raymarine c120 classic intermittent "no data source"

[skipgundlach]

We have the last of the analog radars in the 24 mile version, connected to our C120 Classic. In prep for a passage, we powered up the MFD, and tested the radar.

"No data source" error...

As the R&R from the Scanmar housing is a royal PITA, we attempt to avoid doing it unless necessary. However, troubleshooting suggested I start here rather than go up the mast.

A simple R&R of the cable seemed to fix the issue. We'd recently pulled all electronics and dosed each collection with some Corrosion Block, trusting that any maybe-wonky connections would be better for the effort.

So, FF a couple of weeks, and we do another check. Same error. Dang. Can't do anything right then, so don't. FF to today, power up, and it's OK.

Not so fast, Bucko; after starting and displaying just fine, here's another error message. That remained despite several on-off sequences both before turning off the MFD, and full power-up/down cycles.

Another source I'd read with the same issue had found that it seemed to come up after a period of power up, so I tried that. No luck. Another connection remove/replace didn't result in it working.

Next step was to check the presumed power pins (4 of them). Good voltage (13.4) at both pairs. Extension cable of the installer, despite being a relatively long run, had been a 2-conductor which would only work when the engine was running and the alternator was putting out a higher voltage. Finally convinced him that your specs requiring the 4c cable at those lengths was correct, and when it was swapped, it worked.

So, what's the next step? Intermittently (not much of the time) working, all power apparently working, but no data, usually.

Thanks.

[Pitchondesign]

Two things come to mind. First, running the radar diagnostics will show more detail as to the specific error. A "no radar signal" can have many different causes. Knowing more about the error will help. Second, the connector at the raydome is fragile, and the wires are very small. It is easy to damage both the connector and associated wires, and difficult to detect when broken. Years ago, that connector was available on ebay, don't know if its still around. Another common failure is the belt turning the antenna. The belt is just an 4" O ring. Those are the issues I had with mine.

FWIW

[skipgundlach]

Update:


I had an extended conversation with a technician in UK; he turned me on to https://forum.raymarine.com/showthread.php?tid=153, and we reviewed the various possibilities.

Starting with the first post, and now this resistance measurement, I found:
1/2 46.6/7K

12/13 9.45K +/- 0.02

4/7 9.41K

6/10 116.5 +/- 0.3

I don't know whether these are within tolerance, or indicate something else.

However, none are either open or short-circuit.

Where do I go from here?