Old Transducer with a new Depth Display?

[hriehl1]

I removed a very old mechanical-dial style depth display from my boat that I was told did work "some of the time". I have not (yet) removed the bronze thru-hull transducer with the 2 wire leads and am wondering if this older transducer may work with only a new digital display (assuming the problems with my old unit were more likely the mechanical-dial display, not the transducer).

I see transducers come (generally) as 50kHz and 200kHz or dual frequency. Any ideas on the whether I can avoid replacing the old transducer and just get a new digital display unit? Or where there is a good web resource on this? I've spent the better part of 2 hours trying to research an answer without luck, though it does seem some depthfinders are sold as separate display and transducer units.

Thanks for any help you can provide.

[ilikerust]

I have the same situation, except my old depth sounder works just fine.

But I bought a brand new Garmin GPS chartplotter that has a depth display, which requires a new transducer. I am seriously doubting that the old transducer will work, as we're talking about probably a 30-year technology gap.

I'll be interested to know what you find out, but I doubt the old one will work with the new digital tech.

[sailingdog]

It depends. Many of the transducers are/were made by a single company—Airmar. Many of their transducers were made to work with multiple displays. I've used the transducer that came with my Raymarine instruments with a TackTick display head that replaced them.

How old is the transducer and what frequency does it use. If you can find a display head that uses the same frequency and has the same number of wires, there is a possibility that it would work with the old transducer. However, do you know the transducer works? If not, then don't bother and just replace it.

[ilikerust]

I'm wondering if the old transducer would have been made to work with a different amount of voltage or current flow than is used by the new, modern digital display?

It's been my experience that older technology tends to require more power to run than modern tech. Modern computer chip technology requires much less power than stuff made in the 1970s and `80s. My concern would be that the modern digital display would not be able to "drive" the old transducer properly or - worse - that connecting it to the old transducer would potentiall damage the new (and very expensive) unit.

I'm wildly theorizing here of course, and would love to be set straight. If I can simply hook up my brand new Garmin to my old depth transducer and eliminate the old depth sounder gauge, without having to buy a new (expensive) Garmin transducer, pull the old one and run a new wire, I'd love it.

[carl762]

The transducers are not that expensive. Get a new one. You'll want all the functionality your Garmin offers, I assume? If you get a transom mounted transducer, you'll get water temp readings.

[ilikerust]

Originally Posted by carl762

You'll want all the functionality your Garmin offers, I assume?

Yeah, that's what I was thinking.

Just another three-digit expense on the boat, and another project to install the damn thing.

Since my old depth sounder works fine, I'm not in a big hurry to do this particular project - particularly since there are so many others that are much higher priority (like rebedding just about everything on the deck to stop the leaks when it rains...).

[sailingdog]

Originally Posted by carl762

The transducers are not that expensive. Get a new one. You'll want all the functionality your Garmin offers, I assume? If you get a transom mounted transducer, you'll get water temp readings.

The thru-hull ones also give water temps in most cases.

[SJ34]

If your old transducer sends a 4-20mA signal then it may work. Just a matter of matching the connector to the terminal at the back of the display.

[Maine Sail]

If it's a 200Khz transducer it will likely work with Raymarine and some others that are 200Khz. Done this many times.

The center conductor of the coax cable is hot and the shield becomes ground. To confuse everyone the new Airmar transducers are often three wires, hot, ground and shield. When using an old coax transducer just make the center conductor hot and the shield the ground. On the ST-60 you can just ignore the shield input and use ground and hot and it will work fine if it is a 200Khz unit.

There were very few older 50Khz transducers unless for fish finders. Most of the old ones for depth only were 200 or 210 Khz. If it is a 210 it won't work well with a newer digital read out. I am using a 31 year old Radarsonics, 200Khz transducer with a 2010 Rayamarine ST-60.. I also have the Raymarine unit mounted as a shoot through for back up.

Cut the RCA or termination off the end and strip the jacket from the coax:


Use a mechanics pick to un-braid the coax shield wires:


Twist the shield nicely and turn it into it's own wire:


Wrap aluminum foil around the center conductor then place heat shrink over the wires and shrink. Then install crimp terminals to fit your display:


Plug the red/center conductor into the hot or "BLUE" if using an ST-60 and the shield or black into the ground or BLACK slot if using an ST-60.

BTW my 31 year old transducer was one of the few items to survive my lightning strike this summer even though every ST-60 device on-board was fried. The damn thing is still going....

[ilikerust]

Gawd, I love this place.