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Thread: M3 upper manual very faint/quiet

  1. #1
    pp Pianissimo wannab3's Avatar
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    M3 upper manual very faint/quiet

    Hello!
    Yesterday I hauled home an M3 in gorgeous shape that would've otherwise gone straight to the dump (true story...the gentleman servicing my dishwasher asked me out-of-the-blue "so do you know how to get rid of a spinet organ?") The serial number is 58145 which would date it to about '55, so it's one of the older ones, and it has some gremlins. Mainly, the upper manual is very faint compared to the lower one, not like when you enable percussion--it's just barely audible. The upper part also has a strange compression effect when you pull out more drawbars it seems like notes get softer, and notes are louder when you push all but one in. Percussion plays at normal volume when enabled. So far I've used deoxit on the drawbars, inside the main control panel, percussion switches, and for good measure I put a squirt in a couple tube sockets that looked iffy...none of that had any effect on the quiet solo manual (not that I expected it to). Any suggestions as to what I should try next? Could it be the matching transformer (and how would I test it)?

    Also the vibrato channel is very crackly and sounds like garbage. I think it's a bad tube but I'll need to get my tube tester out of storage to verify. I decided to measure continuity from the scanner housing to each of the output(?) lugs and got about 10K-ohms or a little more in each instance. Do I understand correctly that there should be no continuity between the terminals and chassis while connected?

    Provided I can get the upper manual to produce normal volume, my plan will be to also recap everything except the TG (for now) and replace any other out-of-spec parts. Oh yeah, and find a leslie...
    Last edited by wannab3; 03-21-2017 at 01:41 AM.

  2. #2
    ff Fortissimo Sweet Pete's Avatar
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    Welcome to the Forum.

    Congrats on your M3! Another rescued from the landfill.

    Crackly vibrato? Swap the 6AU6 tubes positions. They have covers and are next to each other. The tube # is stamped into the metal right in front of the tube.One is vibrato,the other non vibrato.
    If the problem becomes good vibrato and bad non vibrato it's a tube/amp/switch issue.
    Upper manual faint? Volume soft switch shorted maybe? Vibrato upper switch dirty maybe? Ground wire from generator loose? Bad connection or dendrites on the yellow and green wires in the matching transformer?

    Have you downloaded the service manual? It's free at Captain Foldback.

    I'm sure to have missed something so others will be along to help out too!
    Have fun!
    Pete
    A100/147 B2/147 A102/222 M102/145 M111/145 L133/770 1937 Northern Hammond(third one built) BCV/122 NordStageEX88 Yamaha MOX6,Neo Ventilator
    Radial J type DI's ,Mogami Starquad wiring ,Yorkville Powered Speakers,Allen+HeathMixWiz3,Soundcracft LXII7/24,SWR Pro220 bass amp,Fender ProReverb

  3. #3
    pp Pianissimo wannab3's Avatar
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    Pete, thanks for the suggestions. I do have the SM downloaded and have been studying it (I can't imagine working on the organ without it!). I grabbed my tube tester and found the 12au7 in the vibrato amp was bad...after replacing it with a good one from my stash the vibrato distortion is gone. A couple other preamp tubes test weak (the 6C4s) but I'll have to order replacements online. The vibrato sounds choppy after a few minutes of operation...I'm guessing I'll want to rebuild the scanner and probably recap the line box, but first order of business is getting the solo manual to work correctly.

    I looked into it some more today but had no luck getting more volume out of the upper board. All the ground wires are intact and connected, and I could see no obvious path to ground through dendrites...but the plate the transformer assembly is mounted to (the piece that gets fastened to the manual) sure looks a little fuzzy. I clipped my DMM (ground ref. on TG chassis) to the transformer output for the lower manual and played its middle C with just the fundamental bar drawn and measured about 37mV. When I moved the clip to the output of the upper manual and played its middle C I got nothing. I also tried directly grounding the 'low' side of the transformer by bypassing R2 ...no dice. Switches have been thoroughly cleaned with deoxit and all contacts test <1 ohm. I also found no low-resistance shorts to ground from any of the switch contacts.

    Tomorrow I'll start dividing and conquering with my desoldering iron...I'm outta steam and need to call it quits for the night.

    Anybody here in the Willamette Valley, OR willing to help me get it working? I'll buy the beer

  4. #4
    ff Fortissimo Sweet Pete's Avatar
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    1 members found this post helpful.
    Make sure the upper drawbars aren't shorting. Follow the bundle to the manual from the MT's.
    Sometimes reflowing solder gives the atrophied component a wake up call....sounds like you have a short in the upper drawbars.
    Reflow all the connections in the MT's.
    At the end of the drawbar assembly make sure no wires are off or touching other wires.

    I'm done after a long day too.
    A100/147 B2/147 A102/222 M102/145 M111/145 L133/770 1937 Northern Hammond(third one built) BCV/122 NordStageEX88 Yamaha MOX6,Neo Ventilator
    Radial J type DI's ,Mogami Starquad wiring ,Yorkville Powered Speakers,Allen+HeathMixWiz3,Soundcracft LXII7/24,SWR Pro220 bass amp,Fender ProReverb

  5. #5
    pp Pianissimo wannab3's Avatar
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    1 members found this post helpful.
    Success! After retouching all the solder joints in the MT (including the white jumper wire between the coil halves) I now get sound from the upper manual. While I was in the area I dismounted the transformers and terminal strip from the plate and shaved off all the dendrite crystals that had grown (some were an 1/8" long!). I also thoroughly cleaned the drawbar assembly using deoxit and a pink eraser on the silver contact strips...now they work like new.

    Hopefully I'll tackle the scanner this weekend... I'm slightly nervous about doing that because some days I can be a bit of a klutz.

    I was thinking about ordering the AO-29 recap kit offered by TWG...while I'm at it, I think I'll add a fuse to the primary side of the transformer. Would a 1.5A slow-blow be appropriate?

  6. #6
    ff Fortissimo Sweet Pete's Avatar
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    Recapped an M3 amp with a kit from TWGH a few years ago with great results!
    A 1.5 slow blow should be enough to save the PT in a failure situation.
    I have had to replace the 10 watt safety fuse off the rectifier after improperly installing a 5U4 with no guide pin so there is a fail safe built in......a fuse will save that resistor.
    Enjoy your new M3.
    I keep one around.
    Great sounding organ that is as close to a B3 as it gets!

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