Topic: Old 597 DI - Head or Transducer Problem?

[skipt]

Love my 597 but noticed recently that sonar isn't working.  I only get a very small trace near the surface, even after resetting to factory defaults.

DI works most of the time, although it doesn't seem as sensitive as it used to be, and every so often fails to work at all.  Power cycle or factory reset usually fixes that.

I am willing to go for a new transducer or head, but would like to make the best possible guess as to which one is more likely the problem.

I am an engineer so apologies if the following is too _nal.

I remember when the unit was much newer years ago, you could really tell things were working when the transducer was powered and out of the water.  I could hear clicks and pick them up on a nearby AM radio.  Putting a fingertip on the transducer actually caused a little pain.  None of this happens anymore, so I suspect either the transducer and/or the driver electronics in the head have degraded.

I disconnected the transducer from the head and upon power up the head correctly reported that the transducer was not connected, so there is some connectivity there.  The temp sensor is working fine too, I can raise the temp with my fingertip.

I'm thinking of either tapping into the transducer cabling and putting a scope on the leads to see the driver pulses and signal responses, or, opening the head to inspect the driver circuitry.  I would expect inside the head to find a large capacitor and maybe one or two power mosfets in the driver circuitry, and if so, might remove those components and check for degradation/failures.  I'm also wondering if the head has an internal coin battery for NV memory retention.  Those batteries don't last forever.  Does anyone know in advance what I will find?

Another alternative would be to put the head on the bench and use some resistors to simulate the transducer elements.  I have the pinout for the transducer cable and would use a scope to look at the driver pulses.  Does anyone know a good resistance to use and what size driver pulses I should expect?

NOS transducers are available but I'm wondering if they can degrade during years of sitting on the shelf.  I imagine internally the transducer has the elements encased in epoxy which would seem to be a pretty stable environment.  Opinions or facts on this welcome.

[rnvinc]

Do you have access to another compatible transducer for troubleshooting  ... ??

Rickie

[skipt]

No I don't.  I might buy one but first trying to get smarter, like I said, it might be the head.

[ezfishn]

Rickie is far smarter than I on these units but I believe the DI is dependent on the 2D working.  So if your DI is working then the 2D should also.  Also, true the transducers can age over time and become weaker.  Where is your DI transducer mounted?  Are you getting a valid depth reading?  I'm fairly certan there aren't any internal batteries in the units. 

[skipt]

The engineer in me is suspicious that the DI depends completely on the sonar working properly.  Here's why:  the active element in the transducer is most likely a piezo ceramic like barium titanite, and such an element will have a resonant frequency that depends on the geometry (physical shape and dimensions) of the element.  The fact that DI and sonar use different frequencies suggest that there is a separate element for each function, each with its own physical size and resonant frequency.  Also I'll note that my transducer (710226-1 XNT 9 DI T) has separate signal wires for the DI signal and the sonar signal.  This further indicates that there are separate transducer elements for DI and sonar.  And if there are in fact two different elements in the transducer, it would be possible for one element to degrade at a different rate than the other. 

Regarding depth determination:  if there are in fact separate transducer elements for DI and sonar, both the DI and the sonar would be capable of determining depth.  Depth is determinized by the arrival time of the return pulse and the (known/fairly constant) speed of sound at the given frequency in (fresh or salt) water.  The imaging however (DI or sonar)  is determined by the strength (not the arrival time) of the return pulse, which depends on the density of the reflecting structure AND the receive sensitivity of the transducer element(s) and the sensitivity of the receive electronics in the head.  I've already stated there may be separate elements for DI and sonar, and there also may be separate receive electronics in the head for each function.  So there are lots of different ways for the 597 to be designed and lots of different ways for the performance to be degraded.  Unless someone with some inside knowledge steps up, I'll be turning over rocks for a while longer.

If anyone has any dead transducers laying around I'd be happy to cut them open (I do stuff like this all the time) and we could all learn more about transducer internals and their possible failure modes.

My transducer is mounted on a trolling motor, I usually only use the 597 when trolling.  I am getting valid depth readings and decent images using DI, although the DI images don't seem as crisp as I recall when the 597 was new.  Next time out I'll check to see if I am getting valid depth readings when using sonar only. I still haven't opened up the head yet, but that day may be coming.  When I do that I might be able to determine if there is separate circuitry for DI versus sonar, and if there is an internal battery to retain user setting across power cycles.

