Raytheon ST60 Speed Transducer Problem

[Labhaoise]

Speed display stopped working one day last season all was fine cruising at 24knots when i noticed the speed dropping on the display to 0knots. I figured at the time my paddlewheel may have got fouled in the transducer.

Well it was one of those jobs i have left on the long finger till the other week. decided to investigate the problem a little. so after locating the thru hull transducer i pulled out to inspect and found no fouling and free movement of the wheel.

what now?. How will i go about testing if i have a transducer fault/wiring fault or would i have any other issues seeing that this is a ST60 system with tridata repeater. By the way same readings on the repeater.

 

[Wiggo]

This may be a daft question, but have you had someone watch the display while you spin the impeller by hand? The fact that the display dropped off rather than just vanished implies the wiring and transducer are probably sound, but that wheel may not be going round.

 

[earlybird]

Is the temperature readout showing a sensible figure? say ~10 deg C. at a guess. If not, then the thermistor in the transducer has failed and this will give the symptoms you are seeing.
If this is the case it's easy to fix with a ~10kohm resistor on the back of the instrument.
Hope that helps.

 

[Labhaoise]

This may be a daft question, but have you had someone watch the display while you spin the impeller by hand? The fact that the display dropped off rather than just vanished implies the wiring and transducer are probably sound, but that wheel may not be going round.

Had no one to look at display while spinning the wheel but can confirm it moved freely. as i am in fresh water there is no growth on the wheel. i figure that a free wheel should have no reason not to be giving a signal.

Is the temperature readout showing a sensible figure? say ~10 deg C. at a guess. If not, then the thermistor in the transducer has failed and this will give the symptoms you are seeing.
If this is the case it's easy to fix with a ~10kohm resistor on the back of the instrument.
Hope that helps.

Did not check out the temperature read out, excuse my ignorance i did not even know the transducer measured both.
i'll check this out this weekend

Thanks for this advise

 

[Labhaoise]

Is the temperature readout showing a sensible figure? say ~10 deg C. at a guess. If not, then the thermistor in the transducer has failed and this will give the symptoms you are seeing.
If this is the case it's easy to fix with a ~10kohm resistor on the back of the instrument.
Hope that helps.

On the boat today and had a check on the temperature Reading . It measured 15.8C for water temperature . I suspect that in our climate this might be a little high seeing that the average air temp has only been around 12-14c lately. Surely the fresh water would be cooler this time of year. Should I suspect that I may have this problem you mentioned?

 

[earlybird]

Can't remember what mine read except that it was wayout, so I supect yours is OK and the problem is elsewhere. The reason why a failed thermistor affects the speed reading is that it causes the ST60 to act as repeater rather than master.
If you like fiddling, there's testing info. at:- http://raymarine.custhelp.com/cgi-bin/raymarine.cfg/php/enduser/std_adp.php?p_faqid=1320&p_created=1187883817&p_sid=ovbwcZ_j&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9Nyw3JnBfcHJvZHM9OCwyNjAsMjYzJnBfY2F0cz0wJnBfcHY9My4yNjMmcF9jdj0mcF9zZWFyY2hfdHlwZT1hbnN3ZXJzLnNlYXJjaF9ubCZwX3BhZ2U9MQ**&p_li=&p_topview=1
You could try the resistor test and others.
Hope that helps