Maintaining the organ
Physical layout
Console
Removing side and back panels
The side and back panels are held in place by magnetic fasteners located on the inside of the panels near the top. To remove a panel, attach a suction device to the panel near the top and pull out.
Swell/Choir side
- Stop contacts (Swell and Choir)
- Piston relays
- Florescent starters (3)
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This picture shows the wiring for the stop switches on the Swell and Choir manuals. There is a diode in series with each switch that allows banks of switches to be "preset" for particular "combinations" and selected via the "piston" relays. The circuit diagram is on page xyz of the Maintenance Manual.
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These relays are controlled by 20 push-buttons ("pistons") and cause the desired preset combination(s) to become active. The circuit diagram is on page xyz of the Maintenance Manual.
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These are the starters and ballasts for the 3 flourescent lights on the Swell/Choir side of the console. If a light is not working properly, the cause can be either a defective light or starter. The circuit diagram is on page xyz of the Maintenance Manual.
Back
- Pedal switches
- Coupler gang relays
- Variable power supplies (4 – one for each organ division) that supply power to the oscillators
- Oscillator “attack” resistors
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Great/Pedal side
- Stop contacts (Great and Pedal)
- Florescent starters (5)
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Oscillator racks
Introduction
- Great
- Pedal
- Swell
- Choir
Stop filter boards
Introduction
- Great
- Pedal
- Swell
- Choir
Speaker matrix
Introduction
Loudness-adjustment resistors
- Great
- Pedal
- Swell
- Choir
Power amplifiers & speakers
Introduction
- South loft
- Balcony
- North loft
Trouble-shooting
This organ has been in continuous operation since 1966---a period of over forty years. Most recurring operational problems have had a small number of causes, such as corroded contacts or blown fuses. Following is a list of the most common problems along with the probable cause(s).
Problem: No sound from a single stop.
Probable cause: Dirty or corroded contacts on the stop tab switch or a bad solder connection on the on/off relay on a stop filter board.
Problem: No sound---or weak or distorted sound---from several stops that speak from the same loft.
Probable cause: Blown fuse in a power amplifier OR a defective power amplifier. These problems are usually due to a power surge caused by a nearby lightning strike.
Action: Identify the location of the problem amplifier. Remove the amplifier and check for blown fuses. If a fuse is blown, replace it (or them). When the amplifier is re-inserted, either the problem will be solved or the fuses will blow again. If a fuse blows again, replace the amplifier. The root cause was likely a shorted output transister in the power amplifier.
Problem: No sound---or weak or distorted sound---from a larger group of stops that speak from the same loft.
Probable cause: Blown fuses in several power amplifiers or a blown fuse in a power-amplifier power supply.
Action: Identify the locations of the possible problem amplifiers and follow the above procedure. If no fuses are blown, check the levels of the + and - supply voltages. They should each be about 20 volts. If a voltage is not present, check the output fuse and replace it if blown.
Problem: No sound from all stops that speak from the North loft.
Probable cause: Tripped circuit breaker in narthex power panel.
Action: The circuit-breaker panel is in the northwest corner of the narthex just inside the door at the top of the steps from the back parking lot. Reset the breaker marked "organ."
Problem: No sound from one or more notes coupled from another manual.
Probable cause: Dirty or corroded contacts on one or more coupler gang relays.
Action: Identify the problem relay and spray contact cleaner on the relay contacts. Then cycle the coupler on and off a few times to wipe the contacts clean. Repeat this action if needed.
Problem: When a pedal key is pressed, either there is no sound or there is sound from two notes.
Probable cause: One or more misaligned pedal switches.
Action: The pedal contacts are hermetically sealed and each is operated by a small moveable magnet that is fastened to a small aluminum plate mounted at the end of the pedal key. The position of the plate can be adjusted with a screwdriver. Remove the console back panel for access.
Problem: Unstable pitch on a single note.
Probable cause: Loss of beta in an oscillator transistor.
Action: Identify the oscillator board containing the problem transistor, and replace the transistor, which is an RCA 2N591. It may be necessary to obtain a 2N591 from a Pedal oscillator board that has unused oscillators. The top Pedal note is "G," so the top oscillators boards have 4 oscillators that aren't used: G#, A, A# and B.
Problem: Non-operating---or flickering---flourescent light bulb.
Probable cause: Defective light bulb or starter.
Problem: No sound for a single key (i.e., C, C#, D, ... etc.) at a single pitch (i.e., 16', 8', 4', ... etc.).
Probable cause: Problem with a single oscillator.
Problem: Difference in sound quality for a single key (i.e., C, C#, D, ... etc.) at a single pitch (i.e., 16', 8', 4', ... etc.) compared to that key's neighbors.
Probable cause: Problem with the rectifier circuit on a single oscillator.