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Rebuilding CD45 and Similar Rotors

Steve Fetter (WA8UEG) on August 10, 2013
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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.


rotor 003Problem 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.

rotor 005

   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.

rotor 013        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






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.


Retainer ring        New upper nylon bearing retainer and bearings greased and installed.


















Next grasp the operating mechanism by the base and steady the ring gear, invert the assembly and lower it into the housing. The serrated portion of the potentiometer arm must engage into the drive boss located at the bottom of the housing, the three drive bosses on the main gear must fit into mating recesses in the top housing. All this will go right together with no problem if you have followed the instructions. (secured V portion of mast support toward bench, rotated the gears so the stop just opens the switch, set the pot to it’s full clockwise position)


Next place the lower nylon bearing retainer and bearings in the bearing race (lightly greased) and place the bearing retainer ring on lining up the four holes with the threaded holes in the housing. Tighten the four screws to 85 inch pounds if you have the right tool or just completely tighten with a large screw driver.


I suggest that the control box be hooked up and the rotor tested prior to placing it back in service. Connectors for the control box can be purchased off E bay and a short control cable can be made for testing purposes.


This rotor was a disaster when we opened it up and now looks and runs like new!

                                                                     Lower bearings in place and rotor ready to be placed in service

Bottom bearings 001j                                                               























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Rebuilding CD45 and Similar Rotors  
by WT8E on August 10, 2013 Mail this to a friend!

What were the symptoms of the failed bearings in your rotor? Also what did you find in your friends rotor that caused the failure? This might help someone in repair of their rotor.

PS; Nice job, explaniations and pictures were great. I was waiting to see how you addressed the direction wiper.
RE: Rebuilding CD45 and Similar Rotors  
by WA8UEG on August 10, 2013 Mail this to a friend!
The bad bearings and bad bearing retainer caused the indicator pointer on the control box to be erratic (kind of jumping)rather then moving smoothly (same with mine). The cause was attributed to the grease used becoming hard and brittle. When most people grease the bearings they use way to much, my friends looked like wheel bearing grease had been used and it was packed in like someone was packing a wheel bearing. Of course the bearings as well as the gears are turning at a very slow speed and just need a very thin coating of a low temperature grease. On mine the grease was also applied heavily and it also had become very stiff not allowing the bearings to roll as they should.

Thanks & 73
Steve WA8UEG
RE: Rebuilding CD45 and Similar Rotors  
by G3RZP on August 10, 2013 Mail this to a friend!
The ball bearings are 3/8 inch and likely to be much cheaper bought from a local bearing supply shop. You may well find the balls are corroded, and the last thing you want is corroded balls. Change them in that case. I found that the T2X (similar but bigger than the CD45) terminal block corroded and I went to a blanking plate and a cable gland with a pigtail lead from the rotator. Some PVC plumbing stock contains the join to the main rotor cable.

I was using the tower, top loaded by the beam, as vertical on 80 and 160. This meant some RF flowing through the direction indicating potentiometer, and it burned up. On the replacement, I used 0.01 microfarad disc ceramic caps to bypass it, and a strap from the tower to the stub mast above the rotator.

A good idea is to have the rotator in a 'cage' with a bearing for the stub mast above it. To check that the stub mast really is concentric with the bearing, measure the motor current as you run the motor round: it should stay constant. I use a Yaesu bearing.

I had trouble with the bolts holding the T2X down working loose, despite using Loctite and single coil spring washers. I now have a plate that clamps over the Bolt heads, which has put an end to that problem.

