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Thread: Yamaha Electone C-405 Repair some functions

  1. #1
    ppp Pianississmo Kaibuki's Avatar
    Join Date
    Oct 2012

    Yamaha Electone C-405 Repair some functions

    Hi All,

    I am new in this very interesting Organ forum. Last sunday I found a very beautiful Yamaha Electone C-405 on a bulky waste. I played keyboard for 10 years but had a 10 years pause. Unfortunately I gave away my old keyboard and so I could not resist to take the Yamaha with me. The cable was cut, so I had not much hope that it is working. After opening and cleaning it very carefully and making a new power cable on it - it works and it sound really great. So not the worst idea to save it from the bulk. Unfortunately not all functions are doing well. I figured out two remaining problems:

    1. The rhythm generator does not start. When I hit the start button the first beat is played, the beat LED flashes one time, but then it stops immediately. When changing the type of beat I hear a difference in the first beat, so the selection seems to work. I got schematics from the C-605, which is very similar. I am not a specialist in reading them and unfortunately I have no oscilloscope. I figured out that there is a rhythm stop switch for the foot pedal. Perhaps this one is giving continuous signal to stop, or so?

    2. The special presets are not working. It has 7 special sounds like piano and others. But when selecting them nothing can be heard.

    Perhaps anyone has an idea of how to fix the issues or were to get the schematics of the C-405.

    Anything could be of help for me.

    Thanks a lot in advance.


  2. #2
    mf Mezzo-Forte fredy2's Avatar
    Join Date
    Feb 2005

    The rhythm stop switch would be a good place to start checking for the rhythm problem. I do not havee any of the schematics for these organs so I can't be of further assistance. Also check power supplies to the sections that are not working.

  3. #3
    pp Pianissimo winelight's Avatar
    Join Date
    Nov 2012
    St Albans, UK

    The schematics of the C-605 should give you good enough clues, generally these models are broadly similar and some of the boards are identical. As for an oscilloscope, I went to the trouble of making my own "sound card oscilloscope" interface board, but have never needed it yet - all the problems have been detectable / fixable by fiddling about or using a simple multimeter.

    Can't give any advice specific to this model without sight of the schematics - sorry. Generally though the boards all run off the same power supply, a -12V supply that comes along the metal rail the boards are mounted on. Some boards may need an extra supply or two such as -24V. These are worth checking as been suggested, and are usually labelled on the boards (if you can gain access to read them!).

  4. #4
    mf Mezzo-Forte Larrytow's Avatar
    Join Date
    Jun 2005
    Central Wisconsin

    The rhythm stop switch on the expression pedal is also used for the glide function sometimes. So, there will be a couple of rocker switches on the panel somewhere to select what function the footswitch is set to do. It could be that selector switch for rhythm stop is causing an issue.

    On the special presets, I think they can be assigned to either the Upper or Lower keyboard ? Is that selector switch working correctly ? Or dirty ? I'm going by distant memory here; never owned one, but have played a couple back in the day.
    Regards, Larry

    At Home : Yamaha Electones : EX-42 ( X 2 ), E-5AR ( X 2, one in parts, one not ), D80 ( in parts ), FX-1, FX-20, HS-7T ( in parts ), EL-25 ( X2, one chopped, one not ). Allen organs : T12-A, T-12B, ADC-6000D. Baldwin 626. Hammond Concorde. Lowrey CH32-1. A bunch of other Synthesizers and Keyboards. At Churches I play for : Allen Q325 ( with VISTA ), Hammond A105, Baldwin 720T, Several various small and medium size pipe organs of many sorts and builders.

  5. #5
    ppp Pianississmo sdavis's Avatar
    Join Date
    Aug 2013
    Georgia, USA

    Did you ever resolve the issue of the rhythm generator not starting? I recently acquired an Electone 7000 ('82) that has the same issue as you described. I had a Yamaha technician look at who works on the older Electones. He is stumped but believes it is not switch related. All his board testing showed no issues. He is presently researching possible causes.
    Thanks, Stan

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