Date sent: Sat, 2 Aug 1997 16:31:02 -0400 To: amsat-bb@amsat.org From: Ron Long Subject: G-5400-A/B Repair Reprints Notes on Yaesu Satellite Rotator Repairs from Ron Long, W8GUS This article presents reprints of articles which have appeared in previous publications and some email postings from amsat-bb which give valuable hints on the repair of Yaesu/Kenpro satellite rotators. By the way, for the newcomers, Yaesu purchased the Kenpro Company which originated the designs. The individual azimuth and elevation rotators were KR-400 and KR-500. Later came the KR-5400, the KR-5400-A/B and the KR-5600-A/B. Yaesu changed the designations to G.... For fleamarket shoppers, be aware that the KR-5400 (no suffix letter) which is occasionally found, has a control box that looks the same to the casual observer, i.e. two meters etc., but it does not have the rear DIN-8 computer connector and of course does not have any computer interface electronics. The elevation rotators, either individual or as part of the GR-5400 series, have limit switches. The azimuth rotator of the GR-5400-A/B does not have limit switches, but that of the GR-5600-A/B does. Sadly the GR-5600-A/B, to the best of my knowledge, is no longer sold in the USA. The azimuth rotator without limit switches will grind against the end stop until the thermal cutout on the motor shuts it down. Additionally the azimuth rotator of the GR-5600 has a higher load rating, although that is usually of no consequence to AMSAT folks. Contents: AMSAT-Australia Newsletter #42 KR500 Rotator Modifications/Fixes by Mark Spooner VK5AVQ AMSAT-Australia Newsletter #102, 03Oct93 KR-500 Elevation Rotator Maintenance by Bruce Henderson VK5KJ AMSAT-Australia Newsletter #140, 02Dec1996 Yaesu-Kenpro Rotators by Ulrich DG4MLO AMSAT-Australia Newsletter #141, 31Dec96 KR500 Elevation Rotator Corrosion by Geoff VK4GWC Oscar News (AMSAT-UK) # 92 December 1991 The Repair of Kenpro Rotator Potentiometers by P. Coull G4WFQ Replacement ball bearing kit by Richard G3RWL Oscar News #100 (April 1993) page 36 Modification for early Kenpro/Yaesu Type 5400/5600 Az/El Rotator Assemblies by G6ZRU Copies of email postings KR500 Rotator Modifications/Fixes - by Mark Spooner VK5AVQ AMSAT-Australia Newsletter #42 Having purchased a well-used KR500 elevation rotator, a service seemed in order. Due to its construction water WILL get into it, so it is important that the drain hole is clear and faces downwards. Disassemble the unit by removing the eight screws that hold the two half housings together, this may be easier said than done due to corrosion. (A No 3 Philips screwdriver, a solid support and plenty of muscle). Remove any scale from the bolts and holes, grease the bolts before re-assembling. Even if you go no further now, doing this much will aid future maintenance. Once the bolts are out, the two halves should pull apart, the ball bearings are held in place with clips, but even so be careful and use a tray (e.g. a metal dustbin lid). Unscrew and remove the innards, place aside on a sheet of newspaper. Gently remove the ball race retaining clip and remove the balls from both housings. Wire brush cleaning both halves and balls with turps, there may be quite a bit of corrosion in the bottom part near the drain hole. Paint the effected areas (except ball race seats), I used metal chromate primer followed by aluminium paint. Re-pack the ball race using a water resistant grease, try molybond, or alternately some sort of marine or pump grease. Flick off any scale from the mechanism with a paint brush, regreasing should not be necessary. Reassemble - join the two halves with a bead of silastic, try not to smear it, it makes painting impossible. Place a light coat of paint over the outside including the bolt heads. Primer first, and if you don't like aluminium, try one of the paving type paints (polyurethane) as a top coat, they are fairly UV resistant. It is also worth trying to waterproof the unit by providing a water run off with a bead of silastic just above the ball races. Most of the foregoing is obvious but hopefully may draw your attention to this problem. Finally despite the heavy life my unit has had very little wear was noticeable. 