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A-100 Percussion issue, Leslie motor issue, and any techs in Vancouver BC?

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  • A-100 Percussion issue, Leslie motor issue, and any techs in Vancouver BC?

    Hi, I'm new to the forum. I live in Vancouver, BC and I've had my A-100 for a couple decades now and it fortunately has been pretty solid, but, alas, recently the percussion stopped working. I did notice that if I flip the percussion switch from off to on while playing, I will get one percussion 'ping' on any notes currently being held down, but that's it. No re-triggering from playing more notes. I know very little about Hammond repair other than soldering broken drawbar wires. :P I read online that the first thing to try is the percussion tube. I found diagrams of the preamp to guide me and tried swapping in a 12AX7 that I got from a guitarist friend. Should that work instead of a 12AU7? It made no difference for me.

    Given that I'm not great with electronics, I'm definitely not into trying this quick-fix "burn-off" described here. Is there anything else for me to try to make sure it's not just the tube? Other than that, am I best off trying to find a tech?

    On a different note, I have a couple Leslie's, a 45 (with amp) and a 740 modified with a 147 amp. They both started having issues a while ago sometimes not engaging the tremolo speed and now the 740 doesn't at all. The 740's slow motor is still working fine. The 45 is unmodified and just single speed. Is it most likely that the motors need to be cleaned or also possibly parts replaced? Is this also best done by a tech?

    Anyone have any leads on techs in the Vancouver area?


  • #2
    I had the exact same issue with percussion on my '65 A-102. I used the 9v battery "zap" method found here: I only did step 2 under "Zapping", where you unsolder the blue wire on the "K" terminal (5th from the left on the AO-28 preamp mounted upside down on A100) and touch to the 9v terminals and the amp chassis for a second or two, with switches in both on and off positions.

    As for the Leslies, check your belts first, they can stretch out or fray. Then check if the motors are turning but the drum/horns are not. Might need a little Hammond oil in the right places. For the 740 you could check the O-rings and the slow (small) motor spindle, make sure it disengages the O-ring when you switch to tremolo. Does the relay click when you flip the switch? If not it could be the relay or the switch. The 45 single-speed will probably need to be taken apart to service.

    Disclaimer: I'm not a tech, and I'm only familiar with the A-100 and a Leslie 120 I modified with a 125 amp and top horns. I found the motors to be easy to work with, but you'll have to decide your comfort level. And of course a tech is always your best bet.
    Hammond A-102 ('63), Leslie 122 ('63), Leslie 120 + mod horns, Yamaha SY-77, Technics KN2000, Fender USA Precision Bass (2016), Crown Micro-Tech 1200 x2


    • #3
      Thanks for all the info. I'll give all that a try.


      • #4
        I would zap as a last resort. There are actually three percussion tubes, and after 20 years of ownership, if you haven't changed the tubes it might be time.

        The cheapest, easiest & safest way to troubleshoot is with new tubes. Pick up two 6C4 tubes and one 12AU7A. The 12AU7 is the tube on the far right of the preamp as you stand behind the instrument. The 6C4s are the next two as you move to the left.

        When you replace these, you will likely need to adjust the percussion cutoff pot. It is super easy to do. Go to the B preset and push all the drawbars in. you can play a note and then adjust that pot on the preamp until you hear the percussion sound decay and not play a constant tone.

        The replacements shouldn't set you back much more than $30-40 CAD with shipping (but likely way less). I just picked up a few extra online 6C4s for ~7-8 CAD/each

        Read more here:


        • #5
          Hi Yiorgos.

          The percussion will be fixable, and will take trial and error. I have an A100 at a little log cabin in Montana, no techs anywhere near, so I had to do this myself over weeks (back and forth). I had the same problem. So I took the percussion tab box apart and sprayed it down with contact cleaner. Didn't work, but it was worth doing. I switched the AU7 for an AX7. No difference. I zapped like Greensweater. No go. It's hard to tell, because it would be nice to get some feedback while you're doing it, like sparks and smoke and explosions, or dendrites falling like hornets out of a sprayed nest. Finally, I switched the tube back to an AU7 and BINGO! Percussion working. I don't know why, but It was either the cleaning or zapping or both.

          The motors are easy to take out and in Vancouver an electric motor repair facility could get you up and running if the problem is limited to the motor.

          I'm in Alberta, but there are several forum members in Vancouver, especially Sweet Pete, and he can get you connected. Just watch and wait....

          1955 B3, Leslie 21H and 147. Hammond A100 with weird Leslie 205. 1976 Rhodes. Wurlitzer 200A. Yamaha DX7/TX7. Korg M1. Yamaha C3 grand, 67 Tele blond neck, Les Paul Standard, PRS 24, Gibson classical electric, Breedlove acoustic electric, Strat, P Bass, Rogers drum kit, Roland TD 12 digital drums, Apollo quad, older blackfaced Fender Twin, other amps, mics and bits and pieces cluttering up the "studio."


          • #6
            Thanks for the replies. I was going to follow the HammondWiki instructions (that greensweater linked) on measuring the voltages first to help troubleshoot if it seems to be a dendrite problem or a preamp/tube problem. I have a multimeter but I'm unclear as to which two points to measure the voltage across. The organ is at a friend's studio so I need to plan a little to make the best use of time when I go there.


            • #7
              I finally got around to troubleshooting the percussion problem. A friend was helping me by playing the organ while I used a multimeter to measure the voltage at the K terminal of the preamp, and then suddenly at one point the percussion magically started working again! This is after months of no percussion. I was dumbfounded but happy.

