JRC 1500 NOISE

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From: Alma's Only (Original Message) Sent: 3/5/2003 11:45 AM
I'm getting ready to install a new JRC 1500 radar, which has gotten good reviews on CDory sites. However, when transmitting, this thing is really noisy. Sounds like bearings ready to throw, occasional metal scraping, "loping" noises which come and go, etc. Less noise than on the previous unit, which I returned to the supplier, but still, very distracting. And, wonder how long the unit will last.

Held the phone up to the unit while talking with JRC tech support, and they said that the motors in these result in a lot of noise like what I am experiencing. Does seem like there's a lot of play between the two nylon gears.

What experience have others had? Any adjustments which can be made?

From: Mike Sent: 3/5/2003 6:28 PM
I doubt I can help you figure this one out, but it doesn't sound right to me (no pun intended). I only know for sure of one other guy on the sites who ran a JRC, and I don't really know how to get in touch with him.

Nylon gears should be very quiet running, that's for sure. And the metal scraping sounds ominous. There may be a clue in what you term "loping" though, if it means what first came to mind. It would be a good idea to check your voltage to the motor that spins the thing as close as you can to the motor itself. If somewhere along the path is a poor connection, or inadequately sized feed wire, the voltage reaching the motor may be considerably less than battery voltage. That can make a DC motor fit my interpretation of "loping", especially if the rotational load varies. (Like running windshield wipers with a low battery - your can hear and see the motor get close to stall when the wipers reverse direction.) That's just a thought, and it is simple and free to check. You should also see if the voltage remains constant, or drops some at the instant of the noise.

Although I don't know a thing about radar mechanics, the problems you describe could also be due to an uneven mount which is forcing rotating components out of line. It would be more pronounced if the bearings are sleeve type or bushings, but can also cause even good quality antifriction bearings to make some interesting racket. Misalignment from a tweaked case can also cause moving parts to contact stationary parts and cause your scraping sound. Again, I don't have a clue as to how the unit is built, but it should be a simple check to loosen the mounting fasteners a tad and see if the sound changes. You can even leave the voltmeter hooked up while you do this to see if the voltage comes up a hair indicating less work being done to run the unit.

I sure hope you get this one figured out. It would seen to me that turning the gizmo inside the dome should be effortless for the motor, and should produce little more than a hum or whirring sound. Please keep us posted as to your progress.

Mike

From: Da_Nag™ Sent: 3/5/2003 6:42 PM
I've got the same unit. You can hear a little ka-chunk on startup/shutdown, but just a slight hum while running. Nothing sounds like what you are describing, and I can't hear the hum over the engine.

One thought - how do you have yours mounted? Mine's on a 6" Power Tower - perhaps yours is mounted directly to the cabin top? I'd think this might transfer more noise.

Bill

From: Mike Sent: 3/5/2003 6:51 PM
Oh cool, now I know of two guys with JRC's. Sorry Bill, I was thinking yours was some other critter.

From: riverrat Sent: 3/6/2003 8:04 AM
Guys:
The noisy dome is an indication of interference between dish turning inside dome & fixed base. The "loping" is the DC motor slowing down because of the drag. We see this on Lake Superior Boats once in a while. I'm guessing if the JRC 1500 is new, it got dropped during shipment or something. If not, spindle (vertical shaft) inside may be bent or worn. It is definitely repairable, but should be done by a JRC authorized service center. The dome should be almost noiseless when operating. The Lake Superior boats running JRC sometimes suffer from impact damage due to pounding (the Big Lake gets very rough), or if the dome is left outside in winter, ice can get inside & bend the spindle even though it is theoretically waterproof. JRC are good radars, but they are not Raytheon or Furuno grde stuff.