73's Mark ------------------------------------------------------------------------------ KR-500 Elevation Rotator Maintenance by Bruce Henderson VK5KJ AMSAT-Australia Newsletter #102 Recently I completely dismantled my satellite antennae system for periodic maintenance and painting. Part of this maintenance was to disassemble and service the elevation rotator. An article on the subject published in AMSAT-Australia Newsletter #42 was studied to obtain some knowledge of the procedure before the task was commenced. Let me say at this point that this particular rotator has been in use for approximately 10 years and that this would be the first time that it had been disassembled. The two halves of the rotator body are secured by eight 6x1.0mm stainless steel Phillips button head housing screws (four from each side). The screws were set fast by corrosion of the threads in the casting caused by the ingress of moisture into the threads. To remove these screws some gentle persuasion was required. The rotator was secured in a vice fitted with soft jaws with one half of the housing uppermost. The correct size Phillips screwdriver was located in the screw head recess and the handle of the screwdriver was struck sharply with a soft faced hammer (use a piece of wood in lieu). This process was repeated until the four screws yielded. The rotator was reoriented 180 degrees and the process was repeated until the remaining four screws had yielded. One screw was so tight that it was necessary to fasten a set of vice grips to the shaft of the screwdriver for extra leverage. These screws were then removed together with the two screws securing the motor assembly which then allowed separation of the housing. The tube gear assembly on the boom shaft tube is released when the "C" ring is removed. A thorough inspection of the components revealed corrosion in the screw threads in the castings, the lower internal face of the housing and the internal surface of the boom shaft tube. The rubber terminal sheet behind the terminal block had deteriorated and slight rusting of the ball bearing holder was evident. The motor, gears and wiring were in a serviceable condition. In addition the four boom clamps which were lightly cadmium plated had begun to rust. How do we restore the rotator? All internal screw threads were cleaned using the correct size thread cutting tap and the aluminium oxide corrosion was removed from the external screw threads using a wire brush. Close examination of the corrosion inside the housing revealed that the surface was pitted so cleaning the surface by scraping or with emery paper would be next to useless. After consulting several metal finishers I settled for bead blasting and anodising of the housing and boom shaft tube. The surface was then sprayed with a two part polyurethane primer and top coat. NB: ENSURE THAT THE TWO BEARING SURFACES IN THE HOUSING AND ON THE BOOM SHAFT TUBE ARE MASKED PRIOR TO PAINTING. ALSO MASK THE SECTION OF THE BOOM SHAFT TUBE WHERE THE TUBE GEAR ASSEMBLY IS LOCATED. The total cost was A$75, expensive but bullet proof. A less expensive alternative is bead blasting, priming with Wattlyl Superetch and a top coat of Kilrust Exterior Enamel (Both available in Pressure Pack). NB: WATTLY HAVE RECOMMENDED THIS COMBINATION OF PRIMER AND TOP COAT AND ADVISE THAT THE TOP COAT LIFE WOULD BE ABOUT FIVE YEARS. The four boom clamps were hot dip galvanised for additional cost of A$10. The ball bearing holder was cleaned with fine emery paper and a new rubber terminal sheet was cut from neoprene rubber sheet. Paint was removed from the internal screw threads prior to assembly using the correct size metric thread cutting taps. Reassembly of the unit is not difficult. However, two modifications are recommended. The threaded section of all screws should be coated with grease prior to reassembly. I used Shell Superplant M grease which I use on my cement mixer. It is Molybdenum Disulfide based and waterproof. Also a light smear of silastic should be applied to the mating surfaces of the housing. I would suggest that prior to installing a new rotator that the main assembly screws be removed and greased. This article should be read in conjunction with Mark Spooner VK5AVQ's article in Newsletter #42. ------------------------------------------------------------------------------ Yaesu-Kenpro-Rotators - Ulrich DG4MLO AMSAT-Australia Newsletter #140, Dec 96 Reproduced with permission of VK5AGR, Newsletter Editor Alerted by the KR-500 experiences that Kurt (DL1CR) reported a short while ago, I replaced my KR-5400 rotators during the last couple of days, (because winter approaches) with a new KR-5600. Both, the KR-500 & the KR-400 performed