I have both a Ham 4 (VHF tower) and T2X (HF tower, turning a 4 el SteppIR): both have been up for over 25 years with just occasional servicing.
RE: Rebuilding CD45 and Similar Rotors  
by WA8UEG on August 10, 2013 Mail this to a friend!
Mine is in a home brew cage with a TB3 thrust bearing holding a MA40 tubler tower with a full size quad (picture link on my QRZ homepage) The CD45II has been turning it for 10 years here and 8 years at a past QTH.
36 years and going strong!  
by W8KQE on August 10, 2013 Mail this to a friend!
I'll keep this article in mind, but i've had my CDE medium duty rotor and control box since I first got licensed in high school back in 1977, 36 years ago! I am turning 52 this year. I've never opened it up or done any maintenance on it whatsoever, and it still works perfectly like it did when new. It's been used at 3 QTH's, and has never failed to turn my Mosley TA-32 and 33 'Junior' tribanders all these decades! Blows my mind! Unbelievable! Best made product i've ever owned!
RE: 36 years and going strong!  
by AA4PB on August 10, 2013 Mail this to a friend!
The biggest problem that I have with these rotors (a HAM4 in my case) is that the POT gets bad spots that causes the indicator to jump around as you rotate it. I expect that some of that comes from leaving the antenna parked in the same position (into the wind) when not in use. The slight play in the brake system wears a spot on the pot.
RE: 36 years and going strong!  
by G3RZP on August 10, 2013 Mail this to a friend!
A worthwhile mod was a 22 ohm 3 watt w/w resistor in series with the lamp - still on the original lamp. I did have the electrolytic go bad, but I substituted a 50 + 50 mFd 350 volt electrolytic: insulate the case and use the two sections in series as a non-polarised electrolytic. Been working OK like that for 20 years.
Rebuilding CD45 and Similar Rotors  
by K0RS on August 11, 2013 Mail this to a friend!
Good article. Directions given here apply to all CDE/Telex/HyGain rotors. Working on these rotors is mostly common sense. Unfortunately the word "common" is an oxymoron here.

One mistake frequently made when working on these rotors is using too much grease on reassembly. The manual cautions that only about a thimbleful is required.

For those jittery direction indicators, inspect the pot for aluminum flakes and clean with contact cleaner. The brass plate that engages the bosses cast into the upper rotor housing wears the aluminum and the dust falls onto the pot coils causing intermittant contact with the wiper.

Shimming the gears is important. Shim them so the gear teeth engage their mating gear teeth fully and the gears don't rub on one another. I've seen many poorly shimmed from the factory. Shim locations aren't necessarily standard from rotor to rotor. Some extra shims are handy.
RE: Rebuilding CD45 and Similar Rotors  
by WA8UEG on August 11, 2013 Mail this to a friend!
A few comments: W8QUE - They are great rotors, I have had mine for about the same amount of time. Eventually the grease will go bad, it becomes wax like and will need cleaned out but once every 35 or 40 years isn't bad!!

AA4PB - No doubt the pot will cause the indicator to jump also and as mentioned in the article should be inspected and cleaned when your in there but the bearings sticking and not rolling will also cause the problem. I would suggest checking everything out if the meter starts to jump. Catching the problem early will save having to purchase new parts.

G3RZP - That's a great mod! The lamp is a real pain and always goes out during a contest in the middle of the night when you need it. I would have done this mod had I known but I converted my meter illumination to LED which was more difficult but does do a very nice job.
RE: Rebuilding CD45 and Similar Rotors  
by AA4PB on August 11, 2013 Mail this to a friend!
The one time I did have bad bearings I could see the antenna "jump" as it was not rotating smoothly. Most of the time the meter jumps but the antenna rotates smoothly.

Cleaning or replacing the POT is not a big deal but getting the rotor out of the tower and down to the work bench is. At best it is an all-day project plus the repair time. The last time I did it I purchased a new rotor from one of the shops with the agreement that I could send in the old one for a rebate when I got it down. That way I didn't have the antenna sitting on the ground for a week or more while I ordered parts and repaired the rotor.
RE: Rebuilding CD45 and Similar Rotors  
by G3RZP on August 11, 2013 Mail this to a friend!
The direction indicator pots are pretty expensive. The one on the VHF tower decided to open at one end, and I cheated. I used a 2N3819 FET as a constant current source and fed the current through the working section of the pot to ground. This gave a voltage directly proportional to the position and a simple op-amp is used to drive the meter. So I had to design and build some simple electronics - took an afternoon - but saved the cost of a pot and the effort in taking the tower down.

On the T2X, the brake wedge can be a bit hard to disengage, especially if there is wind pressure trying to turn the beam. I have an arrangement that when one presses the brake release, 230 volts goes across the primary of a 115 to 6.3 volt transformer, and the resulting 12 volts goes in series with the 28 volts to the brake solenoid for about 500 msec. That works! Then a slow release relay is arranged such that the brake cannot engage until about 2 seconds after power is removed from the motor, preventing the brake slamming home while the motor is under power. It also lets the motor slow down rather than strain the gear train.

