Rebuilding A CD45II or Similar Rotor

A few months ago my rotor failed and I had to replace the bearings. Well, I was telling someone on the local repeater that I was on my way home to place the repaired rotor back in its rightful place when he explained that he had purchased one off E bay and it will not turn with any weight on it. He was going to send it off for repair but with shipping and the cost of repair he was holding off until his tax refund was received. I asked if he would like to bring it over and we could do the repairs needed and that he could save a bunch. He was thrilled. Below is step by step of what was needed to repair his rotor to new again. A footnote, total repair cost was less then the freight charges would have been!

Materials needed: Brake cleaner (Brakleen from NAPA), Thimble of low temperature white lithium grease (Garage door lithium grease works well and is good to -20 degrees plus it?s available most anywhere), soft brass ?tooth brush? style brush, appropriate size open end wrench & flat head screw driver, clean rags. A small fine metal file might, but hopefully not, be needed. Put all hardware you remove in a baggie so nothing gets lost.

First place the rotor in a vise with the top V portion of the mast clamp facing toward the bench (if present remove bottom mast support first) then remove the 4 bolts on the bottom that hold the motor/pot/gear assembly. Carefully lift straight up and remove the bottom plate to expose lower bearings and set the assembly aside. Carefully remove the nylon bearing retainer with bearings, the nylon retainer is split so locate where the split is and with one hand under the split and the other hand on the opposite side of the split lift it out keeping the assembly level. Place it on clean surface or towel.

Place some of the brake cleaner in a small can, remove the bearings from the nylon holder and place the bearings in the cleaner, while they are soaking inspect the bearing roller track of the lower housing cover you removed and remove all the old grease and grime using the brake cleaner and brass brush. If there are any rough spots or burrs remove with a fine file. Now inspect the nylon retainer and bearings if they are good clean them thoroughly, if not order replacement retainer and bearings from Hy Gain.

Problem 1: Damaged nylon bearing retainer removed

Now remove the 2 nuts and lock washers holding the motor and wiggle back and forth to remove motor and pot as one unit. You do not need to disconnect any wires for removal. Push the motor/pot off to the side out of the way of the plate that holds the gears in place. Inspect the pot and clean with some contact cleaner if necessary.

Motor & Pot Assembly Motor & gear retainer plate removed

Now with the motor removed inspect the gears for wear, the top portion of the gears are usually OK it?s the pinion gears attached to the bottom of the reduction gear that needs to be carefully checked and are usually what?s damaged. There are 4 gears, the top 3 are all the same gear and pinion, the 4th is zinc and has a longer pinion gear and the bottom is 3 gears together with no pinion to form the spur gear that drives the larger main gear. If the spur gears are worn a complete gear kit can be ordered from Hy Gain or individual gears can be purchased. Next remove the main drive gear, this is done by lifting up on the gear from the opposite side of where the smaller reduction gears are located to an angle of 30 to 45 degrees and pulling the main gear up and out. Inspect it for any signs of wear and order a replacement if necessary. If OK then clean with brake cleaner and brush & lightly lubricate.
Main Drive Gear Cleaned Problem 2: Bad pinion - 3rd gear down

If any or all of the gears need replaced remove the 3 screws holding the gear retainer plate in place using a flat head screw driver, lift off being careful to retain the washers on top of the studs holding the plate in place and push the bracket off to the side allowing access to the gears.

Left: Gear retainer plate removed Right: Gears ready to lift off and be replaced

Before replacing lightly lubricate all the gears as well as the studs they fit on then stack the new gears in the order they will be placed on the studs as well as noting where any spacers and washers are located. (in case you run for a beer and forget) Note that there is a small spacer and washer on top of the 2nd gear down and a larger one on top of the spur (3 gears together) gear as well as a stud that holds the 3 spur gears together. BEFORE REPLACING THE SMALLER GEARS INSTALL THE MAIN DRIVE GEAR, the tabs face up on the main drive gear. Also make sure flat washers are on top of the studs for the gear retainer plate and the spacers. (See exploded view at end of article)

Next replace the gear retainer bracket making sure the washers are on top of the studs. Now lubricate the two studs that hold the motor with some grease and replace the motor.

New gears installed and retainer plate and motor in place.

Next rotate the upper spur gear until the inwardly protruding stop on the main drive gear touches and just opens the left of the U shaped limit switch (viewing with the limit switch towards you). This is the clockwise end of rotation. The potentiometer arm should now be moved to its extreme clockwise position against the potentiometer stop.

Bottom of picture shows the stop resting against the U shaped channel stop lever.

Top of picture shows potentiometer arm (left side of picture) fully clockwise against stop.

Now replace the upper nylon bearing retainer and bearings, lightly grease the nylon retaining ring as well as the rail & bearings.

New upper nylon bearing retainer and bearings greased and installed.