Tuesday, September 3, 2013

Radar Rx

It's not op art, only a cheesy replica of a radar screen image I get to see on occasion. In reality it's pretty close to what the screen actually looks like. This image has two likely sources. If it's a reasonably clear image the array is not turning, and you're seeing an image from one direction only. If the image is noisy another possible scenario is you have a lot of condensation on the inside of the radar dome.

In this case the little domed Furuno array was not turning. Opening the dome and seeing the drive belt disconnected immediately conjured the insight that if the belt was put back in place, the array would turn, and the problem would go away. This proved to be the case, for a few seconds at any rate.

Pretty picture, oops concentric circles again. The dome gets re-opened, and I take a closer look. The belt is off again, and when I looked closely at the little DC motor drive gear, I found it was loose.


I climb down and spend five minutes locating my jack knife like metric Allen wrench set. A few minutes of monkeying around on the arch gets the little gear locked in place. The radar gets turned on and starts to paint, but not correctly. My brain succeeds in dredging up the sequence to get to the radar installation and set up menu. The wrong  radar type was selected. That's corrected with a button push. The radar and video gets tuned. All is good, and this is as easy as it ever gets. Most of the time with radar repairs I spend scratching my head.

This was an quick and empirical fix, and the easiest of the three I have dealt with the past few weeks. The next one looks bad, but in reality it will be fixable. By that I mean at least we know what is wrong, which is better than you get in most cases. This is the less than judicious meeting of a marina fork truck moving a boat, and a steel I-beam. The resulting severe damage to the unit is not pretty. So if you can't handle marine electronics damage Tarantino style look away right now.

I told you it wouldn't be pretty. It was decapitated leaving array gray matter exposed and in ruins. Knowing what is actually broken is actually a huge start in the right direction. The damage is confined to the array, and the dome cover. The drive system system is okay, and by installing a new array, and top cover the radar will survive after spending some time in rehab.

So the radar is broken, where do you start? Do a quick check of what's happening below to confirm its status, then statistics say to start with the radar unit itself. So grab your tools, and get your butt up to where ever the unit is mounted so we can check some things out.

If it's an open array, I give it a swing? Does it move smoothly, or do you hear funny noises? Noises, and or no motion, means mechanical issues at the minimum and it's now time to open it anyway. You're going to have to open the dome units from the get go.

Lack of use is the number one killer of radar units. Whenever you leave dock, turn it on, and use it. This drives out moisture, makes bearings turn, and belts whirl around. 

A good chunk of the time, corrosion is the problem. Gaskets that weren't properly seated from the last time it was opened are a common source of this issue.

Mechanical problems are generally visible and easy to track down. Broken belts, and seized bearings are the two biggies. Sometimes you can use a light machine oil on stuck bushings and bearings being careful to not let it get into the electronics, and manually work the array to free it. Sometimes if the damage is severe the drive system may need to be replaced. We'll get back to this later.

If we seem to be mechanically okay, then next we check for power. On most radars the power wiring is apparent so check for 12 or 24 volts. No power? Then cable, and or MFD/Display/fuse block become suspects.

Some radars such as Raymarine's open array units have an external on off switch. Check that this is on. You would be amazed at how easy it is for boat cleaners with that sham wow thing at the end of a stick to accidentally bump it off.

There isn't much more to do at the radar end. On older units check the data wiring. This usually consists of one or more small connectors. Put your peepers on, pull the plugs one at a time and check for corrosion or broken connections.

On newer systems such as the pictured Garmin unit disconnect the network cable and inspect it. While you still have the peepers hanging on your nose look for corrosion on any exposed circuit boards. If you haven't found any problems yet, it's time to move on.

We haven't by any means, eliminated the radar yet, but we are reaching diminishing returns with what we can do.

Checking the cable is next, to the best of our ability. The tech's often suggest you ohm the cable. It isn't that it's a bad idea, it's just such a P in the A to do. This involves two people, having two cable pin out drawings printed out, multimeter, at least thirty feet of wire, and paper clips or the ilk to stick into the small female ends of the connectors. All of these you don't have the first time you see the whatever model of radar that is broken. This is a low probability failure, but as you can see from the picture, it is a possible failure mode. But for the time being we will skip this.

Now down below there are some other things to check, and you could have done some of this at the beginning, but it really doesn't matter. Remember it doesn't work in the first case. If you had no power up top, in many cases the radar cable splits off at the bottom and the power leads go to a fuse block. If so, find it and check the power there. No power, fix it. Radar works? If so done. Have power, and radar doesn't work? It could still be the radar, cable, or MFD/display. Pull the radar cable connector from the display, inspect it, and if all looks well plug it back in, and check the system. If it still is DOA we are running out of options, and it can still be the radar, MFD/display, or cable. One last thing to try is to see if there are some diagnostics you can look at in the system. If the radar is broken, this rarely produces any usable information, other than to tell you it's broken.

This is the time I throw the pragmatic dice and play the odds. Most of the time the problem lies with the radar unit itself, or a major component inside of it. It lives outside giving it plenty of environmental exposure, and it's rarely used in most cases insuring it can quietly corrode into oblivion in privacy.

So back to the cable business. It will take about an hour minimum to get prepped and ohm the cable, so let's say it costs a hundred bucks to do it. If things are convenient, maybe less, and going up a mast a bit more. My experience with this boils down to the fact that I have had maybe three or four bad cables over the past decade. One had a screw driven into it, and one was cut while it was pulled up through a mast, so I think it's a poor bet. So at this point, or even before depending on circumstances, the radar should just get pulled, and go back to the factory for bench testing and or repair. If you want to kill two birds with one stone, send in the MFD, and or display with it. 

