Join Date: Apr 2010
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Spedometer gone wild
I have an old and obsolete ST-50 Tidata instrument on my Tartan 30. The instrument has been working well for years till recently. It does the strangest things. Typicaly it shows zero speed to start, after a while it shows speed increasing rapidly to almost 100 knots and subsequently going down to zero and repeating the cycle a few times and finally settling down to a steady indication, not necessarily true one. It needs to be recalibrated every time and it holds the calibration till the next epileptic event like this. Years ago I experienced a similar thing with another ST-50 on a different boat and it never occured again.
I am reluctant to replace it with the current model (ST-60) since it is not just a plug in operation as Raytheon wants you to believe. Not just that the hole is bigger, but conections are confusing, and one runs into incompatability with other instruments. I would much rather stay with what I have, the design of the unit is great and when it functions properly it is exactly what I want. I am not able to find anyone who would work on these things.
I think that possibly moisture may be behind it. I will heat the unit keeping a 40 watt bulb next to it for several days and hope it will dry out. I will do it as soon as we launch the boat this spring.
Does anyone have any sugestions? Has anyone experienced anything like this? Is there anyone who would repair an old ST-50 instrument? Any comment would be welcome...