UPDATE:  WOW, I found this video showing showing a 597 transducer leaking some goo:  (about 50 seconds into the video):

https://www.youtube.com/watch?v=cOctMvqZaN0&ab_channel=DinsmoreOutdoors

I know that the transducer elements need to be acoustically coupled to the transducer housing but I thought they were doing it with epoxy, so this goo is a surprise.  And then, upon close inspection of my transducer, the pointy end seems to have a hole that seems to be sealed with some black silicone-like RTV stuff.  I bet they inject the goo and then seal up the hole.  More stuff to ponder I guess.

[rnvinc]

I think ezfishn was referring to the idea that we know SI imaging uses depth from the 2d piezo in the processing and displaying the SI image  ... I have no documentation if this is also true of the DI core unit models  ...

Some of the larger DI core units (858 DI and larger) had a setting to allow digital depth from either the DI piezo or the 2d piezo  ... I cannot find that same setting in the manuals of the smaller DI core unit models  ... So is either piezo capable of depth - yes. Your 597 DI model - I do not know ...(manuals are here https://www.humminbird.com/support/manuals?_ga=2.228808924.1597017917.1662521143-1384636803.1662426675)

I have been in the SI xducers to verify that the 2d piezo is round and imaging piezo(s) are bar shaped  ...






I also know that Humminbird uses many different materials in their transducer construction  ... and probably more materials than I’ve seen in the transducers I’ve cut into  ... there was no “goo” in this SI transducer  ...


Here is good info about transducer theory and piezoes  ...:
https://www.airmar.com/uploads/installguide/Theory-of-Operations-2014.pdf

Rickie

[skipt]

Great info Rickie, that helps a lot.  But in your cutaways I don’t see any goo.  I expected the internals to look more like your photos, that’s why the goo was such a surprise to me.  I need to think more about where that goo might have come from.

I suspect the 597 transducer has a disk-shaped sonar element at the wide end of the transducer teardrop, and a bar-shaped element along the remaining length of the teardrop for DI.  This arrangement would be consistent with the beam patterns described in the user manual: a disk shaped element would have a cone shaped beam pattern and a bar shaped element would have a thin rectangular beam pattern perpendicular to the long axis of the bar element.

I have the 597 manual and know the menus well, and you are correct—there are not separate settings to choose which element (DI or sonar) provides the depth reading.  But I believe there are two separate elements and the head uses each one independently for depth readings.

This morning I now have no depth reading on DI or sonar, whereas a few days ago I had depth on the DI but (as best I recall) not the sonar.  No more images on DI either.  So the failure is spreading but I still haven’t decided if it is the head or the transducer.

My next steps (short of buying another head and/or transducer)  could include any of the following in any particular order:

1)   Open the head and inspect for signs of electronics problems such as leaky caps or burned components
2)   Put the head on the workbench and using resistors try to fool it into thinking the transducer is connected.  Then look at the head’s transducer outputs for the transmit and receive signals with an oscilloscope
3)   Leave everything on the boat and tap into the transducer cable (there is plenty of spare length readily accessible) .  Measure each element’s impedance characteristics as described in the attached figure.  Then connect the transducer to the head, power up and using the taps, look at the transducer’s transmit and receive signals with an oscilloscope

UPDATE:  On a whim I connected a multimeter (set to AC volts) to each transducer element via the transducer cable pins, and tapped on the transducer.  Both elements generated an AC voltage (sometimes 2-300 mv) on the multimeter.  This suggests the transducer isn't completely dead/open circuit.  Probably the next step is to open and inspect the head.

[rnvinc]

In my mind the “goo” would most likely be a happenstance of an epoxy scenario not setting up completely/correctly  ... uh.. maybe a reason Humminbird was so adamant of fixing the guy’s issue in the video post you linked ..

I can’t imagine a long term acoustic advantage of liquid inside a transducer housing ..

I also can’t imagine that these HB transducers (operating at their known power level) could cause enough heat to melt anything  (like Airmar deep water transducers could)...

Rickie

[rnvinc]

BTW ..  I will check my transducer collection and see if I have a XNT 9 DI T that we can use for your troubleshooting  ...

