ST50+ masthead DIN socket - how’s it wired?

[KAL]

Did the bearing change on my ST50+ wind transducer and remounted. Was working beautifully, but the cockpit display now shows 0.0 kn and needle does not move when wind changes. Have swapped the transducer but exactly the same symptoms.

The wire to the socket at the masthead is quite tight and I feel it’s likely that the power feed (or one of the other 4 wires may have come adrift, so need to get back up there to repair.

Has anyone else done this aloft, and if so, can you tell me if the connections inside the DIN socket are soldered or are they push/screw fit. I know they are going to be tiny and awkward to work on up there and am not looking forward to the job, but any pointers would be welcome. I do have a gas soldering iron, but soldering and I are not the best of buddies, even on a workbench.

...or do I just cave in and get a pro to go up and do the job?

 

[earlybird]

It's a while since I played around with my MHU, but AFAIR the wire can't be easily disconnected from the socket. Isn't it moulded on?

 

[matthewriches]

Just a stab in the dark but have you done this yet? http://www.raymarine.co.uk/knowledgebase/index.cfm?view=4254

 

[KAL]

Thanks Matthew, but no. The display is in a sealed unit of four displays above the companionway and it’s a major job to breach it.

Its just too much of a coincidence that we’ve had to make 3 trips to the masthead to swap out transducers, (I’ve got two, both with new bearings and both were in full working order) only to find that the display says zero.

If I can, I will measure the voltages and see what I can find. Thanks for the info. Much appreciated.

 

[PowerSlapper]

HWMO just had to repair his MHU. The arm contains the female bits while the fitting on the MH contains 5 pins (the male bits) The repair started by metering the cables from the cockpit display unit socket to the deck plug then as these seemed ok the cable within the mast was metered for continuity (5 connections) between the mast head connection block and the deck plug. As continuity seemed ok teh deck plug connection was remade and the MHU was refitted and it worked, then it didn't, then it did, then it didn't. Display was blank or fixed or flashing or worked OK. Wriggling the MHU seemed to get it working then it would fail then it would work so went to change the MHU only to find the replacement would not go on / plug in. Closer inspection revealed one of the female "sleeves" had come away from the din style socket on the MHU and was still attached to one of the connection pins preventing the replacement unit being fitted. This "sleeve" was removed from the pin and the replacement MHU fitted - All working now. The fault seems to have been a broken "sleeve" in the MHU arm / connection block.
The connection cables in the block (pins) are moulded in and do not appear to be easily repairable however replacement block/cable assembly is available.
The other bit (on the arm) has the female sleeves but does appear to be openable and repairable

 

[KAL]

HWMO just had to repair his MHU. The arm contains the female bits while the fitting on the MH contains 5 pins (the male bits) The repair started by metering the cables from the cockpit display unit socket to the deck plug then as these seemed ok the cable within the mast was metered for continuity (5 connections) between the mast head connection block and the deck plug. As continuity seemed ok teh deck plug connection was remade and the MHU was refitted and it worked, then it didn't, then it did, then it didn't. Display was blank or fixed or flashing or worked OK. Wriggling the MHU seemed to get it working then it would fail then it would work so went to change the MHU only to find the replacement would not go on / plug in. Closer inspection revealed one of the female "sleeves" had come away from the din style socket on the MHU and was still attached to one of the connection pins preventing the replacement unit being fitted. This "sleeve" was removed from the pin and the replacement MHU fitted - All working now. The fault seems to have been a broken "sleeve" in the MHU arm / connection block.
The connection cables in the block (pins) are moulded in and do not appear to be easily repairable however replacement block/cable assembly is available.
The other bit (on the arm) has the female sleeves but does appear to be openable and repairable

Thanks all for replies.

Jules, my MH arm has male pins, but I can see how a female sleeve might become detached. As a matter of interest, how did you go about metering for continuity between such far-apart connections? My multimeter only has short (12”) wires? Am I missing something or being a bit dippy?

 

[sgr143]

View attachment Diagnosing a Problem with a Raymarine ST50 Wind Instrument.doc

I've tried to attach a document here which may help. "Diagnosing a Problem with a Raymarine ST50 Wind Instrument". I didn't write it - I forget who did, but I'm very grateful to them - and I've added a few of my own notes to it.

I've been struggling for some time with mine - I thought I had it sorted last time the mast was down but now while the windspeed is OK, the direction is all over the place. I need to take time to do a proper calibration.

I had to re-solder connections to the pins in the MHU. Very fiddly, even on a benchtop. I would reckon that doing similar to the socket while up the mast would range somewhere between "desperate" and "impossible".

To check the connections / continuity with my multimeter, I used a long piece of wire with a croc-clip at each end to extend one of the probes. I keep one in the tool kit for tracing connections around the boat.

Good luck!

Steve

 

[sgr143]

The reason I needed to service the MHU was that the clowns at a certain Cowes boatyard who had put in back in the masthead socket had shoved it in misaligned, bending and breaking the pins. I got a new part, and having soldered up the pins in the MHU, checked it out on the benchtop using a "picoscope" which lets you use a laptop as an oscilloscope. This is very useful, as it lets you see the signal from the windspeed line (downward spikes from a steady voltage, time interval between spikes decreasing with increasing windspeed) and the sinusoidal changes in the green and blue direction lines as the windvane is rotated. The direction lines only work when the anemometer is rotating, so I used a fan heater (on cold!) to generate a bit of a breeze. I have a video of this, but it looks like I can't simply upload it; screenshot attached.

 

[KAL]

Thanks a million sgr143. That’s a really useful post. I haven’t got the kit needed, but the ‘long wire with croc clip’ trick is definitely worth a go.

Jules, thanks for the info that a new block and cable is available. I’ve found it and so can replace the cable if that’s what’s at fault.

 

[FulmarJeddo]

I had similar problems. When I bought the boat, the direction vane was broken and the wind speed was intermittent. I replaced the wind vane and then nothing worked. I had tested all the voltages at the deckplug and all were as the Raymarine document. After several trips up the mast I discovered some damage to the cable that had been pushed back in to the mast at the foot by the previous owner. I discovered the screen or shield wire was broken. So although everything tested ok at the foot of the mast, had I tried to measure the voltages at the top, all the tests would have failed. A fairly easy soldiering job got it all working.

 

[KAL]

Found a very corroded shield wire coming from the MH cable in the junction box under the mast, so stripped back and remade the connection. The shield wire is quite black, so it looks as if I may need to replace the cable altogether. Will need a pro to do it. :ambivalence: