ST60 Log not working

[ifoxwell]

Hi all
Our log doesn't work, the head unit appears fine as it shows SOG.
Are there any obvious things to look at that I might have missed, is there an easy way to test the transducer etc
And assuming it is faulty, and assuming the cable is good, is it practical to cut the cable at the transducer and splice in a new one at the transducer end? Re-running the cable would be a real pain
Thanks
Ian

 

[jdc]

Test the temperature sender, which is a 10k NTC thermistor between the brown and white wires.

If the thermistor is broken the ST 60 assumes it's a repeater and reads zero knots. I have simply put a fixed 22k resistor on the ST 60 which now reads 8°C and the log has started working again.

 

[AngusMcDoon]

Failed electronics is more often than not poor connections. Get to the back of the head unit and redo or clean the connections of the incoming cable from the transducer.

 

[jwilson]

Test the temperature sender, which is a 10k NTC thermistor between the brown and white wires.

If the thermistor is broken the ST 60 assumes it's a repeater and reads zero knots. I have simply put a fixed 22k resistor on the ST 60 which now reads 8°C and the log has started working again.

There are probably more ST60 Tridatas in use with resistors across the temperature terminals than ones without. Despite having had a 10Kohm resistor there for ten years giving a fixed 27 degree water temperature reading , my 15 year old ST60 log has recently stopped working again. The resistor appears fine and I have tested with a different Tridata unit, so I have reluctantly ordered a new paddlewheel unit. I don't mind the cost of that, the nuisance is dismantling half the boat to get the wire back to the Tridata at the helm.

 

[wazza]

My ST60 doesn’t show the correct temp but as long as the wheel is not clogged which is often the case it works fine.

 

[jdc]

My ST60 doesn’t show the correct temp but as long as the wheel is not clogged which is often the case it works fine.

That was my case also for a while, but eventually it read -47°C and at that point the speed was no longer output. The resistance of the thermistor was 2.6k at that point. So checking the temp reading is worthwhile.

 

[laika]

Are there any obvious things to look at that I might have missed, is there an easy way to test the transducer etc

Apologies for stating the *really* obvious but have you eliminated the obvious mechanical things, ie extracted the log and confirmed that the paddle wheel spins freely but no speed through the water figure is registered when you spin it?

 

[wazza]

That was my case also for a while, but eventually it read -47°C and at that point the speed was no longer output. The resistance of the thermistor was 2.6k at that point. So checking the temp reading is worthwhile.

Yes I have the same silly -° but what do you mean by The resistance of the thermistor was 2.6k at that point. Seems like I don’t understand.

 

[jdc]

I put a DVM on resistance scale across the brown and white leads, having first disconnected them from the back of the instrument, and it read a low resistance value of only 2.6k Ohms. It should read about 10k Ohms at 27 °C and maybe 20k at 10, so 2.6k is an unrealistic value, indicating a faulty temperature sensor.

 

[dolabriform]

Hi all
Our log doesn't work, the head unit appears fine as it shows SOG.
Are there any obvious things to look at that I might have missed, is there an easy way to test the transducer etc
And assuming it is faulty, and assuming the cable is good, is it practical to cut the cable at the transducer and splice in a new one at the transducer end? Re-running the cable would be a real pain
Thanks
Ian

Hi Ian

As others have said, test it spins ok. Test the resistance on the temperature sender wires. Check the connections on the back of it.

If all the above is ok, then you could try a factory reset of the display.

If it turns out that the log is faulty then splicing in a new one will be fine.

David

 

[PaulRainbow]

There are probably more ST60 Tridatas in use with resistors across the temperature terminals than ones without. Despite having had a 10Kohm resistor there for ten years giving a fixed 27 degree water temperature reading , my 15 year old ST60 log has recently stopped working again. The resistor appears fine and I have tested with a different Tridata unit, so I have reluctantly ordered a new paddlewheel unit. I don't mind the cost of that, the nuisance is dismantling half the boat to get the wire back to the Tridata at the helm.

You can cut and splice the cable near the transducer, or anywhere convenient, no need to re-run the whole cable.

 

[Graham_Wright]

A log does not measure SOG. It measures speed through the water. Are you confusing the information with GPS derived speed?

 

[RichardS]

A log does not measure SOG. It measures speed through the water. Are you confusing the information with GPS derived speed?

I assume that the display will show SOG derived from the GPS but not STW from the paddlewheel.

Richard

 

[MagicalArmchair]

My ST60 log has never worked - even when launched with a nice clean bottom. I wonder if this is the issue? Has anyone ever written up installing the resistor?

 

[jdc]

... has anyone ever written up installing the resistor?

I'm going the boat tomorrow, so I'll take a few photos and post them.

 

[ithet]

Has anyone ever written up installing the resistor?

See this thread from post #13:
Raymarine ST60 Tridata wrong temperature

 

[Slowboat35]

Does this resistor dodge work on other raymarine instruments or is it restricted to the ST60?

 

[MagicalArmchair]

I'm going the boat tomorrow, so I'll take a few photos and post them.

Thank you, and thanks everyone else also. It would be nice to mark another job complete (and system working) on board.

 

[ifoxwell]

Thanks for all the replies guys, sorry i've been away from the PC so I'm only now catching back up.

To answer a few questions. Yes the log is clean and spins freely. Yes I have checked the connections to the head unit and everything is clean and corrosion free. And yes it reads SOG so i can be confident that the display is functioning ok just not getting a signal for whatever reason from the log.

I'll follow the link for the resistor idea next, thank you for who ever sent that and JDC I would be interested to see how it was implemented on your boat.

Cheers everyone

Ian

 

[jdc]

Here are some pictures from today.

The log didn't work all last season, and the temperature has read a funny value: +48.7˚C on SPEED log,



and -2.5˚C on the repeater in the cabin. Neither seem right!


So the DVM on kOhms across the brown and white leads


shows an implausible value (2.24k today, it was 2.6k last week when ambient temp was around freezing).
Here is the relationship between resistance and temperature that it should have (it was around 10˚C today).


So I found an old resistor hanging around in the electrical spares box: 22kOhms (red red orange).
Should read a bit under 10C, perfect! Attach a couple of 2.8mm spades,


cover with flexible heat-shrink, with some silicone goop inside it.


And push it in place of the brown and white wires (which I have folded out of the way).
I was perhaps a bit mean on the length of the wires to the resistor, and an inch or two longer would have been easier to fit.
No need to use any particular value of resistor, anywhere from 8.2k to 27k would do I think, and a slightly bigger one (MR25 series perhaps rather than the MR16 one I used) would probably be a bit more robust.


Temperature now reads a 8˚C, and the repeater agrees.


So blow over the paddle-wheel and, magic, knots again!


In a few weeks I'll wire the new 10k NTC I have just bought from eBay in place of the fixed resistor, and, if I can be bothered, glue it to the inside of the hull next to the speed sensor's hull fitting.

Hope the above useful to somebody.