Little things, but I suspect incorporating them new from the factory would shove the price up quite a bit.
RE: Rebuilding CD45 and Similar Rotors  
by N6AJR on August 11, 2013 Mail this to a friend!
And take pictures before and after every step. It will help immensely when you go to put it back together. !!!

RE: Rebuilding CD45 and Similar Rotors  
by WA8UEG on August 11, 2013 Mail this to a friend!

Your right about that getting it off the tower is the major job. For the past 35 years or so I have mounted mine 3 ft or so above ground and use a thrust bearing toward the top. I ran about 60 ft of mast from my bearing to the rotor located on a plate near the base with my 70' tower years ago. Guess what, never had to remove the rotor but if I did it would have been a snap. My current set up takes only 5 minutes to remove or replace the rotor, it only sits about 7" above the ground.
RE: Rebuilding CD45 and Similar Rotors  
by G3RZP on August 12, 2013 Mail this to a friend!
Total thread drift......

Before CB became legal here, a guy without planning permission (zoning) put up a 60 foot tower in his
yard. On this, he put a CB vertical and I believe, a CD45 - might have been a Ham IV! - to rotate it. With an illegal amplifier, he caused enormous amounts of RFI before being shut down and fined...... and had to remove the tower.

Who was it said that there are no limits to stupidity?
RE: Rebuilding CD45 and Similar Rotors  
by WA6ITF on September 4, 2013 Mail this to a friend!
While a bit off topic, back in the early 1960's, on the advice of the late Larry Levy, WA2INM, I bought a brand news CDR AR-22 TV rotor for all of $39 or so.

It initially held a 3-element 6 meter Hy Gain yagi. Over several moves and re-installations, its last mission was to rotate a pair of 26' 6-element Hy Gain 6 meter "Long Johns" stacked with a pair of Cushcraft 17 or 18 element 2 meter yagi's. Definitely well beyond the rotors rated wind load and turning power.

But surprise, surprise: It held up fine with that load atop a 7 story apartment house on Bay 19th Street in Brooklyn NY some 17 feet above the roof-line on a piece of 2 1/2" heavy wall Dural aluminum piping all clamped to the side of the elevator control house with six standard TV antenna "W" mounts that were bolted to the bricks with standard studs shot in.

I had two sets of guys -- one about 2/3 up the pole and the other at the rotor itself. In all the years I had it, no matter how badly I treated it that poor inexpensive rotor it simply refused to fail.

Yes, winds would occasionally blow it out of calibration, but a simple end to end rotation would re-calibrate it.

When I took it down in the fall of 1972 (along with the antennas) prior to my move out to Los Angeles I gave it to a friend who was in need of a small rotor for his 7-element 2 meter Hi Par antenna. He used it for the better part of another 20 years unyil he became an SK.

Keeping in mind that this was a light duty TV antenna rotor, that kind of service was astounding and says a lot for the quality that Cornell Dubileer Radiart put into its products back then.

Oh yes, somewhere in my collection I have color slides of that monster installation that kept me on the air the last half decade I resided in the City of Angels. If I can find them, Ill scan them and put them up on Facebook with some of the other photos from that era already there.

PS: The only nrgative was the "clunk-clunk-clunk" the control box made as it twirled the antennas three stories above -- but that only annoyed me, the dog and eventually thew wonderful lady whose been my wife the past 42 years.

-- de WA6ITF
RE: Rebuilding CD45 and Similar Rotors  
by WA8UEG on September 5, 2013 Mail this to a friend!
I used one for many years turning a Mosley 6 element wide spaced 6 meter beam. It worked fine, the clicking was annoying. I had a routine when I came into the shack to operate because it only took a small wind to knock it off course. Rotate the beam clockwise to north then counter clockwise to north then flip it over and press the metal tab on the bottom of the indicator box till it was at north. The only other problem was the cap inside the indicator box was only good for about 3 years. I finally found a quality motor start cap at Granger that solved that problem. Ahhhh, the good ole days!
Rebuilding CD45 and Similar Rotors  
by KG4BFR on October 6, 2013 Mail this to a friend!
Good job Steve..I have a CD-45 that has never been used in the closet since 1990...going to bring it out this winter and mount it in a tower...
Thank you for your article and photos...

73 Tiernan
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