reasonably well for the last 3 years. Therefore, I actually did not expect any problem when opening the housing of the KR-500. Turning the 8 screws is a challenge already ! It requires, besides the proper tools, some extra muscles... I found 50% of the balls (including the entire cage) on the side facing West totally rusty, even still being covered with the original (black) grease ! The bearing on the other side did not look as bad, but also the cage showed rusty spots as well. (One ball had become lose and was found in the housing). I removed ALL of the original grease and replaced all balls (2 x 25) with rustproof ones. I also did not utilise the cages anymore, because I figure they are not serving their purpose anyway. The grease I used has a lubricating range of -30C to +130C. To be on the safe side, I enlarged the hole on the housings bottom to 4 mm to provide for better water drainage, if needed. The brand new KR-500 underwent the same preventative modification before being put up. In order to prevent rain/water from entering the housing of the KR-500, I engineered a cover, made out of aluminium and sheet rubber. The aluminium covering the top, with the rubber flaps hanging down on all four sides. The fibreglass boom sticks through holes cut in the flaps on both sides. The KR-500 (and its vulnerable bearings) is therefore completely protected from environmental hazards. I just wanted to let you know, that even after such a short period of time (3 years), the damage to the KR-500 can already be severe. For those of you who like to play it safe, I would recommend to grab the next opportunity (maybe spring cleaning....) and take preventive actions. It ís certainly worthwhile! By the way, the condition of the KR-400 did not call for similar actions, but I replaced the original (black) grease anyway since I had the housing open. ------------------------------------------------------------------------------ KR-500 Elevation Rotator Corrosion - Geoff VK4GWC AMSAT-Australia Newsletter #141, Dec 96? Reproduced with permission of VK5AGR, Newsletter Editor I disagree with most of the conclusions made by Ulrich in last month's newsletter on this subject based on 35 years in mechanical engineering. 13% chromium steel bearings would be the most suitable for bearing replacement in the rotator. Cages ARE indispensable for several reasons, not the least being that they hold the ball bearings in place. The mechanism of entry of water into the rotator is not by direct intrusion of water. Water enters by diurnal breathing of moist air and subsequent condensation. This is a cumulative process. The KR-500 has 2 small holes in the bottom which easily block and allow water to build up and prevent drying out during the day. The drilling of several larger holes in the bottom is therefore vital to preventing water build up and accelerated corrosion which result from the constant presence of moisture. The grease is black because it contains a black material, viz. Molybdenum disulfide. It is premium-grade grease but an ideal choice in this application. For corrosion protection neither moly-grease or a grease with a high temperature range is best. However, mixing the 2 types is NOT recommended. It is a pity that the manufacturer did not use more internal corrosion resistance such as painting, plating, and materials like stainless steel, brass and bronze. ------------------------------------------------------------------------------ Oscar News (AMSAT-UK) # 92 December 1991 The Repair of Kenpro Rotator Potentiometers by P. Coull G4WFQ The most popular rotators for satellite use appear to be the Kenpro or Yaesu as they are now called. In fact, I don't know of any other elevation rotator commonly available other than the KR-500/G-500. The following applies to other Kenpro/Yaesu models. The G-400, G-400RC and the G-500 all use a potentiometer within the rotator, driven via some gearing, for the directional readout. The 400 and 500 simply use the resistance as a potential divider and measure the voltage to drive a meter. The 400RC is slightly more complex, but the same principle applies. Incidentally, the 400RC also uses a similar potentiometer in the control box with the two potentiometers working as a servo system. I obtained my KR-400RC second hand, at a very reasonable price, mainly because the "control unit was bust". It transpired that the only problem was a faulty positioning potentiometer within the