Conn 640 bass adjustment

[Guest]

I just bought a conn 640 organ and cleaned it up. Had to go into the bass and adjust some of the contacts. Now it is out of tune. Does any one know how to adjust the pots for the bass section? I have a cromatic tuner but not sure where to start and what sequence to go. There are 2 master tuning pots and one pot for each pedel.

Have not seen any manuals on the internet either.

Dick Bishop

[jbird604]

Re: Conn 640 bass adjustment



Before you even start this, sweep each of the pots -- master and individual -- through its entire operating range numerous times to clean the wiper. If the pots are really dirty you may need to apply WD-40 or some other cleaner. Otherwise the pitches will jump around like crazy when try to tune.

Also, be sure the little spring-type contacts in the rear of each pedal switch are very clean and making good contact.

To do a complete pedal tuning "from scratch" you can set all the individual pots in the "12 o-clock" position, then use the master control for each octave to get the note G in each octave in tune. Then tune the individual notes in each octave. It doesn't matter about the sequence in which you tune them. Only the master affects all the notes in its designated octave. The rest of the pots affect only the note marked.

If you should find that some note will not tune, you may have to re-adjust the master for that octave, then start over.

But the tuning range of each note is so huge that you will surely be able to get them all right unless there is something drastically wrong with the tuning switches (springs) or in the oscillator circuitry.

John

[Guest]

Re: Conn 640 bass adjustment



Thanks John, I have some very good contact cleaner. I will try this proceedure in a couple days and post how it worked. I am also trying to get a manual from Organ service Corp.

Dick Bishop