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Flashing sometimes will (at least temporarily) fix a moatorboating vibrato. (See ManualZapping for some hints.)

Also note that if any of the wires leading to the scanner are broken (or connected in the wrong order) your vibrato will not sound right.

Rebuilding the Scanner


Also, please see the Hammond Technical Service Bulletin on Repair & Disassembly of Vibrato Scanners at http://www.dairiki.org/hammond/vibrato_tsb/.


Note: To rebuild the drum-type scanners attached to the motor by a belt (not mounted to the end of the motor) such as those found in the T series, see HowToRebuildTheDrumVibratoScanner.

The following was submitted by BobSchleicher to the OriginalHammondLeslieFaq.


The presence of a motorboating or chopping sound in the Vibrato can be an indication that one or more pole pieces of the Scanner have been shorted out. The likely culprit is a crystalline growth that can occur on the plated and metal composing the scanner housing (ZincDendrites). This shows up as conductive whiskers or dust between the scanner body and the poles of the scanner. High humidity and temperature is said to aggravate dendrite formation. An over-oiled scanner can also cause vibrato motorboating, though it is probably an aggravating condition to the dendrite formation. The oil coats the insulators and picks up and retains conductive dust and debris, shorting out the stators.

A Hammond technical bulletin was issued detailing corrective procedures to cure this condition. What follows is a shortened version of it:

Before you condemn the scanner, be sure the rightmost ?6AU6 is healthy. Swap with the other one to verify. If you still have the problem, measure the plate and screen voltage on V2. They should measure about 130VDC and 60VDC respectively. Plus or minus 15% is O.K. If the problem persists proceed as follows:

Notes

You shouldn't need to, but if you want to remove the rotor from it's shaft, you'll need a BristolWrench.

Make sure you clearly mark where the red & blue wires go. Do not use a magic marker that washes off when you thouroughly clean the scanner assembly.


External References

The following is a very detailed set of instructions and photos that are extremely useful while doing your first Scanner rebuild:

http://avintagesound.com/REBUILDYOURVIBRATOSCANNER.aspx

Here is another set of notes, based on a Hammond service note:

http://www.bentonelectronics.com/vibrato.html

TopicRepair

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