rotator. Inquiring of the importer for a unit, I was staggered to find the was almost 15 Pounds. Not knowing any better, I replaced same and installed the rotator, happy I had saved myself some money. I subsequently found that I could have saved even more money, simply by repairing the potentiometer! Most of the following is attributable to Rex, G4JUJ, who I thank for his help. The most common problem exhibits itself as "jumps" in the direction meter. This is evidenced by a dirty slider, causing the resistance to go high or open circuit. Sometimes the slider part breaks off, giving erratic indication, or non at all. Most problems can be cured simply by removing the potentiometer and disassembling and performing maintenance on same. Taking the potentiometer apart is relatively simple, if a bit fiddly. The metal cover is held in two places where the cover has been bent into two indentations on the plastic part. Using a small, strong screwdriver just bend the casing out again, and pry off the cover. The cover can be a very close fit, so you may need to use another screwdriver to pry it off. Once the cover is removed, the workings are revealed. To dismantle the potentiometer, you need to remove the "C-clip". If you look closely at the spindle, where it goes into the threaded bushing, you will see a small "C-clip". You will need to remove this with a small jeweler's screwdriver or a small pair of long-nosed pliers. It can be very fiddly. I assure you it will come out. With the "C-clip" removed, the whole spindle assembly can be lifted clear. You can now see if the unit needs repair, or simply cleaning. Use switch cleaner and a cotton bud to clean the parts. Make sure that both the rotor and stator contacts are well tensioned before you reassemble. I recommend you fill the unit with silicone grease. I do mean FILL. Make sure you put in as much grease as possible. This stops the ingress of any moisture and prevents any dirt ingress or corrosion. If the sliders are correctly tensioned, they will simply cut through the grease and make good contact with the stator part. When the potentiometers were originally assembled, a small "dob" of silicone grease was applied, and it is usually this that ends up attracting dirt and causing the erratic operation! Oscar News Editorial Note: If you find the winding at either end of the potentiometer broken, just unwind a turn of wire and solder or twist this onto the end contact. The lost of a small amount of resistance will not make any difference to the working of the control unit. It is also very easy to rewind the flat resistance strip with Nichrome wire. ------------------------------------------------------------------------------ Replacement Ball Bearing Kit by Richard Limebear G3RWL In Oscar News February 1991, Number 87, page 36, Richard mentions a stainless steel ball race replacement kit for the KR-400. Consists of 132 stainless steel balls and two cages to fit. Oscar News #100 (April 1993) page 36 Modification for early Kenpro/Yaesu Type 5400/5600 Az/El Rotator Assemblies by G6ZRU ------------------------------------------------------------------------------ Date: Mon, 26 Jun 95 15:24:40 +0500 (GMT) Message-Id: <9506261524.AA01528@ve4gat.ampr.org> From: ve4gat@ve4gat.ampr.org (Chris Setla) Reply-To: ve4gat@ve4gat.ampr.org To: amsat-bb@AMSAT.Org Subject: Re: Winterizing Rotors > Here in Minnesota, we have one of the widest temp swings in the US >(typically +95 to -30 F in 12 months). Here is what I did. > Go to an outboard motor / sport boat shop and get a tube of LUBRIPLATE. > Mine is White with blue and green printing, I think. It is used to lubricate > the lower powertrain of these motors. For everyone's info there is also "Lubriplate Low Temp" grease available. This grease works very well here on my rotators. I sat up one night til about 2am waiting for the temps to drop below -40c and both the elevation and az rotators ran just like it was summer time. I did strip both rotators down completly and cleaned them before relubing. I have since had the elevation rotator apart to replace a failed potentiometer and after a summers worth of heat. 73 de Chris (VE4SET/VE4GAT) ------------------------------------------------------------------------------ Date: Tue, 27 Jun 95 22:03:00 UTC To: amsat-bb@AMSAT.Org Subject: Ball Bearings. X-Genie-Id: 6958585 X-Genie-From: G.SCHRICK Taking care of your Rotor. Ball bearings do not need any grease or oil to function. They are, however, usually embedded in grease AND a protective cover. Both designed for the purpose of keeping dirt particles out and also moisture. The steel balls do rust easily! The rotors in question are good water traps. So there is plenty of opportunity for the balls to rust. This will make turning eventually too hard. Of course cold temperaturs and stiff grease does contribute. The first step with a new rotor is to put a few decent drain holes in the bottom of the case and some small ones in the side (for venting). If some damage (rusting) has occurred, the rotor should be taken apart and the balls replaced. A package of suitable balls runs about $5.