Although this technical bulletin is based on scanner repair,
it is not the single source of vibrato problems.
Check existing switches, vibrato pre-amp. (tubes, etc),
phase shift line box, and cables both to and from the scanner.
||Vibrato Switch||Replace Switch
|Vibrato pre-amp. (Tubes, etc.)
||Replace tubes or other defective components.
|Open Signal Wire to Line-box
|| Replace wires or repair connections.
|Open From Scanner shielded cable.
||Shorted capacitors on line-box
||Replace defective components
|Open coils on line box
|Oil saturated Bakelite insulators which pick up impurities and
short out the stationary plates to the main assembly chassis
||Clean stationary and rotor plates and replace insulators,
isolating the stationary plates from the main chassis.
|Rotor plates rubbing against the stationary plates inside scanner.
||Check end play and height of rotor on gear and shaft assembly.
||Semi-frozen bearing on gear and shaft assembly
||Check oiling threads and for proper oiling.
|Poor tension on drive springs of the gear and shaft assembly.
||Replace gear and shaft assembly.
||Frozen bearing on gear and shaft assembly
||Replace gear and shaft assembly.
||Tension springs of the carbon brushes mispositioned causing the brushes
to make a squeaking sound against the rotor contact pins.
||Heat spring connection with soldering iron and spring will
fall into its proper position.
||Check for proper oiling.
Scanner Removal, Disassembly and Repair Procedure
- Detach motor and scanner assembly (A) from the generator assembly
by removing four (4) nuts from the synchronous motor which anchors
the motor to the "L" brackets of the generator assembly.
- Remove the cable connections in the organ so motor and scanner assembly
is free from organ.
- Note A.C., line box, and output connections for reassembly.
- Locate oil cup (B) and oil felt (C) inside cup.
The oil felt must be removed and the cotton threads unwrapped
from the felt before separating the scanner and motor.
Remove felt retainer spring (D) and lift up on the felt to remove the threads.
(Do this very carefully to avoid breaking the cotton threads).
After removing the threads from the oil felt take a pick or a paper
clip and remove the three threads from the one side of the oil cup
by pulling them through the hole in the cup.
The thread from the other side of the cup need not be removed.
- Locate screws (E) which hold the motor and scanner assembly together.
Remove the screws and pull the motor and scanner assembly apart.
Note: There is a gear on the end of the motor shaft and
must be guided through the hole of the scanner housing to separate the
motor and scanner.
- Remove two screws (F) from the rear cover (G) of the scanner.
Before removing the cover note that there is a shielded wire
attached to the cover.
This wire is connected inside the scanner and there is very little slack
in the wire.
Remove the cover and tip it back carefully so you can see inside.
Locate the carbon brush audio pick-up assembly (J).
The carbon brushes must be removed before the main housing
assembly cover (M) is removed, in order to prevent damage to the
carbon brushes and tension springs.
Lift end brush (I) and slip the two carbon brushes (H) off the rotor contact pin.
(Be extremely careful of the rotor contact pin during disassembly
so that you do not bend or break the pin).
Should it be necessary to remove the carbon brush audio
pick-up assembly (J),
desolder the audio wire from the brush assembly and
remove the two (2) screws (K).
To remove the end brush (I) remove screw (L) and separate from
the brush assembly.
- Remove the four (4) screws (N) and slip the housing cover (M) off the main
Note: Mark the housing cover (M) and the main assembly
chassis (U) to indicate the starting point of the scanner cable,
also mark the location of the cable clip (O).
- Stationary plates (P) and rotor (Q) are mounted on the main
assembly chassis (U).
Remove two (2) of the stationary plates (P), by removing screws (R).
When removing the stationary plates from the assembly you will
notice that there are insulator (S) and (T) on both sides of the
main assembly chassis, insulating the stationary plates from the
Then remove the rotor assembly (Q) by loosening the two (2) Bristol type
set screws (V), to avoid damaging the rotor contact pin during disassembly.
- Remove the remaining (14) stationary plates and insulators.
- Clean the stationary plates, rotor plates and other metal parts
using a Freon spray or other cleaning solvents that do not leave
any residue after drying.
An absorbent cloth or swab can be used in conjunction with the cleaner.
- Spray metal coated parts with Krylon Corona Dope (clear).
Caution: Do not allow spray to get on oil
threads or rotor pick-up pin.
- In most scanner repair you need not go further in disassembly than step
number eleven (11) but should conditions warrant further disassembly continue
with number thirteen (13), otherwise install new insulators and reassemble
- In removing the gear housing assembly (W) there are four (4) screws (X)
holding the assembly on to the main assembly chassis (U).
Upon removing the gear housing assembly you will notice the Bakelite
gear and shaft assembly (Y).
The springs on either side of the Bakelite gear also intermeshes
with the metal gear of the synchronous motor to drive the scanner.
- To reassemble the scanner reverse this procedure.
Transcribed July 16, 2001 by
Geoffrey T. Dairiki
from scans by