To be honest it's typically overall cheaper to just send both pieces to the  repair center if a cursory examination doesn't produce quick results, then to keep grinding away at a often elusive problem you most likely can't fix anyway. In the field I only have at the very best about a fifteen percent success rate of repair, and that includes some of the simple things like throwing the Ray open array switch to the on position because of sham wow syndrome. In the end they are big black boxes loaded with complex electronics that typically can't be field repaired anyway. Oh, if they come back and were tested as operational you lost the cable lottery, but I would still play those odds.

Lastly if the manufacturer doesn't support your radar anymore I'm going to provide you with a first class source who likely can fix it, and a bunch of other marine electronics also.  This will be a just a little later this week. 

7 comments:

  1. What's your opinion of packing all exposed marine connectors with silicone dielectric grease? And even wrapping them with 3M rubber self-vulcanizing tape, like their Temflex #2155 after doing so?

    PL259s on VHFs are especially vulnerable, since they have no o-rings, but I suspect lots of connectors for radars leak salt water, too, without additional protection....

    The cable, cell, and ISP industry is anal about using Temflex on tower connectors, because who wants to climb? They also use stainless cable ties, rather than plastic, again, because who wants to climb?

    Thoughts?

    ReplyDelete
  2. Thanks Karl, good questions. The radar cable pass through fittings work well if properly tightened down. The radar problems come from two areas. The first is the big gasket. Care has to be taken to make sure it's in the right place when the case is bolted together, or you can fill your radar with rain water. A larger, albeit slower problem is the heating of the day pushes some air out, and the evening cooling sucks some air in that has salt in it. The moisture then condenses on the interior. This is an inexorable process, and the reason I am always exhorting readers to run their radars above and beyond the Rule 7 requirements. The heat generated while operating will help to drive moisture out, and keep parts from freezing up.

    I haven't personally used the 3M tape product, but I have been on the receiving end of staring at a ball of rubber tape encasing a connection that has over the years in Florida's temperatures coalesced into a amorphous gooey mess.

    I have also sighed while reaching for a roll of paper towels as I stare at terminal blocks that have been coated 1/8" deep in heavy duty CRC by the infamous mad sprayer dude.

    I use Boeshield T9 in corrosion prone locations. It works well, holds up for a long time, and doesn't make a big mess. In the end, I think you just have to take things on a case by case basis looking at the potential for exposure, and use your best judement.

    That being said, there is a season and time for all of these products, you just have to remember that you will have to clean it up someday to make fresh new connections or repairs. A final note, a couple of years ago, I had a client who confused dielectric grease with conductive grease. I explained the difference as I was installing his brand new chart plotter. Bill

    ReplyDelete
  3. Thanks Karl, good questions. The radar cable pass through fittings work well if properly tightened down. The radar problems come from two areas. The first is the big gasket. Care has to be taken to make sure it's in the right place when the case is bolted together, or you can fill your radar with rain water. A larger, albeit slower problem is the heating of the day pushes some air out, and the evening cooling sucks some air in that has salt in it. The moisture then condenses on the interior. This is an inexorable process, and the reason I am always exhorting readers to run their radars above and beyond the Rule 7 requirements. The heat generated while operating will help to drive moisture out, and keep parts from freezing up.

    I haven't personally used the 3M tape product, but I have been on the receiving end of staring at a ball of rubber tape encasing a connection that has over the years in Florida's temperatures coalesced into a amorphous gooey mess.

    I have also sighed while reaching for a roll of paper towels as I stare at terminal blocks that have been coated 1/8" deep in heavy duty CRC by the infamous mad sprayer dude.

    I use Boeshield T9 in corrosion prone locations. It works well, holds up for a long time, and doesn't make a big mess. In the end, I think you just have to take things on a case by case basis looking at the potential for exposure, and use your best judement.

    That being said, there is a season and time for all of these products, you just have to remember that you will have to clean it up someday to make fresh new connections or repairs. A final note, a couple of years ago, I had a client who confused dielectric grease with conductive grease. I explained the difference as I was installing his brand new chart plotter. Bill

    ReplyDelete
  4. Hi loved this no-nonsense approach. I am one of the unfortunates who probably needs to do most of what you are talking about here. My Navman 2kw radar stopped working a while ago and I finally got up the nerve to ignore all the "WARNING RADIATION!" signs and open up the dome. It was full of water! And there was a ton of condensation all over the inside of the dome. It did not taste like seawater, so I think your suggestion that it is likely rainwater is correct. I also noticed that the top cover was NOT well (read: tightly) fitted to the rest of the dome, and it seems highly likely that is how the water got in. In fact I cant believe how flimsy the top (4 small bolts and a pretty minimalist foam rubber seal gasket) cover actually is considering the value of what it is protecting. Anyway, any thoughts on what to do? tested it again after removing water, and it is still not working. Is it cooked? Or is it possible that just, say, the drive motor is toasted (array will not turn, but I can see an image on the display - does this mean processor is still working?) Thoughts?

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  5. A common misconception is that there is salt in sea air which is wholly impossible...as we have all learned in middle school, when salt water evaporates, only distilled water is the result. If a hurricane is blowing over salt water it will indeed pick up the water and blow it on your boat...otherwise there is NO salt in sea air!!

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  6. Hi Greg, and thanks. As you mentioned there is no salt in the air caused by evaporation, but there is salt in the air. This is called sea salt aerosol. Salt in the form of small water particles ends up suspended in the air when waves break or are white capping. In coastal areas the amount of salt in the air can be significant.

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  7. Does anyone know where I can find a vertically polarized slotted waveguid x-band antenna? I'm having a lot of trouble finding any. Any help would be appreciated.

    ReplyDelete