Percussion problem with Hammond C-3

[hoopgroove]

I recently rebuilt a 1956 Hammond C-3. This included removal of the manual, new felt stops, bus bars, drawbar assembly rebuild, percussion and vibrato switches cleaned. It is now back together and starts and runs. I have a peculiar problem with the percussion. First of all the percussion does not seem to work. But oddly there is a constant whistle associated with the 8th and 9th drawbar. That is pull the 8th drawbar out and the tone increases, it never decays, the actual note is high B. Similar with the 9th drawbar, a constant whistle that increases in volume when the drawbar is pulled out. The tone for this one is a high C. This true for both B and Bb presets. Turning the percussion switch OFF stops the 9th drawbar whistle when using the B preset. That does not happen with the Bb preset. The whistle is always there.

Is this a pre-amp issue? Or could the problem be in the switches?. The percussion volume control has no effect on this. Note, I did not rebuild the preamp but this problem was not present prior to the rebuild of the manuals.

Hoping I can get some ideas or reference to a previous thread.

thanks,

[gtojimmy]

How did the organ work before all of the work? Did percussion work?

I'm hardly one to give advice, but I've recently gone through refurb of an A102, preamp, power amp, and some other work. After I was done, I started having a host of problems, most intermittent, and I finally decided to swap the tubes. Fired it up and no change!! About now I'm sharpening my axe, and decided to pull the preamp back out, and when taking the covers off the 110v terminals, I noticed one of the yellow leads which supplies power to the pilot light, and also supplies the heater circuits had one strand of wire (kind of like a wild eyebrow) poking out, and was contacting the cover! So, I started the organ with the cover off and problem gone !
In hindsight I had noticed that the pilot light seemed very dim, and when I probed it with the vom it would go out, but just thought just a dirty bulb socket! Had I chased that down earlier I would have found the issue sooner!
I should have triple checked my work and had better lighting! Of course if the organ was DOA, that's a different story...

[Jaim]

Strange - problem only on the upper manual / drawbars? I would start with the easy stuff. Check the ground wires from the DB's and manuals. The manual should have a ground wire which is connected via a screw on the cover.
Check the preset panel - all connections tight? No wire strands shorting 2 DB's together?

Jim

[tpappano]

I have no experience with sort of thing (yet) but since it involves two specific tones, might there be mis-aligned contacts on two of the keys? Perhaps from working on the bus bars?

[David Anderson]

One of my first principles of diagnostics is: When looking for causes of trouble, always look carefully at any repair work done after the organ left the factory.

You write: "this problem was not present prior to the rebuild of the manuals."

That means that somewhere in the process of the work you did, you made a mistake.

I have had to go behind people and correct their wiring/reassembly mistakes on a number of occasions, and the thing about tasks like that is that it's never something I could have predicted before I found the mistake, so it's going to be pretty difficult for any of us to figure out exactly what you did wrong. There are too many variables that make it different from diagnosing a stock circuit that's misbehaving.

I recommended taking a break, clearing your head, reviewing the wiring diagrams, and going back over the work you did.

[enor]

Do you perhaps mean that turning perc ON (not off) takes away the whistle on drawbar #9? If so, your problems are consistant with a misaligned busbar. (well two - the ones corresponding to the 8th and the 9th drawbars). When you re-inserted them after cleaning, a key contact on each bar ended up on the wrong side of the busbar.

[gtojimmy]

One of my first principles of diagnostics is: When looking for causes of trouble, always look carefully at any repair work done after the organ left the factory.

You write: "this problem was not present prior to the rebuild of the manuals."

That means that somewhere in the process of the work you did, you made a mistake.

I recommended taking a break, clearing your head, reviewing the wiring diagrams, and going back over the work you did.

Great Advice !

[hoopgroove]

Clarification of the issue. Top manual only. with the B preset. PERC OFF - whistles on the 8th and 9th drawbars. PERC ON - whistle on the 8th but not the 9th (weird)

Bb preset - Perc OFF, whistles on 8 and 9; Perc ON; whistles on 8 and 9.

And confirming the problem was not present prior to the rebuild.

Busbar misalignment makes some sense to me. Still uncertain about my next steps on this one.

[enor]

Next step: pull busbars again, and refit them. This time on the correct side of the two switches ;)

[enor]

Clarification of the issue. Top manual only. with the B preset. PERC OFF - whistles on the 8th and 9th drawbars. PERC ON - whistle on the 8th but not the 9th (weird)

Not weird. The 9th drawbar takes on the role as percussion trigger when you switch perc on, and goes away from the normal voicing. This is also why your percussion isn't working; because the contact is sticking it's in a permanent state of "key down" so it doesn't recharge. You should be able to hear just one "ping" as you flip the perc switch on though, but then no further pings.