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Old 14-06-2013, 10:29   #1
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Angry ST50 Speed Problem

The Read-out marches up and down sometimes settling on the correct speed for a while. Say correct ~5kts Reading range ~2 to 25kts.

Need help with diagnosis.
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Old 14-06-2013, 11:05   #2
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Re: ST50 Speed Problem

fouling of the paddlewheel transducer?

Dave
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Old 14-06-2013, 12:21   #3
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Re: ST50 Speed Problem

Thanks dave. No. I have carried out all known checks of the system.
I assume the head can count & therefor is receiving bad pulses from the wheel -- but need more assurance before replacing.
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Old 16-06-2013, 17:57   #4
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Re: ST50 Speed Problem

Quote:
Originally Posted by Johncabot View Post
The Read-out marches up and down sometimes settling on the correct speed for a while. Say correct ~5kts Reading range ~2 to 25kts.

Need help with diagnosis.
Bunch of questions:
- how often does this occur?
- what else is happening when it occurs? (sailing conditions, fast/slow, port or starboard heel... only when generator runs, etc)
- how old is the installation? How old are the instruments?

I'm thinking it's cabling or something to do with it (eg interference). I'd suggest first inspecting all connections between the transducer and the instrument, including the lugs at the instrument. Fix anything that seems iffy, loose or corroded.
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Old 17-06-2013, 07:14   #5
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Re: ST50 Speed Problem

Thank you. The problem is at all conditions. When it settles on the correct speed it will hold for 3 or 4 minutes. The unit is ~ 19 years old.
I am scrupulous in maintenance and store the read out off the boat in Winter. I believe you are correct about connections but there is only one at the read out. Gold plated and shiny clean. I think the transducer, needs replacement but I must pull the floor up plus much more to run the cable and wish to be sure it's worth it.
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Old 17-06-2013, 07:45   #6
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Re: ST50 Speed Problem

Quote:
Originally Posted by Johncabot View Post
I believe you are correct about connections but there is only one at the read out. Gold plated and shiny clean.
How about the crimped-on connectors? Do the crimps still seem solid, any looseness or visible corrosion in the crimp area? Maybe give them all a little squeeze with a crimp tool.

if you can borrow a known-good sensor, you can verify that the instrument is ok... hold the paddle wheel under a running tap.

Longshot... If you know someone with a portable oscilloscope, using one to look at the pulses at the instrument coming from your speed sensor would tell you alot about the sensor and the wire. You should see nice fat rectangular pulses all at the same levels, no jumping about, no skinny or soft pulses, no extraneous signals.
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