Painting DST800 depth sounder

[steve77]

We just launched and my depth sounder is not working. This is a DST800, which is a combination depth, speed, temperature sensor.

I am reading Sea Water Temperature, but no depth. I removed the transducer while in the water, and the boatyard crew had painted the depth sounder side of the transducer while they were painting the bottom. I carefully sanded the bottom paint away and replaced the transducer in its housing. No joy, still no depth display.

Question - I always thought that painting the depth sensor was not recommended because it will lead to inaccurate depth readings. Can it actually damage the transducer?

Thanks for any input.

Steve

[OldGreyB]

The typical Airmar spec sheet for the DST800 transducer housing states it is PVC with a urethane used where the acoustic window ( bottom) is. Urethane preforms very well against most chemicals and solvents.

We don't know what solvents the painters may have use to prep the boat hull, but IMHO unless you can see visible degradation to the urethane window ( bottom) casing , then the painting prep is not a likely culprit. If you can see speed by rotating the wheel and temp change from placing it in cup of cold water, then it is most likely just the depth transducer electronics has internally failed. All these electronic units are embedded together.

Test: With the unit out of the water and turned on, if the depth transducer is working, you will be able to hear an audible "ping".

If you have a "ping" and a modern MFD, then you can also look at the NMEA sentences and see if the depth is being transmitted on the network - if so has something else changed during the haul out? You may need to reselect the "data source" for the depth on your instrument system.

You don't state how old the unit is, but if you have no "ping", then unfortunately the depth transducer ( piezocermaic element) does have a finite working lifespan (50HZ = 50,000 cycles a second) and these do fail.

[Tin Tin]

We had one of these, it had special transducer paint on it which is not that effective. In any event the unit lasted 6 years then suddenly started behaving erratically and then finally died, we had to make do with a hand held sounder until we could get a replacement.


On another occasion a year later with the new sounder it failed to operate as well. I found it to be the plug on the end of the cable had gotten some moisture in it and the tiny terminal had a green tinge to it, I cleaned and sprayed WD40, dried it - worked fine after that, kept plug wrapped in clingwrap after that.





The manual says not use Ketone based type antifoul paint as this can damage the sounder face. It also says not to power wash it. Often boat haulers ask the owner to put the blanking plug in prior to haul out to avoid damaged from lifting system and pressure washing. I also thought I read somewhere that the sounder should not be operated out of the water, maybe for a minute is OK.