Monday, April 06, 2009

Inside the Hammond L-100

After more playing and reading, I decided I really needed to get those drawbars working properly. There are numerous resources on the web with a wealth of information on Hammond tonewheel organs; this page describes what I did tonight.

Nearly all of the drawbars were really noisy when moved, and for a handful of them sound would drop out entirely on some settings. As I mentioned yesterday, the fundamental tone for the upper manual was one of these. It worked OK at lower settings, but from about 6 to 8 it would go silent unless I pushed down on the drawbar. Typically that drawbar contributes much of the tone of whatever my right hand is playing, and since my left hand is nearly useless, this was not a good situation.

So it was off to Radio Shack on my lunch hour to get some spray contact cleaner/lubricant, and tonight I opened up the organ once more.

It's a pretty complicated machine, and you can't even see the most complicated part of all, the guts of the tone generator.

Here's the back of the tone generator. Inside are dozens of gears and wheels and coils and magnets.

The spring reverb.

The synchronous motor, which is synchronized to 60 Hz AC power, and the reason these things never go out of tune. Note that it's attached to the tone generator via a spring; apparently the motor pulses a little, which would affect the sound in a bad, 60 Hz kind of way. The spring takes care of that. In some Hammonds, there's a second starter motor on the opposite end of the tone generator. Those models have two power switches that have to be turned on in a particular way; the L-100 just has the one.

Glowing vacuum tube goodness!

Here's the business end of the drawbars. I sprayed a little contact cleaner/lube in each of them, and worked the drawbars a little to clean them out. They work much, much better now. There's no noise or dropouts.

As far as I can tell, everything except the A flat pedal works now, though the mysterious "brilliance" tab doesn't seem to do a thing. I'm not sure what it's supposed to do; add brilliance, I guess. If you heard me play, you'd know that I could use a little brilliance.


Brendoon said...

Hi Joseph!
Kon Zissis has just released a large L100 mod document. I'd like to do it up as a free PDF download with pics etc.
Can I use parts of your pics in the text as decoration? I'm doing a big trawl for L100 players pics....

Email me too if you want a copy of the doc in Kon's current form.
hopefully this has included my gmail address, if not, reply on here and I'll come back with it.
Have a grand day!
-Brendon Wright

Joseph Thvedt said...


Feel free to use the photos. I'd be interested in seeing the document.

Brendoon said...

Thanks a ton, Joseph!
I'll credit you as joseph at this blog here, unless you have a preference. I think if you go to my profile here it'll have my gmail address. If you drop a quick email to me I'll fling the doc in its current state to you, and the pdf when its done. I've got a T500 and a C3, so my own pics are disqualified from the project!

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