Another Stowe question - depth sounder

[SteveB_Sigma33]

My Stowe depth sounder keeps alternating between screen flashing, giving ludicrous readings to working fine. I've just been scrubbed by boat scrubber (bloody good job) and I think it has got better, but do you think it has

(a) Started to give up the ghost
(b) Got a huge barnicle setting up residence
(c) Something else?

Anyone had anything similar happen.

Thanks in advance

 

[jamesjermain]

If your sounder was working fine and you were getting thowse readings it would be telling you that it was getting interemittent echoes (ludicrous readings) or that it could find no bottom (flashing). You also get this sort of behaviour when the boat is out of the water or sitting on the bottom, or in deep weed or in an area of considerable turbulence (such as the prop wash of a large or fast ship.

If none of these situations applies, then it is almost certain either the transmitter or the receiver in your set is failing. One other thing is worth checking though. Is the cable from display head to transducer sound and the terminals properly secured?

 

[SteveB_Sigma33]

Good thinking on the terminals, I'll check them.

Many Thanks

 

[PeteMcK]

If it's a Dataline system, check the cable connections on the Databox and on ALL the instrument heads. A dodgy connection - not just on the signal lines - seems to be able to produce spurious readings elsewhere in the network.

I had a similar experience last year - first of all flashing fixed depth (ie, suggesting no echo) a lot more than usual, but ok in shallow water. Then the speed/log readings became intermittent too, and finally the whole system would collapse if you switched the instrument lights on. All due, in fact, to an almost-but-not-quite broken wire on the input to the wind instrument readout.

The later Robertson Dataline manuals direct you towards checking this early in the fault finding check-lists; the Stowe manuals don't!

 

[SteveB_Sigma33]

Maybe a dumb question but do you know of anywhere that has a circuit diagram for a typical setup and expected voltages?

Thanks for the info.

 

[Mirelle]

From memory, these people may have one.

 

[PeteMcK]

I'll have a look - the manuals don't give voltages (they give the supply specification only) as far as I can remember. The instrument heads are daisy-chained all the way back to the Databox. A single cable with 5 cores connects them all. One pair is +12v and ground; another pair is NMEA signal+ and signal ground - all the NMEA data runs through this continuously form the Databox. The fifth is, I think, a data return from the instrument head to the Databox, ie., user inputs, probably using the same ground as the NMEA output line.

I'd imagine there's a spec on NMEA signal voltages somewhere on the internet.