              Anyway, my problem with the Leslie I'm still trying to figure out. So the behaviour is that both the upper and lower rotors completely stop when I switch to fast/tremolo. The slow speed works fine with both rotors. When I flick the switch, I hear the relay click but both rotors stop and I see that the O-rings of both top and bottom motors have stopped. The tubes of the amp are all glowing. All 4 power plugs (upper fast/slow, lower fast/slow) are properly plugged into the amp. Again, this is a 147 amp in a 740 cabinet. What is the most likely scenario that would cause both motors to stop when switching to fast?


              • #8
                A bad relay may not be sending power to the fast motors. Swap the brown and white plugs and see what the new symptom is.



                • #9
                  If the slow motor armature isn't dropping away from the o-ring, it can on occasion bring the fast motor to a stop. Have a look at that.


                  • #10
                    Originally posted by Tim_at_Jonas View Post
                    If the slow motor armature isn't dropping away from the o-ring, it can on occasion bring the fast motor to a stop. Have a look at that.
                    I'll be taking a look at my Leslie (which is at a friend's space) tomorrow. I've never paid close attention to the motors so I don't know exactly what I should be looking for. Is it easy to see the armature dropping away from the o-ring while in operation and switching speeds? It might be hard for me to tell if something is not behaving properly since I don't have experience to use as a baseline.


                    • #11
                      You can download the motor assembly diagrams in the Leslie service manuals free from Captain Foldback.
                      There must be at least a few Youtube videos of the issue you are dealing with.
                      If you need o-rings,Fluid Seal on Bridgeport in Richmond has them.Wriason on Pandora in Strathcona/East Van too.Take your old one to match up what you'll need.
                      They are about .60 each.The 'city desk counter' is out back in receiving at Fluid seal,Wriason is up a set of stairs.

                      I use some sandpaper on new o-rings running on tremelo for a few seconds to give the speed change some 'bite'.They work best dulled,not shiny.
                      Once an o-ring develops a flat edge or has cracks,replace them to preserve the bearings on the chorale motors!
                      Replacement 'small' motors aren't cheap,and never work like the originals.
                      A100/251 A100/147 A102/222 B2/142 BV/147 BCV/145 M3/145 M102/145 M111/770 L101/760 T222/HL722 M111/770 no B3/C3!


                      • #12
                        Sorry folks, I think I tried this months ago and just forgot. It turns out if I switch the plugs I get the opposite effect, i.e. I get fast but not slow. Same behaviour for both upper and lower plugs/motors. So I guess it's not the motors? Wiring issue? Half-moon switch? Again, I do hear the relay 'click' when switching. I was in a bit of a rush but I'm going to go back in to see if I can measure anything at the plugs or anywhere else with a multimeter. Suggestions?

                        Sweet Pete, thanks for the local tips! I'll definitely keep those in mind. Btw, it would be great to meet you sometime and chat about Hammonds, etc. Do you play gigs in town at all? And do you know any local venues that still use a real Hammond organ? The only place I know is when Frankie's Jazz brings in a jazz organist from out of town (a few times a year) and they use an A-100 & Leslie (owned by Cory who used to run Cellar Jazz).


                        • #13
                          Relay or bad connection between relay and plugs.



                          • #14
                            Leslie sounds like a relay issue. Unplug the motors and plug in a small wattage lamp to test for power in each socket when you switch speeds, that will tell you if it's a motor issue or not, no power= relay issue.
                            A 12ax7 will not work as a replacement for the 12au7 in the percussion circuit of your a100. I found this out the hard way. Try a working 12au7. Pre amp caps may need replacing. This has been covered a few times in the past. If you were in Victoria I'd be glad to drop by and have a look, but I'm not a tech.
                            1962 A100, Leslie 145, Mini-vent., 1 Roland and 2 Yamaha pianos, Korg Micro X , Dave Smith MoPho, Nord Electro 3 with custom pedals and lower manual, plus assorted other stuff.


                            • #15
                              I tested the plug outlets of the amp with a digital multimeter. Sure enough, the fast side wasn't working. Only when I would hit the halfmoon switch from slow to fast there would be a split second spike to about 150V and then right down to almost zero (but not quite zero). The slow outlets were working fine, showing about 150V when on and then exactly 0V when off. I did notice that the longer I had the organ & leslie on, the voltage readings were increasing. Over a period of half an hour, the slow outlets went from about 140V to over 160V (when on). I hope that's normal. Is there any use in measuring any voltages coming through the Leslie cable or the connector box on the organ? Is it definitely a relay issue at this point? Does it mean anything that I can still hear the relay 'click'?

                              I might as well also mention this other issue I've noticed now that I've been swapping the plugs to get my tremolo speed. When I first turn on the organ and Leslie, I only get about half tremolo speed on the upper rotor. After the Leslie has been on a while, tremolo will spontaneously start working at full speed. I'm 99% sure it is the upper motor and nothing to do with the belt of the rotor. Also, touching the o-ring 'tire' lightly, it feels like it is spinning slower when I have the "half tremolo" behaviour and faster when the full tremolo speed starts working. Only after the Leslie is powered off for a long time (like when I come back a day or more later) will it do the half-speed tremolo thing again until it has "warmed up". I guess the first thing to try is oiling the upper motor. Could something in the motor stack also need adjustment?

                              So, I'm not very confident with electronics beyond simple soldering. I probably shouldn't be opening up the 147 amp and messing with high voltage electronics. I see a youtube video for replacing the 147 relay but I'm not sure I should be undertaking that task. I think I'll start looking for a local tech that can look into the relay (and the slow tremolo if oiling doesn't solve it). Really, my whole organ and Leslie setup could use an assessment in terms of what other things could be fixed/improved.

                              For now, I've got the fast motor plugs plugged into the slow outlets, so I basically have a single speed Leslie with the halfmoon switch backwards. :)

                              Thanks, everyone, for the help.