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Baldwin CT100D No Low C note sounding on bass pedals or octaves of both manuals

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  • Baldwin CT100D No Low C note sounding on bass pedals or octaves of both manuals

    Hello and forgive me if this has been discussed before,I tried search( and went down many interesting rabbit holes but no joy). When I depress the low C pedal on the instrument( with the round"C" combination button located between the two manuals depressed) and any one of the PEDAL stop tabs selected there is only a brief pulsing of the adjacent D note then silence. All other notes and tones of the PEDAL section play flawlessly. When I play any ACCOMPANIMENT or SOLO voice on either the lower or upper manual,each c key of each octave seems to sound thin and I believe is missing the C tone from the pedal section? All other notes and tones as well as the percussion and arppeigiator function work flawlessly. Ive located a row of circuit boards marked C thru C# which Im assuming are master oscillators(and possibly the dividers as well?). Ive worked in industrial electronics for 37 years but prefer working with schematics especially for an older musical instrument. Any guidance/links to schematics/manuals etc would be greatly appreciated to save this piece rescued from a church in upstate NY whos new pastor simply wanted to pitch it in the trash. It played fine for over a year till it suddenly behaved as described above last year. I have access to good DMMs and oscilloscopes.Kindest Regards to all.
    Last edited by Keys4JC; 02-01-2020, 10:14 AM.

  • #2
    So...an update... after a lot of schematicless probing and board pulling to determine function I found two things: an open line from the top of the C pedal section of what Im calling the Pedal PCB(two of the daisychained and covered with cardboard to cut dust)and a pin on what Im assuming is the "C" Generator/Divider board. This was determined by swapping with its good nieghbor C# pedal line and making measurements with the dmm also cross-swapping with the bad line. Once I got to the board I began diode checking the transistors and found one open circuit by comparing its measurements to all its nieghbours on the board. So I believe I have a bad divider stage. HERES the KICKER-in removing two known goodtransistors from other stages,these transistors(supposedly A696-PNP transistors according to the 2SA industry std) are reading good with the positive on the base! The bad one of course reads open on two pins both ways no matter what.All tests were made with the transistors out of circuit,and heatsunk with a crocclip before desoldering. Does anyone know if Baldwin has internal house numbers for the transistors or ? I assumed these were 2sa696 or "A696" and ordered a generic PNP replacement(set of 10 incase I had more trouble with other gen boards) but now with what Im reading with two different dmms its looking like I need to order the complimentary NPN version to see if I can get this working.So close...

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    • #3
      It’s been over 40 yrs but I think all Baldwin divider transistors were NPN, usually GE. Generic silicon like 2n2222 or 2n3904 should work. If you’ve found a bad divider it may be faster to replace both in that stage, or, ohmmeter each. If they ohmmeter out ok they should work. Good luck.

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      • Keys4JC
        Keys4JC commented
        Editing a comment
        Thank you, Sir for your time and advice.

    • #4
      Baldwin used the 2N2926 in tone generators of that era. How did you arrive at 2SA696?

      td

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      • Keys4JC
        Keys4JC commented
        Editing a comment
        Hi tuscondave : at the time I had no schematic and went by markings on the transistors which ,if interpreted by industry std part numbering for generic transistors led me to believe it was a 2sa696. Bazinga. It ended up being Baldwin numbers and I finally purchased a set of schematics from the good Mr. Spooner(the "last man standing" from the Baldwin Factory)and he was also good enough to point out the error with the transistor assumption.

    • #5
      So a happier update: With the aid of schematics purchased from the good Mr. Spooner(the "last man standing" from the Baldwin Factory) I was able to replace bad divider transistors in the C generator board. That and my previous repair of the broken wire from the C pedal trigger board to the generator board has yielded an operational instrument- save three 16' stops that will not sound. Mr. Spooner graciously pointed me to the accessory board which has the divider that handles these and this board is my next stop once I get some free time. More to follow, God willing.

      Comment


      • Keys4JC
        Keys4JC commented
        Editing a comment
        My apologies for not posting the transistor numbers I used: they are basically generic NPN crosses from NTE that seem to work just fine and are cool to the touch. Will need to dig up the bag.
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