Regards
Riverrat on Chinook

From: riverrat Sent: 3/6/2003 11:51 AM
Ref. JRC 1500 Noise

I'm thinking the noise from the dome is similar tosomething I've seen twice on Lake Superior Charter Boats - some impact has slightly bent the spindle inside the dome that the dish turns on, and it is dragging as it rotates. This could also explain the loping, whcih is the d.c. rotate motor slowing down one or more times per dish revolution due to friction. I would say the package got dropped in shipment if it is new. Probably needs attention at a JRC authorized service center.

Regards,

Riverrat on Chinook

From: Alma's Only Sent: 3/6/2003 7:04 PM
Thanks for the suggestions. Da Nag, after hearing that your unit only had a slight hum while running, I persisted with JRC tech support, and got someone who was really helpful. Pretty much fixed the problem, which was attributable to the nylon gears. Below is a write-up of my contact and followup with them, in case anyone else encounters the same situation.


JRC 1500 NOISE REDUCTION

SOURCE OF NOISE: The noise appears to have originated from several problems with the nylon gears. There are two gears. The smaller is mounted on the motor shaft, and is the drive gear. The other, larger, gear is mounted around the base shaft of the rotating antenna, and is powered by the drive gear.

The problems were lubrication, engagement, and gear defect.

LUBRICATION: According to JRC, the yellow colored lubricant which the factory applies to the gear teeth hardens, and should be removed if problems are being encountered. As with all other things, it’s best not to fix problems which don’t exist. So, unless your antenna is making noise or has other symptoms which could be attributed to the gears, don’t’ worry about the factory lubricant.

Otherwise, remove the lubricant with rubbing alcohol and a clean tooth brush. I suggest you make a newspaper bib under the rotating antenna so that debris and alcohol can’t get down into the unit. Use 3-4 sheets. Also, make a loose newspaper tent for the rotating antenna, since alcohol tends to spray. Although the drive gear could be cleaned in place, I removed the c-retaining clip from the top of the drive shaft, pulled the gear up, and cleaned it over a bowl with alcohol and a toothbrush. I then cleaned the main gear in-place, with the same method.

At this point, you should have clean gears, which you can reassemble, and operate without further lubricant. If lubricant is necessary or desired (gear set differences and owner preferences), JRC recommended Lubriplate (sp?), a fishing reel lubricant available in sporting goods stores.

ENGAGEMENT: There was considerable free-play in my gears. I could hold one in place, and rotate the other back and forth enough to make noise. Don’t force this: the effect is very easy to see. JRC said that although the engagement is not adjustable, per se, it can be adjusted by loosening the small mounting nuts holding the drive motor to the mounting plate, pushing the motor forward with your fingers, and retightening the nuts. The nuts are REALLY small, so you’ll probably have to buy a wrench, unless you have ignition tools. The nuts are secured with some Lock-Tite like product. Once the nuts were loose, I had to give the motor a push with my thumb, while retightening the nuts. Expect I was just pushing the four mounting screws toward one side of the holes in the aluminum base, through which they pass. At any rate, I was able to move the drive motor enough to take out most of the excess slack.

JVC said clear fingernail polish on top of the drive motor nuts would keep them in place just fine.

I put the small nylon drive gear and c-clip back in place, powered the unit up, and it was LOTS quieter, without any lubrication

GEAR DEFECT: Even after removing the factory lubricant and adjusting the slack in the gears, I still have a very slight noise each time the antenna rotates, at the same point in the rotation. JRC says this probably a slight defect in one of the teeth on the larger gear, and is sending a replacement set. However, they also recommend trying to remove the defect myself, which I’ll do. The technique is to sharpen one edge of a popsicle stick, so that you have a wedge shape, and then run the stick between each of the teeth. According to JRC, this will remove nylon burrs, and debris which you sometimes can’t see. I’ll document whether that approach removes the noise which is consistent with antenna rotation. However, this noise is very minor, and the unit sounds fine.

As an aside, JRC recommended stuffing the core of the radar mount with rags to dampen any normal operating sounds. The unit runs so quiet now that I don't think this is necessary, but if so, will probably use loose, Styrofoam packing peanuts.