Raymarine ST60 Depth -- a very odd problem

[Anonymous]

Suddenly, my ST60 Depth meter has started to read 'Last' after being switched on for more than a few hours. If I turn it off, it works fine again, for a few hours. Presumably it is a thermal problem (battery volts are absolutely fine and I monitor volts constantly). Is the problem likely to be in the instrument or the transducer?

 

[pelissima]

Had (and have) a very similar problem on ST60 wind.
As you also note, voltage was fine. However, I considered 13.5 or higher as fine. I mean under power or under 220V at shore. But this exactly is when my ST60 failed. It never failed under 13Volts.

 

[Boots]

I get the same display, but usually when the depth is getting a bit shallow i.e. when I'm using the approach channel in or out of Chi Marina.
"Last" is follwed by the depth reading, and then corrects itself as the depth of water increases. It happens whether I have just switched it on or, it has been on for several hours.

Didn't occur to me that it might be a thermal problem.

It seems as though the connection that I was making between the display and shallow water could be wrong!

 

[tross]

Ah! I had the same problem on mine a few weeks ago. It was £90.00 to have it fixed, but I did it for 12p but as an ex-electronic engineer I had an advantage. The symptoms i had was same as you, after a while it would stop reading and flash the last depth sounding. I was faced with the same problem you will have - do I get it fixed or do I buy a new one? Well, as my car has just given up ( completely dead ) , the washing machine stopped working, and now the echo sounder! I had no choice ( or money) I had to have a go at fixing it. I chased the circuit out from the tracks and the components - it's not that a complicated circuit.

Have you had any moisture in this device over the winter? If so,
I would suspect it is the 200KHz oscillator - this is a Colpitts oscillator ( inductor -capacitor) - do you know any engineer that has an oscilloscope you can borrow. you should see a 200KHz burst on the wires to the transducer. My problem was the moisture cause tracking growth under a couple of capacitors and resistors. The design they used involved very high resistor values - 1Mohm and 3.1Mohms for a voltage divider - it didn't take much to upset that balance.

 

[Anonymous]

Thanks, I'm also an electronics engineer and I do have a scope. Maybe I'll just wash the board in IPA and dry? What do you think?

 

[tross]

Give it a try, if id doesn't work, PM me and I'll see what I can do to help you.

 

[Anonymous]

Many thanks /forums/images/graemlins/smile.gif

 

[grandcoeur9999]

My ST60 Depth meter also read 'Last' after 30 minutes. if I turn it OFF and ON I get a reading but after 2-3 minutes I get the same message LAST and if keep flashing sometime for more then 5-10 minutes.

I am not an engineer !!!! Would you be able to give me some advise?