hammond A100 - drawbar stuck on (when turned off)

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joninc
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hammond A100 - drawbar stuck on (when turned off)

Post by joninc » Mon Sep 12, 2016 2:36 pm

yeah, it sucks. on the upper manual, right hand manual preset (Corresponds with B- far rightmost preset) - there's a 5th harmonic overtone getting through somehow when all the drawbars are turned off.

On the other manual preset (Bb) - it's fine.

On the lower manual (both setting) - it's fine.

Any ideas of how to fix or trouble shoot this issue. Just started in the past few weeks.

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analogika
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Post by analogika » Tue Sep 13, 2016 8:53 am

Does switching percussion on/off have any influence?

Usually, percussion is triggered off the topmost (1') drawbar, which is the sixth harmonic, I guess. When percussion is switched on, that drawbar's harmonic is killed.

I've heard of mods that restore the harmonic even when percussion is on, or that route it to a different drawbar in order to enable the octave overtone - maybe something shorted there?

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Nick Sevilla
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Post by Nick Sevilla » Wed Sep 14, 2016 9:18 am

This usually indicates a partial short in that circuit.

Thankfully, these are built like ancient cars, where it is easy to trace a problem on an individual button or drawbar.

As analogika stated, try switching on / off the percussion section, and se if that influences at all.

http://theatreorgans.com/hammond/faq/a-100/a-100.html

That has all the service manuals, plus some experts on all things Hammond. I am sure if you are patient, you can fix it yourself.
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joninc
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Post by joninc » Mon Sep 19, 2016 5:05 pm

thanks guys - it was related to the percussion. Instead of being set for a quick short burst at the start of the note it was set to wide open sustain!
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