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Hammond Aurora Classic drawbar problem

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  • Hammond Aurora Classic drawbar problem

    Dear All

    I acquired a Hammond Aurora Classic recently for my son, who studies classical organ but loves the classic Hammond sound and is quite enjoying playing it. It is in generally good working order, with - what I suppose are - the usual pops and crackles etc. of an old organ of its type.

    The main issue is that the drawbars for the upper manual don't work correctly. Each drawbar doesn't operate independently: i.e if you pull out just one drawbar and play a note, all drawbars appear to sound. The volume of these drawbars appear to work OK - i.e. the more you pull out any drawbar, the louder the sound becomes, but you can't hear the individual sound of each drawbar. (If you fiddle a bit with each drawbar, you can sometimes get each one to sound independently, but it's a fiddle and obviously not normal).

    I wonder if this is the reason: I took all 3 sets of drawbars apart for cleaning and reassembly and noticed that, whereas the other two sets have two copper (or bronze?) 'tabs' supporting the bars underneath at each side of the drawbar housing, these upper manual drawbars are missing one set of tabs - the set closest to the pull knobs. The missing tabs are basically u-shaped, fit into holes in the housing, and make contact with the underside of the drawbar as it slides back and forth. I thought initially that these tabs might just be for physical support of the drawbars, but do they make an electrical contact and could the absence of one set be the reason for this issue? Or is one set of tabs not there by design in the upper manual section?

    I'm not very skilled or knowledgeable about electronics, unfortunately, but any help you can give would be much appreciated.


  • #2
    I've got to the bottom of this problem now, I think. I noticed that this set of drawbars had what appeared to be a modification to them: someone in the past had soldered a short length of wire running from the ground wire contact on the PCB to the copper spring underneath the first (1') drawbar, and this in turn made a connection to all the other drawbars by way of a strip of metal placed along the edge of the drawbar housing underneath the copper springs to all the other drawbars. I think this had the effect of shorting the incoming electrical signal to all the drawbars to ground, rendering them redundant. I disconnected this wire and the drawbars seem to be working again. I don't know much about these organs, so perhaps I'm wrong and this wire is there by design for some reason, but it certainly stopped the drawbars from working properly. Can anyone shed any light on it?