transducer failing?

Xk59D · 21 July 2011, 10:40

while out last week my depth alarm kept going off in middle of channel saying under 1m of water. i kept resetting it and would go back to normal depths but it always came back with under 1m of water with no real pattern.

question is any ideas how i can prove the transducer is the fault and not my new GPS unit?

fwiw the speed is always bang on so the unit is seeing the GPS ok via the same large plug so i'm guessing i need to look at the transducer but not sure if i can open them up or time to stump up and gamble it is knackered?

cheers

Pikey Dave · 21 July 2011, 10:52

Without knowing what kit you have it's hard to give much advice. It could be lots of things, unit software might need updating, weed, fish under the boat, mud, temp inversion. Halocline, thermocline, transducer kicked up, poor water flow over the tx face,Etc etc. I'd rule that lot out before I started taking things apart

ee lad, tha can't educate pork

BogMonster · 21 July 2011, 11:09

Putting 2+2 together you have recently fitted a new GPS but using an old transducer? - if this is the case are you sure they are compatible? I don't have any idea what differences are and what works with what (or not) but maybe a possibility?

willk · 21 July 2011, 11:11

yeah, you're gonna have to tell us what kit you have - is it a chartplotter or fishfinder, for example?

A simple test would be to first disconnect the transducer from the network (is it networked?) and see is the result the same as the original fault. That would suggest a comms issue.

I had a transducer and fishfinder pair that failed over a couple of months and it was a little like you describe - an intermittent fault that was generally resolved by restarting the unit. The first bit to fail was the fishfinder (replaced with a potter), the original transducer failed next, that simply stopped working, eg: no readings on the plotter.

If you can borrow a compatible transducer, connect it and hang it over the side to see if the problem is resolved - it saves a lot of cable pulling!

Xk59D · 21 July 2011, 14:12

sorry for lack of info guys. btw i should add it has been ok for maybe 20 hours use since i replaced the GPS.

my kit is this-

788ci HD Combo : : Humminbird :: Marine Fishfinder

and

XNT 9 20 :: Humminbird

boat is out the water now and i looked quickly at the transducer and i can't see anything obviously wrong. problem is in maybe 1-2 hours boating i may only see this for 5 mins so gonna be a bugger to nail down.

everything seems to work properly except the depth lately.

FYI rebooting will not cure it-it will eventually sort itself out after a few mins normally.

cheers

Pikey Dave · 21 July 2011, 16:32

Does it happen randomly in any body of water i.e. deep, shallow, somewhere inbetween. Or is it usually in the same area? What happens if you reduce the gain/sensitivity, does the problem go away?

Xk59D · 21 July 2011, 16:41

it first started happening when i got some air as it were :-)

i have not played with the gain settings yet as i've only just got round to remembering it happened!

depth of water seems to make no difference and area makes no difference if that helps.

as i said it has been fine for about 20 hours or so on this new unit so if i had to bet i'd think the transducer is going but lot of work to replace it digging cables out :-(

cheers

captnjack · 21 July 2011, 16:54

Is the plastic bracket intact or is it cracked and allowing the transducer to rotate up and point partially backwards underway?

wavelength · 21 July 2011, 20:04

Quote:

it first started happening when i got some air as it were

therin lies the problem one would think esp if as you say it sorts itself out afterwards. Humminbirds I have had never coped with speed and once they lost the plot as it were it took them a while to get their acts together again. Any air passing under the hull in disturbed water will destroy readings. Whereabouts exactly is the transducer?

Xk59D · 21 July 2011, 21:43

Quote:

Originally Posted by wavelength

therin lies the problem one would think esp if as you say it sorts itself out afterwards. Humminbirds I have had never coped with speed and once they lost the plot as it were it took them a while to get their acts together again. Any air passing under the hull in disturbed water will destroy readings. Whereabouts exactly is the transducer?

to clarify-it is happening since that-coincidence perhaps but it can happen at just about any speed now.

sorry for poor piccy but all i have of the back out the water the day i bought the boat. you can just see it under the outboard bracket. the bottom of it level with the bottom of the transom.

i will check the plastic etc to make sure it is not cracked or can move when underway.

cheers

captnjack · 21 July 2011, 23:31

I'm not seeing it in that pic. Is it right next to your elephant trunk?

Xk59D · 22 July 2011, 08:01

circled now.

BogMonster · 22 July 2011, 10:04

Quote:

Originally Posted by wavelength

therin lies the problem one would think esp if as you say it sorts itself out afterwards. Humminbirds I have had never coped with speed and once they lost the plot as it were it took them a while to get their acts together again. Any air passing under the hull in disturbed water will destroy readings. Whereabouts exactly is the transducer?

I had much the same problem with my Humminbird on the old rib, over about 20 knots it more than likely wouldn't work at all and it was fitted about where that one is. I bust the bracket on mine in some kelp and IIRC it was a bit (more) intermittent (than usual) and then fell off completely so I made a new metal bracket for it but seem to remember it was a bit cranky getting the angle right on the new bracket so it might have had a knock and be pointing back a bit.

In-hull transducer, that's the answer to all problems

Xk59D · 22 July 2011, 11:51

it makes sense now the bracket is perhaps weak or getting a tweak now under way. when it first occured the back end got a bit of a knock when coming off a ferry wave. not enough to jolt me/boat but certainly enough to upset the angle of this thing perhaps given where it is.

i have never had a problem before at anyspeed reading depth so i'll go have a look at it tonight and get some more pics if i don't see anything obvious.

is there a set angle range for these to work within?

thanks for help mean time peeps.

cheers

captnjack · 22 July 2011, 17:55

Quote:

Originally Posted by Xk59D

is there a set angle range for these to work within?

Depending on the depth of the water it can be quite sensitive to changes in angle. Like when you are riding bow high and the transducer points "forward". Generally it should point straight down while underway AND while at rest. This requires a bit of fiddling and splitting the difference in practice.

Ther is about ~15degs of wiggle room on the angle, because that's how big the signal cone is. If a signal is not being returned from the bottom because its "skipping" off the bottom at an angle the unit will flash nonsense or read a very very shallow or over-range depth (I have gotten both bogus signals from my Humminbird).

The plastic bracket on the transducer has two nubs on the inside. The actual sensor is supposed to break free and swing up on impact with an object. If those nubs are worn it won't stay snapped back down though.