-. Of course you still need the grease also. (see above) I have a handout describing the method and will mail it for an SASE. 73, GERD, WB8IFM in Dayton ------------------------------------------------------------------------------ Date: Mon, 25 Sep 95 13:41:21 CST From: "william parmley" Message-Id: <9508258120.AA812065074@SMTPGATE.ANL.GOV> To: amsat-bb@amsat.org Subject: Kenpro KR-500/Yaesu G-500 Elevation Rotators LUBRICATION OF THE KENPRO KR-500 ELEVATION ROTATOR ABSTRACT: This report describes disassembly, lubrication, and reassembly of the Kenpro KR-500 elevation rotator. It has been noted by others that the Yaesu G-500 elevation rotator is identical to the Kenpro, except that the Yaesu incorporates end-of-travel limit switches. The Kenpro KR-500 design incorporates semi-caged ball bearings and an integral motor/gearbox assembly, making it unlikely that the unwary technician will be greeted by a lapful of loose bearings and/or gears upon separation of the case halves. (Loose ball bearings can be dealt with. Loose gears may be an indication of big problems.) EQUIPMENT REQUIRED: - Impact Screwdriver (probably) - Hacksaw (maybe) - Phillips Screwdriver - Flat-blade Screwdriver (small) - Vice Grips (likely) - Indelible Marker - Grease (I used Low-temperature Lubriplate) - Anti-seize compound (I used Permatex brand) - Gasket compound (I used Permatex #2) - Mineral Spirits, Rags, Paper Towel, etc. - New Screws (If the old ones are rusted or damaged) - New Ball Bearings (Depending on condition) HISTORY: I was given a used KR-500 rotator last year and installed it during a warm spell at the end of winter. Once cold weather returned I found that the rotator would not turn when the temperature was below 20 degrees F. I suspected this problem was related to the type and/or age of the grease used in the rotator. The rotator operated flawlessly throughout the spring and summer, but with the return of cool weather I realized that I could not put off addressing the problem much longer. PROCEDURE: Prior to disassembly I positioned the rotator to zero degrees elevation, removed the antennas and cross boom, disconnected the control cable, then removed the rotator from the mast. I began the disassembly by first marking the position of the through-tube relative to both of the case halves with an indelible marker. The eight screws holding the casing together were rusted and galled in place, so it was necessary to use an impact screwdriver to loosen them. Two of the screw heads stripped out, so a hacksaw was used to cut a slot to facilitate removal. The two case halves were separated. The half without the terminal block was first lifted free. There are 20 ball bearings per case half, contained in a split-ring stainless steel cage made of material that looks somewhat like finger stock. The cage was separated at the split and pulled out of the opening and the balls were placed in a container for subsequent cleaning. Old sealant was cleaned from the mating surfaces of the case halves. The through-tube is fitted with a ring gear which meshes with the gearbox and can not be pulled free until the motor/gearbox assembly is removed. The motor/gearbox assembly is fastened into the case half with four screws. I first removed the two screws holding the terminal block in place, slipped off the terminal block gasket, and pushed the terminal block into the case half. The four screws holding the motor/gearbox assembly were too stiff to turn unaided, and too deeply recessed to access with the impact screwdriver. I clamped a pair of Vice Grips to the screwdriver shaft for additional leverage and found this was adequate to break the screws loose without damage to the heads. I then lifted the motor/gearbox assembly and through-tube from the case half. The bearings were