Threaded Mode | Linear Mode

RKonGB

Hi, thanks in advance for any help in tracking down a pretty strange issue we're having...

I have a 35 foot sailboat that is new to me as of two years ago. Last year the old analog depth transducer which had fed an old Tridata ST50 display and an ST70, failed.

A new DT800 was installed beside the deprecated analog transducer and the DT800 was networked ONLY to the ST70 via an STng backbone. The Tridata is now entirely out of instrument topology.

The first ST800 immediately gave erroneous readings and was replaced by our Marina promptly.

The new ST800 works most of the time. However it will occasionally, and almost always while under way by either sail or power, stop reading the actual depth and display readings such at 2.3, 2.5, 2.7 feet. It will do this for a long time, many minutes to an hour or more. Power cycling the ST70, unplugging and reconnecting the DT800 and terminators or varying boat speed does not have any effect. Occasionally - the readings will return to normal. As this happens, the depth display will flash several times - and then the correct readings will appear. Once in a while - this flashing behaviour will occur, but the correct depth will never appear and the display will return to "2.7" and stay steady. The 2.7 reading will stay even if the ST800 is unplugged - so I wonder if this is a failure mode reading? Or latent signal of some kind?

I have checked for any external problems with the xducer (dove the boat with Scuba) and all appears fine.

The one action that DOES appear to solve the issue (it's worked four times in a row) is to slow the boat when motoring - REVERSE - and then engage forward. Viola! The depth readings return to normal!

We sail in the perilous waters of Georgian Bay and need to have reliable, trustworthy depth readings all the time.

I've worked through your excellent xducer troubleshooting posts and nothing has worked so far.

Anything more to check? I did see a mention of transient, ultra-short voltage drops possibly forcing the DT800 to reboot - but that doesn't seem to explain this behavior?

Further - when the depth readings are wrong - we DO seem to still see temp readings on the ST70 - so unless those are being held in some sort of cache somewhere - the DT800 seems to be "on" all the time.

Thanks for any insight!

RK