JRC 1000 MKII scanner not rotating

[Eastsounder]

Hi -- I'm a newbie, jumping right in with a radar question ....

About a year ago, I removed my little lobster-style trawler's wooden mast (with the JRC 1000 MkII closed-array scanner mounted to it) to do some refinishing on the mast. When I remounted the mast, the scanner wouldn't rotate-- I must have knocked it out of whack. So when I turn on the display unit, it does its 60-second warmup countdown, then I press the X-MIT button to start the scanner -- I hear a bit of clicking and scraping from overhead, then nothing ... and no image shows up on the display. Sounds like it's stuck.

I've never taken the cover off the scanner before. Is that even advised? What troubleshooting steps could I take? I rarely used the radar before it stopped working, but it would be nice to have it next time I find myself in a fog or, dog forbid, running home after dark.

Any advice warmly welcomed. Thanks!
Craig

 

[N4712]

Welcome aboard! Maybe the belt pooped of the drive motor?

 

[psneeld]

I can't remember that specific model...but here's a generic "older" radar type troubleshooting...

Scanner cover comes off easy and is no big deal...I can't remember if that model has a giant O-ring gasket or not...just go slow and careful. Again I can't remember if the motor has a cover over it but there should be 1-3 small plates being held down by small Phillips head screws. They come off easily too. If you can see where the motor is and a small toothed belt...just check those before any plate removal...if the belt goes under a plate, then remove that one and one where the majority of wires from the outside cable go.

Turn on the radar and see if the motor is turning or if the belt just jumped off/broke. If they look good, then in the plate where the wires go, see if there is a heavier set of black/red wire. They should be the scanner power and you can check to see if power is getting to the scanner.

Be careful if not used to working on stuff like this as there is some high voltage in there.

 

[Eastsounder]

Thanks for the insights! I didn't even know these units were belt-driven.

So is a brief, close-up exposure to the radar's RF fields not of concern -- especially with such a low-powered unit? Sounds like exposure to high-voltage current is the bigger issue. (Not to mention dropping small bits of hardware while standing on a ladder lashed to the mast!)

 

[psneeld]

Not really...at least according to the manufacturer.

I was a factory trained install tech and I asked that question at a Furuno training session and the rep replied would would have to have your head close enough to the bar that the sweep would hit you in the face and even then it would take minutes or more of exposure.

Like all radiation..none is better but minor repairs on these 2-4kw units are safe.

 

[High Wire]

If the drive belt is broke, the scanner is not turning and the microwaves are focused in one direction only when in transmit. They may be low but not that low. You dont want to be in front of that. Would you operate a 1000 watt microwave with no front door? Of course not.
Power off, pull the dome lid off as psneeld said and you should see the problem.

 

[BobH]

Happened to me on a Raymarine scanner. I had the cover off to connect the cable. On that unit there is a string that connects between the cover and the rest of the unit. Allows you to turn the cover loose and let it hang while working on the unit. When I put the cover back on somehow the string got tangle dup in the belt and popped the belt off. Something may have gotten loose when you had the unit removed.

Bob

 

[jleonard]

I have only owned 2 radar units both Furuno and BOTH units quit working when the motor that truns the scanner froze up.
Easy fix, but not cheap as those little motors are pricey! (close to $300).

 

[Capt Kangeroo]

I had one of those years ago. Every year I had to open the radome to disconnect wiring to take the unit down for the winter. Note the scanner is normally a noisy unit and sounds like a dry bearing when running.

In addition to the good suggestions above. Remove the 3 bolts that hold the lid on and you will see the antenna (looks like a little satellite dish), this runs in circles on a track around the circumference of the lower housing. Try gently rotating it manually and have a close look. If it got banged hard taking the mast down it's possible it may have derailed. It is all very-very flimsy aluminum in there. Funny but I don't recall the belt set-up at all so it could possibly be driven directly but in any case once you get the lid off it will all be readily obvious.

 

[psneeld]

What most small dome radars look like inside...

 

[Eastsounder]

Many thanks to everyone for all the good suggestions and helpful info. I now feel confident enough to open the radar cover and have some idea of what to look for inside. With luck I'll make it to the marina today, lash my ladder to the mast, and have a look. I'll report back with findings -- and, no doubt, more questions.
Cheers all,
Craig

 

[Ski in NC]

Be safe up there!!!

 

[Eastsounder]

I managed to open my JRC radar scanner yesterday. I was expecting the "guts" of the unit to be in the bottom casing, but they were in the "lid," which I turned upside down and removed 3 small fillips screws. This freed the "guts" from the "lid," exposing the scanner array. I couldn't really see the motor inside the inner casing, but what I could see were two white nylon gears -- a smaller one that appeared attached to the motor drive shaft and a larger one attached to the scanner axle or pivot-point. No visible belt. I set the unit, now upside down (i.e., scanner array facing up) loosely on the bottom casing, climbed down to the cabin, turned on the radar, then looked up the mast to see if the scanner was rotating. Lo and behold, it was. Turned off the radar, climbed back up the mast and examined things to see if there was any obvious impediment inside the casing to free rotation. There wasn't. There was, however, that string that someone mentioned to keep the guts attached to the casing, I guess so you wouldn't drop the upper half of the unit -- although the string would only come into play if you detached the power cable, which otherwise held things together pretty tightly. Anyway, I wondered if maybe the string somehow got in the way of the rotating array. Putting everything back together, with the top half seated in the black ring-gasket around the bottom half, was the hardest part. Once I finally got it right, the darn thing worked! Not sure what I did besides take it apart and put it back together, but it appears that the problem is solved -- for now.

Thanks again, all, for all the tips and pointers. I couldn't -- or at least, probably wouldn't -- have done it without you!
-Craig

 

[psneeld]

.....................

 

[jleonard]

Once I finally got it right, the darn thing worked! Not sure what I did besides take it apart and put it back together, but it appears that the problem is solved -- for now.

Hey sometimes it's better to be lucky than good

You probably had a bad connection somewhere that you inadvertently corrected.

 

[alormaria]

You discovered one of the fundamental laws of electronics. That if you take a non-running electrical unit apart and put it together without fixing anything - it will work.

The other law is if you drop an non-working electrical unit approx. 2 feet onto a hard surface protected by a layer of corrugated cardboard - it will start to work again.