removed from the case half as described above. The old grease was cleaned from the bearings, cages, and races using mineral spirits, then the parts were set aside to dry. (Use caution so as not to obliterate your alignment markings.) The old grease was carefully flushed from the gears using mineral spirits in a small squeeze bottle. Care was taken to not get spirits into the motor or position indicating potentiometer. Rags, paper towel, and Q-tips were used as necessary to remove the grease. At this point it was noted that several of the balls were rusted. I opted not to replace them at this time, although I may do so later. (Individual balls are available from a local industrial supply house.) The gears were greased using Low-temperature Lubriplate from a 10 oz. squeeze tube. (Don't forget the ring gear on the through-tube.) I worked the grease into the gears using a small screwdriver blade. (Use care not to turn the gears too much and upset the zero setting.) I squeezed a liberal amount of the same grease onto the races in each case half, placed 20 balls into each race, then slipped the cages in place. It was necessary to work the balls around the race as I inserted the cage to get them to fit between the "fingers." I then worked an additional amount of grease into the assembled bearings. On one of the two cages the fingers appeared to be sprung outward so that the balls were not held in place adequately, and the cage rubbed on the through-tube half of the bearing race. I was able to bend the fingers back into shape by carefully pushing on them with a small screwdriver blade. I reinserted the motor/gearbox assembly and through tube into the proper case half (paying attention to my alignment marks) and pulled the terminal block out through the opening. I coated the threads of the four screws with anti-seize compound and fastened the motor/gearbox assembly in place, then reinstalled the terminal block and associated gasket. I coated the mating surface of one of the case halves with Permatex #2 gasket compound, let it dry a few minutes, and fitted the two halves together. I assembled the case with new screws and lock washers, first coating the threads with anti-seize compound. (Exact replacement screws and lock washers were obtained from a local hardware store. They are metric -- sorry, I don't recall the size. 6mm, I think.) The rotator was reinstalled on the mast, the cross boom and antennas were put back in place, the control cable reconnected, and the position indication rechecked for accuracy. The entire procedure required about eight hours to complete, including removing and reinstalling the antennas. Having done it once, I think I could do it again in about half the time. All that remains now is to wait for winter to test my new grease! 73 de KR8L, DN43al, AMSAT #8735 ------------------------------------------------------------------------------ Date: Thu, 28 Sep 1995 18:18:30 GMT From: Richard@g3rwl.demon.co.uk (Richard W L Limebear) Reply-To: Richard@g3rwl.demon.co.uk Message-Id: <793@g3rwl.demon.co.uk> To: kr8l@amsat.org.amsat-bb@amsat.org Subject: Re: KR-500 etc Hi. My experience may also be useful to folks even though we don't usually get such low temperatures in southern England. > At this point it was noticed that several of the balls were rusted. You're lucky ! When I took mine to pieces a couple of years ago *most* of them were rusted. My conclusion was that they were NOT stainless steel. I replaced all the balls with stainless steel ones along with a good quality, low- temperature, silicon grease. (Local store wouldn't sell the balls in less than 50-off quantity anyway.) 73 Richard W L Limebear G3RWL g3rwl@amsat.org ------------------------------------------------------------------------------ Date: Fri, 01 Aug 1997 17:10:13 -0400 To: jeff@jehosophat.com From: Pat Kilroy Subject: Re: 5400B Service? Cc: AMSAT Mail List Mime-Version: 1.0 At 01:24 PM 8/1/97 -0500, jeff@jehosophat.com wrote: >Any suggestions for a place to have the 5400B rotor serviced? Jeff, if you are slightly mechanically inclined you can do it yourself. You might want to look into it. Yaesu in California will help you with parts and exploded diagrams. Use low temp grease when you rebuild it if you are in the cooler climate. I rebuilt one of the WA3NAN az and el sets and beheld the beauty of the 5400B simplicity. Otherwise check http://www.rotordoc.com/ and other similar service shops. 73 de Pat WD8LAQ