Rickie

[rnvinc]

Also BTW  ... Please note that no Humminbird representatives actively follow this forum  ... (although a HB rep does occasionally pop in)  ...

We, at sideimagingsoft, are merely users sharing info with users  ...

Rickie

[skipt]

UPDATE:  So I opened up the head and found no obvious burned components or leaky caps.  I spent some time looking at the layout and took some photos, but later found that a picture of the transducer input cable pins I found online wasn’t quite correct, and that hampered my attempts at any detailed circuit tracing.
 
It looks like the transducer driver circuit has 3 power mosfets stacked up and (as discussed below) I believe each transducer element is driven at a different voltage level by tapping off of this stack in two different places.  Power for the driver circuit comes from a very small step up supply of some sort (voltages described later) but the main IC and all of the supporting components were low rated, very tiny and difficult to identify.  This is consistent with the notion that the transducer drive needs high voltage but very low current.

It looks like only a single receive circuit suggesting that the DI/sonar returns follow a common path until some filters are used to separate the DI and sonar signals based on frequency.  All of the filtering seems to be analog.  I also in-circuit checked the mosfets and as many diodes as I could, found no failures.

Having found no obvious problems inside the head on my workbench, I tapped into the transducer cable on the boat. For starters I found a picture online of the transducer cable connector wiring, the picture was clearly labeled with my exact transducer number, but the picture didn’t align with my dissection of the transducer cable.  What I found was that each transducer  element has its own foil-shielded pair.  Anyone who needs details for my exact pinout feel free to contact me.

Once I figured out which wires did what, I found some interesting things.  I found that the head uses the transducer thermistor resistance to decide if the transducer is connected or not, even if the elements are still connected.  I found that when I tapped the transducer the DI element was generating voltage, but the sonar element was not.  I then hooked up an oscope, installed the head and powered up.  I could see the drive pulses to each element but no reasonable return signals because I didn’t have the transducer in water.  The sonar element was driven by a pulse of about 28 V peak and the DI element was driven at a much lower voltage, about a third of the sonar pulse. Both driving pulses come out of the head at the same time but they are sent to each element via separate wiring.

Since the head seems to be driving the elements and the sonar element generates no voltage when tapped on the outside,   I believe the transducer has failed, in particular the sonar element.  It appears that they drive the sonar element harder and use the sonar for depth measurements, and maybe the harder drive causes the sonar element to give out before the DI element.  Anyway I ordered a replacement transducer and once it gets here I’ll update hopefully reporting that the problem is gone.

[skipt]

I received a new transducer, appears to be the correct part, but only has 4 pins instead of 5.  Should I be concerned?

[rnvinc]

In the XNT 9 DI T only pins 1, 5, 6, and 7 are used  ...

Other random pins in this specific transducer can be attributed to the fact that HB makes their own transducers and they could have grabbed any number 9 connector (regardless of quantity of pins) and only used the circuits necessary for the specific xducer  ...



Rickie

[skipt]

Yes, I found that image on line, and used it when I tapped into my original transducer cable.  I found differences between that image and the wiring of my transducer.  I have a new transducer on hand and am preparing a detailed comparison of the wiring, as best I can determine without tapping into the cable of the new transducer.  In the meantime, attached are two images showing the labeling and pinout differences between my original and new transducers.  As you can see, one has five pins and the other four.  Also attached are two pictures of the transducer connector inside of the head, you can see that all five pins are wired.  I WILL get to the bottom of this.

[skipt]

Here is a table showing what I found when comparing the connector figure against the wire colors when I spliced open my original (490391-2) transducer cable.  The orange and black wires in the cable were swapped (opposite pins) relative to the picture from the internet.  What is odd about this is that even though the orange wire inside the cable was on a pin different than shown in the figure, the orange wire was still paired with the purple wire and wrapped with shielding as shown in the figure.

I did find this, but nothing that explains the wiring differences:

http://www.bbcboards.net/showthread.php?t=972879

http://www.bbcboards.net/showthread.php?t=972879

[rnvinc]

In the core DI units there are only 4 circuits used or needed  ...

Pin #1 is DI positive
Pin #5 is Temp positive
Pin #6 is 2d positive
Pin #7 is common drain/ground

Pin #3 is only functional in the SI transducers for the left SI positive  ...

Rickie