Tektronix 556 Fan Motor Repair Part 2
Tektronix 556 Fan Motor Repair Part 2
In this continuation of Tektronix 556 Fan Motor Repair Part 1, I have removed the motor and mount assembly and disassembled it. Now I need to figure out the problem and rebuild the motor.
Tektronix 556 Fan Motor Overview, mounted in place
556 Fan Motor Rear
Tektronix 556 Fan Motor removed from mounts. The Tektronix part number is 147-0029-00.
Tektronix 556 Fan Motor
Tektronix 556 Fan Motor removed from mounts.
Tektronix 556 Fan Motor
Tektronix 556 Fan Motor removed from mounts.
Tektronix 556 Fan Motor
The next few images show the disassembled parts of the motor:
Rotor, end bells and bushing assembly
556 Bushing Assemblies and Rotor
End bell inside, retainer, spring washer felt and bushing.
556 Fan Motor Bushing Assembly
End bell and bushing assembly
556 Bushing Assembly
Rotor and spacers
556 Fan Motor Shaft and Spacers
At this point I found several issues by visual inspection:
- The original rear bushing had been replaced, probably due to excessive internal wear.
- The replacement itself had excessive internal wear and it did not fit in the retainer properly due to its shape.
- The replacement bushing had been drilled off-center
- The bushing felts were stiff (almost solid) and dirty
- There was a large amount of solidified grease and dirt on the shaft and bushings
Original bushing is on the left, the replacement bushing is on the right.
556 Fan Motor Bushings
556 Rotor shaft, spacers and spring washer
556 Rotor Shaft and Spacers
Measurement of the rotor shaft showed that the wear was about 0.001″ undersize. This was not excessive, so I reused the shaft.
I cleaned all the parts (felts, end bells, shaft, rotor, spacers) and used mixture of teflon lubricant and non-detergent oil to lubricate the felts and bushings. I happened to have another fan motor with one bad bushing and one good one. Since the bushings are interchangeable, I simply replaced the defective bushing with a good one.
I also statically balanced the fan blade using jig originally intended to balance drone motor blades.
I re-assembled the motor and reinstalled it into the scope. The result was that the fan motor ran quieter than before, with little vibration and no rattling. This fan will never be whisper quiet as it moves a very large volume of air through the scope.
Thanks for reading.
Shaun M
