 more terminals - L and M - which have to do with
percussion
volume, and percussion decay rates. 

There are lots of connections, resistors and other things to consider if
you
construct your own switch assy - but if you get an M-3 switch block, all
that is solved. Guess what route I recommend? :)

/Magnus
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