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

  1. #1
    ppp Pianississmo funkyhammond's Avatar
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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. 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?

    Thanks,
    Yiorgos

  2. #2
    ppp Pianississmo greensweater's Avatar
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    I had the exact same issue with percussion on my '65 A-102. I used the 9v battery "zap" method found here: http://www.dairiki.org/HammondWiki/P...roubleshooting 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. #3
    ppp Pianississmo funkyhammond's Avatar
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    Thanks for all the info. I'll give all that a try.

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    ppp Pianississmo gaker's Avatar
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    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: http://bentonelectronics.com/servici...ype-pre-amp/#5

  5. #5
    p Piano Tonewheel's Avatar
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    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....

    Dave
    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."

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    ppp Pianississmo funkyhammond's Avatar
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    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. #7
    ppp Pianississmo funkyhammond's Avatar
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    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. #8
    fff Fortississimo geoelectro's Avatar
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    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.

    Geo

  9. #9
    ff Fortissimo Tim_at_Jonas's Avatar
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    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. #10
    ppp Pianississmo funkyhammond's Avatar
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    Quote 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.

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