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Thread: hammond H100

  1. #1
    ppp Pianississmo marshmite's Avatar
    Join Date
    Aug 2010

    hammond H100

    ive just purchased a lovely hammondH100.can anyone help with info on making it more B3ish,ie key clck etc im good at reading diagrams and soldering and used to valve gear.also what does the touch control tab do?thanks mike

  2. #2
    fff Fortississimo indianajo's Avatar
    Join Date
    Dec 2009
    Jeffersonville, Indiana

    H100's contain over 180 electrolytic capacitors, most of which are dried up unless replaced by previous repairmen. 115 of them are in the harp circuit, which I prefer in the dried up state. If you like keyclick, you will prefer that the keyclick suppression caps in the preamps stay dried up. The preamps are on the back of the keyboard.
    However, in the dried up state the power supply and power amp do not allow you hear the keyclick. Nor is the H100 thunderous bass apparent with dried up components. I suggest you check the motor cap (oblong near the motor) and the C702 and C703 caps on the power supply for production date. YYWW where year is 19YY. Anything over 20 years of age should be replaced or at least tested for capacitance and ESR at running temperature. The test is a very expensive proposition and I just replace them, myself. No Hammond supplied part (AO#) was an epoxy sealed capacitor IMO, hammond bought rubber sealed ones. If these 3 caps are new, they will prevent fires to the motor wire harness and add some bass and treble to the response.
    Capacitors store energy and should be measured at < 25 VDC to chassis before any metal is touched under the chassis. When measuring high voltage, use a clip lead on the negative probe to chassis so that only one hand at a time is used. Electricity crossing the heart is what can kill you. Wear no jewelry, as low voltage high energy can burn your finger off. Unplug the unit before soldering. Don't work alone. Don't talk to people while working around high voltage or high energy capacitors (>0.5 uf) of any voltage.
    The cheap way to replace the can caps ($30 each) with long life rated radial lead caps is detailed in this thread
    My H182 ser 11121 with just C702 and C703 replaced has substantial key click, but additional high response for proper OEM sound can be obtained by going on and replacing the electrolytic caps in the power amp. C401 is the can but there are several bass boosting axial lead caps under the deck. There is also a coupler cap to the reverb which typically inhibits function at this age.
    The axial lead caps under the deck in the power supply enable the "string bass" feature to work, which is a function making the pedal sound like a bass guitar IMO, making rock and roll and pop covers with the feet imitating the bass player possible.
    My "percussion" didn't work at all on ser # 9574 and #22?? , which makes touch control inoperative. For those not familiar with Hammond language, "percussion" is what they call the attack portion of the waveform, of the ADSR language describing synthesizer waveforms. Replacing C124 on the keyboard chassis pepped mine right up, but my early ones have the tube percussion chassis on the back of the keyboard chassis. Later ones have a transistor percussion amp there, which has several large aluminum electrolytics, and a couple of tantalums with a red end for the plus. Anyway, working, the percussion makes sounds at the beginning of the note only on the "B" preset key of the upper manual, and only when a percussion tab is depressed. With Touch control tab up, every key depressed makes the percussion sound. With touch control down, only the first key depressed makes a percussion sound, until all other keys are released. This is the way B3's etc executed percussion. With second voice tab down, the percussion harmonics sound continuously on UM B key sounds. Some people modify some of the percussion tabs to change the function to classic "twos" and "threes" sound, by bypassing across other harmonics. The banjo and guitar are two suitable tabs for modification, IMO. You may also use the back gang of the repeat function pot to make a variable decay function, like the slow/fast control on a B3.
    Another item needing attention are the power cord where it goes under the power transformer (the insulation falls off). A third item is the 10K 1/2 W resistors in power supply and power amp. The bubbled looking ones were too high in value and inhibiting full power in my units. Use 2-3W metal film resistors rated at 450 V or above, as vishay or multicomp versions.
    Bobmann is passionate about disassembling and cleaning the grease off the drawbars, but my early units don't have a problem with them. By the time I had learned to use the pedals (9 months of a couple of sessions a week), all the contacts but 1 were working. That percussion key contact cleaned up at about 18 months of playing, without disassembly. I understand that in later units, substantial amounts of grease were used on the drawbar contacts, which dry up and inhibit conduction. Bobmann107 videos on U-tube are worth watching.
    The schematics are available on Also on, and
    Don't neglect to lubricate the tone generator, and if square scanners, the scanner tub felt. Two funnels in the middle of the TG (one behind the harp panel) are best reached with a pump or squeeze bottle applicators. About 1/2 oz "hammond" oil in each funnel, enough in the tub to make the felt damp. Takes 2 weeks for the oil to soak in. "Hammond" oil can be bought from (MO) (Ontario) or in gallons as Mobil-DTE machine oil SUS 24 or 32. (Ensure the mobil grade you buy is the one not containing zinc anti-rust inhibitor, read the MSDS. The product available at was the safe one when I read it).
    High hours units may need one or both 5AR4 rectifier tubes replaced, for full power. Extremely high hour units may need one or more pairs of 6BQ5 power tubes or the 7591 pair of tubes replaced. #11211 had a pair of 6BQ5's, but I believe this was just because the church was too cheap to pay to have any caps replaced to cover the wimpy volume. The old tubes left in there, worked fine with the new C701 caps.
    Have fun. I love my #9574 with the 71 new electrolytic caps, I can make wonderful sounds and music with it. If only I hadn't destroyed the case moving it in. #11211 is the intact cased replacement, but with #9574 totally working, obviously this project has a lower priority than some others.
    Last edited by indianajo; 06-17-2012 at 12:54 PM.
    city Hammond H-182 organ (2 ea),A100,10-82 TC, Wurlitzer 4500, Schober Recital Organ, Steinway 40" console , Sohmer 39" pianos, Ensoniq EPS, ; country Hammond H112

  3. #3
    ff Fortissimo Bobmann's Avatar
    Join Date
    Jan 2008
    NC, USA

    I answered this in the Ham Zone as well; just in case you did not see that, or they delay posting for a while;
    Here is a link to a video that shows all the features of your H:

    I can't help with modifications; I choose to keep the H as it was intended...a great sounding organ.
    Trying to compare it to the A100, B3, C3, RT3 (all of which are pretty much the same internally) is apples and oranges...yes, they are both Hammond organs, and yes, you play them and make pretty music...that is where the similarities end.

    If you really want the "sound" that you perceive as the "B3 sound" you need to procure an A100, B3, C3, or RT3. Know that the biggest part of that sound probably comes from the Leslie speaker, which itself can be worth more $$$ than any model Hammond except the B3...depending on the exact model.

    The H is not a very popular model mainly because of it's reputation of being unreliable...IMO undeserved in the later models. Also the un-B3-like sound, the fragile diving board keys, and it's sheer bulk are draw backs. You can find these for sale at extremely reasonable prices; my feeling is that they are worth in the $100 range. I recently tried to GIVE away 3 of them...I never got so much as one nibble.

    After maintenance and replacing some components, it is as reliable as any organ of that era. It is, however, a real challenge to work on.

    In theory, there is no difference between theory and reality.
    In reality, there is.
    '54 C-2 & Pair of 122 Leslies
    H-324/Series 10 TC
    '35 Model A (Serial# 41) with a 21H
    Look at some of my rescues:

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