How To Rebuild The Drum Vibrato Scanner

This article explains how to rebuild the drum-type vibrato scanners. These are the type found on such organs as the T series, and are mounted parallel to the motor on a chassis. They are run by a belt from the end of the motor opposite the tone generator axle. (For information on the non-belt-driven scanners used in B/C/M-3's and the other older Hammonds, see HowToRebuildTheVibratoScanner.)

Often, the belt can stiffen at the curved ends and cause the scanner not to turn. The organ will still work, but the vibrato will simply not sound when you press the tabs. You can replace the belt with a simple rubber band or a similar-sized belt from your local hardware or power equipment store.

You may want to get hold of either a right-angle ratchet attachment or a hand-ratchet to fit in those tight spaces.

To remove the scanner, you must first remove the belt, which can be slipped off. Next, unscrew the ground cable from the right (non-belt) side of the scanner. Mark where it connects to on the chassis and the scanner. Put the screw back into the scanner.

Next, unscrew the four screws on each corner that are holding the scanner to the chassis. Remove the round wire harness if it is there. Remove the rubber o-rings and the bolts, but leave the metal axles there.

Now comes the hard part. Either you can unbolt the section of the chassis which has the motor on it, or you can squeeze it out. It's a real tight squeeze, but it it won't really damage the scanner unless you really try. Remove the 2 screws on the metal plate at each end, but DO NOT remove the metal plates until the scanner is all the way out. You'll have to be creative; twisting the scanner so that the axle and wire connecter+harness on the left end of the scanner can come through. This can be done by pulling out the right end first so it's at an angle, and slightly bending the metal bracket/chassis out to allow it to slide through.

Once it's out, you don't need to unsolder all those wires. Remove the two plastic ends. DO NOT DAMAGE OR BEND THE TWO PINS. On the inside are 16 capacitor strips. There shouldn't be ZincDendrites on the inside, but if there are, soak it in denatured alcohol. The wire clips are fairly strong and well-placed so you shouldn't need to re-do those connections.

Use a continuity tester or a multimeter set to ohms (should end up close to zero) to check the connection between the terminal on the left end (behind the plate you removed) and the pin it goes to on the vibrato board. Next, check the connection from the terminal on the right end to the ground screw.

Spray the two pins with DeOxit or a similar electrical cleaner. Use a cloth or your fingers to clean any gummed grease (gunk) from the gears. Spray the gears with Lithium grease ("White" grease) and spray the bearings also. Turn them to let it coat the gears. Try not to get grease on the capacitor strips or the electrical connections.

Next we move on to the brushes. In each end, there is a terminal, two springs, and two circular magnets on each spring with a brush going through it. Test the connection between the brushes and the terminal. DO NOT spray anything on the brushes except electrical cleaner if you so desire.

TopicRepair