Hello all,
Just got my hands on the drawbar and switch assembly off of a Hammond H112 on ebay
http://feedback.ebay.ie/ws/eBayISAPI.dll?ViewFeedback&userid=noble_mutt&item=280006089649&iid=280006089649&frm=1883&ssPageName=STRK:MEWN:SID
I had never seen the drawbar assembley before off of a Hammond, and have read all the threads regarding their midification. The problem is most of the threads drew no conclusion or solution. Is their anyone about who can tell me whether I go either:
a- Scan Matrix, although I’m not sure if that end of the programming is fully complete
b- the ‘resistive’ route using increments of 1.2k resitors over all eight bus bars to a max of 10k, and set up that bridge every eight drawbars
c- The DIN route.
Any comments would be greatle appreciated.
MP
link doesnt work.. shows me the feedback an ebay member
50 bucks! Score!!
At a guess, I’d go with the ‘resistive’ route using AINs, just because it means less programming needed, and less IO used… But I’ve never seen the circuitry so I don’t know how hard it would be to do…
That was my main thought. It would also require less circuitry. And then, when I hear you say it stryd_one, I know it is right… 
arent these drawbars able to be set halfway..that would mean 1 ain for every drawbar..
I thought the drawbars had a few steps on each one? I just had a look at the pic to see if my memory serves and it looks like 8 stops each to me…
Hey henry once you take delivery, could you take a bunch of pics for us? Especially closeups of mechanics and circuitry and such… That would be really helpful.
Anyway, better to use one AIN for each, than one DIN and a stack of DOUTs, or a stack of DINs… Although I noticed that the wiring is still there, so it might be easier to solder a scan matrix.
Hey henry don’t put tooo much weight in what I say… I’m still learning Don’t be fooled by my post count, that doesn’t mean that I know stuff, it means that I talk too much 
I took delivery yesterday ;D ;D
Will post a few photos. Yes it is eight stops per drawbar- switch style, not potentiometer. Each stop in in a series of stops is fed by the same current. It is also split in two. So from above, it looks like a matrix of 8 by 22 switches. If I am not mistaken a scan matrix would require soldering a diode at each point. Iwant to do as little damage to the original piece as possible. So I was thinking of feeding each of the eight point, or stops, on the drawbars with the relative currnent of a 10k slide pot. Ie resistor of 1.2k at stop one, 2.4 at stop 2 etc.
I have seen somewhere on the web (http://www.geocities.com/JDPetkov/Hardware/B4ce/B4ce.htm, here in fact. It was a discussion around here a while back that put me onto him) that the correct wiring was 8 by 1.2 resistors in parallel. This is wrong. I think he made his assumpyions before seeing the unit. He assumed that as the drawbar was pulled out, contact made with previous stops was maintained, and that resistors in parallel would achieve a result. (This is a common misconception of Hamond drawbars)
Will get the Nokia busy and take some snaps.
FYI This also arrived yesterday-http://cgi.ebay.ie/ws/eBayISAPI.dll?ViewItem&ih=004&item=140005371147&rd=1&sspagename=STRK%3AMEWN%3AIT&rd=1
;D ;D
Next thing you’ll be dancing around singing like Barry White “My darling, I… Can’t get enough of drawbars baaaby”
Mmmm. Could you post an mp3 of that?!.. :-X
You don’t know of barry white? 
You gotta hear this guy man, his voice is like pure molten gold
I know barry white- he saved my life!!!
I want the mp3 of you singing the drawbar song. Maybe we could choreograph a dance too. Could take off…
You heard it here first.
;D
Skinny white guy does barry white…hmmmm… I won’t embarass myself
Not when you put it like that, no. That sounds like something that should belong on a porn site… 
That’s it, I’m changing my sig ;D
OK No point taking photos as the unit is well sealed. I did a diagram though. The red lines with the red boxes indicate drawbars- just in case you were wondering, or being otherwise distracted by Barry White. The cross lines are where the contact busses run. I represents five drawbars, however they run for twenty two, The resistors in the diagram are my idea to midify it. I left out that the signal back to the DIN runs from the drawbar. I propose to break up the busses every eight drawbars and run a set of resistors again. Would this be necessary do you think, as Iwant to leave the unit as much as in tact as possible.
ADDENDUM: I drew in the contact point, but note that only on bus has contact with a bar at any given time!!!
I’m a bit confused… I see the buss that runs to ground, and a lot of other busses running in parralel…
Does it work so that each bar contacts the ground always, and one of the other busses depending on it’s position? or does it contact the ground always, and then each of the busses following?
So if the bar is set to ‘7’ (drawbar slides out 2 ‘notches’ from fully closed), does it contact only the 2nd buss, or does it contact buss 2 and buss 1?
Thats where confusion has arisen before. The drawbar touches only one bus at any given time. The drawbar is in fact a large one pole 9 way switch, break before make, to put it into modern context.
See you kept the sig
Mark
That might make it a bit easier
One thing about the resistive method that just occurred to me… The resistance of the buss itself will need to be taken into account… This might mean soldering the resistors onto each switch, rather than just the beginning of each buss. I’ll leave that up to your multimeter, I doubt it will be much, so you probably can ignore it.
Hah no I just changed it
