Wind Instrument Problem

[SailingMisty]

Greetings All! This is my first post on this forum. I'm trying to trace a nagging problem with the wind instrument in my Simrad IS20 suite. I installed it new three years ago and enjoyed a season of networked navigation instrumentation bliss. I tied in the Lawrence HDS Gen 2 Plotter, DST800 Transducer, Point-1 GPS Antenna, Link8 DSC Radio, IS20 Combination, IS20 Compass and IS20 Wind Instrument. Each IS20 display, the DST800 and Simard 508 Wind Transducer are each connected individually to an NMEA2000 hub which is also connected to the Point 1, DSC Radio and Lawrence Plotter. Each were talking nice with each other until I hauled Misty for the winter and unstepped the mast for cabin top work. The yard cut the network cable instead of unplugging it. After that the wind display would not show speed or direction. It would power up just like all the other displays, go through it's set up mode, but would then only display ------ across the screen and the direction needle wouldn't move. I've attempted every combination of removing other network devices and hooking just the wind instrument up. Nothing resulted in a different result. I climbed the mast and removed the Simard 508 wind transducer and hooked it up directly to the network bi-passing the network cable from the mast and it worked fine. I'm suspecting a problem with the network cable in the mast.

Has anyone else had similar problems? It is possible, although not likely, that a hardware attachment on the mast effected the cable inside. There are 5 conductors...blue, white, red, black and the shield. I tested continuity with a Fluke 322 clamp meter and the blue and white conducted tested positive...approximately 122 ohms. That could be a short between the two or it could be they are meant to be if sending data from the transducer. What else should I be checking in order to identify the problem?

Thanks in advance for your comments and guidance.

[smac999]

if the unit doesn't work on the mast, but works when pluged in down below, then your mast cable is bad. I would look at the mast bottom splice. how did they reconnect it after cutting it? I bet your issue is there.


the blue and white tested againest each other will be 120ohms from the bottom connector, (unpluged from the network) because the mast head has a 120ohm end terminaotor it in. (and should be feed into the end of the backbone, not as a drop)

with the mast head unplugged you should also see 120 on the blue and white on the network side. if you see 60, then you have an extra end terminator and it was wired as a drop instead of backbone, though likely not your issue)

to test the cable. you need to test all 5 between top and bottom. IE blue at bottom of mast to blue at top of mast. so you need 2 people and a long test wire.

check for 12v on the red and black at the splice and mast top.

those unless it's the splice it's going to be in the cable. knowing which of the 5 wires is bad doesn't really help you, you'll pulling a new one either way.

[SailingMisty]

Thanks for the quick comment and advice. I believe I have the wind instrument connected as a drop. I will switch it to an end and see if that makes a difference. I'm not sure it will since this configuration was working fine up until the mast was unstepped.

The cable was cut and then spliced to existing using a terminal strip. All 5 conductors are tied in at the strip including the shield.

[MarkSF]

"The cable was cut and then spliced to existing using a terminal strip. All 5 conductors are tied in at the strip including the shield."

I'm not sure this works very well at higher frequencies. It's possible the impedance break is causing reflections. I fear you might have to run a new cable up the mast, or install a field-installable connector at the cable ends and then connect them together.

I believe that the IS20 wind transducer includes a terminator so it should be at the end of the bus, not as a drop. It shouldn't ever have worked as an NMEA 2000 drop.

So I suspect that it only just worked, and now with the splice, it doesn't.

It might start to work, despite the splice, wired properly.

It's all in here :

http://www.chicagomarineelectronics....nstall-Man.pdf

[smac999]

terminal strips is perfectly fine for N2K, there is even info on how to wire them properly in the nmea specs to keep the hot-swapping ability of N2k.