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Troubleshooting

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Before you start repairing anything make sure that:

1. The tonewheel generator is properly oiled (the filler caps should be filled right up to the top at least twice but not to much!). After oiling it takes up to 2 weeks for some Hammonds to be 100% oiled. Be patient.

2. The motor is oiled - there are two little filler caps at each side of the motor.

3. All valves (tubes) are in place. You may need to use DeoxIT on dirty/oxidized contacts (pins and sockets). Simply spray on a dirty contact and wiggle the valve/plug to remove the residue.

4. There are no broken cables/connections between the amplifiers. Again, use DeoxIT if needed.

Those are the most common problems for newly acquired Hammonds. Cleaning the contacts, oiling the generator and motor will usually bring your dead Hammond to life and make all the squeaks disappear.

 

If you suspect one of the valves gone bad you should replace it before taking any further action. I myself have a spare set of valves just in case.

 

With your L100 series finding a source of a fault can be difficult since there are three amplifier units:

1. Preamp/Percussion Amplifier

2. Vibrato Amplifier

3. Power Amplifier

What I find really helpful is that you can easily bypass one or two amplifiers to narrow down the source of the problem.

On preamp/percussion amplifier casing there are multiple RCA inputs and outputs. They are marked BL (blue), BN (brown), BK (black), WH (white) and RED.

To bypass vibrato amplifier connect BN and BK - you will get slight volume boost and possibly overdrive on max settings.

To bypass power amplifier use WH output do hook the organ up to an external amplifier.

If disconnecting vibrato and power amp didn’t solve your problem - you need to concentrate on the preamp/percussion amp.

Next step would be checking for bad components and broken connections inside the suspected unit. If you are using multimeter to check the components for correct values check schematics and unsolder one of the pins if needed (the value of the resistance/capacitance between a resistor/capacitor pins may be different if there are any other resistance/capacitance paths between those pins).

 

Assuming that you have oiled the organ and cleaned all dirty contacts, these are a few problems and the possible solutions:

VOLUME DROP (overall volume drop)

  • Could be literally anything. If the overall volume (main + percussion) is weak start with power amplifier. Check for bad connections in the power amplifier first. Check the valves (just because they glow doesn’t mean they work properly).
  • Check the expression pedal for bad connections/resistors.

VOLUME DROP (main sound weak, percussion normal)

  • First check the 12AX7 valve (preamplifier).
  • Bypass vibrato amplifier to see if the volume is back to normal (if it is, the vibrato amp needs to be looked at).
  • Check the preamp circuit - take a good look at R206 - it is a high voltage resistor and often goes bad.

NO PERCUSSION

  • Check capacitors for broken wires (especially when you hear the keying pop/click but no percussion).
  • Check 12AU7 valve.
  • Check the connections in the tablet section.

NO VIBRATO

  • Obviously the problem is the vibrato amplifier or broken connections in the vibrato tablets. It is very uncommon problem and I have never experienced it.

CRACKLING NOISE AND/OR ‘THUNDER’

  • Could be bad resistor or capacitor or simply dirty contact.
  • First check if the noise is still present with percussion switched off. If not then take a closer look at percussion amp.
  • Bypass vibrato amplifier and power amplifier to check the source of the noise.
  • Once you have found the potential source, check the connections, plugs, sockets, valves, etc. Use DeoxIT if needed.
  • In my L122 the noise was caused by bad R206 in the preamplifier.

EXPRESSION PEDAL NOISES

  • Static when using the pedal - possibly the potentiometer but check the other components as well.
  • Scratchy sound, sometimes cuts off, sudden volume drops - use contact cleaner

MOTOR NOT STARTING

  • Check the run capacitor - you may need to replace it especially if it has already started to ‘expand’.

DRAWBARS PROBLEMS

  • For scratchy drawbars use DeoxIT on the contacts (yes you have to get to them from the bottom)
  • If your sound like they are set to 888888888 regardless of their position then you have a grounding problem. Check the wire that goes from ‘0’ bus (drawbar assembly) to the metal parts of the organ.
  • 888000000 does sound like 888111111 or 888222222? Again it’s probably grounding problem. Check the wire that goes from the TWG to the drawbars. The screw may need tightening or cleaning.