Fish Finder Debug

My fish finder crapped out and hopefully someone here can give me an idea of how to debug it.

When I plugged it in after the long trek to eastern Oregon, it would power up but nearly the entire screen was black (all pixels turned on).  No depth was showing and the menu button didn't work.  It's the same screen I get when powering on without the transducer installed so I tried cleaning connections but that didn't help. 
The transducer did take a little hit on a rock but I'm not positive that's the problem. 

Anybody have any ideas on debugging this?  Where does one get a new transducer if that's what it turns out to be?

I have no idea Spot on debugging the little buggers.  Does your model have a simulation mode?  You can often use this to determine if it's the transducer or the main unit.  If the simulation works and the screen is fine, then it's probably your transducer.  If the simulation doesn't work, it's probably the main unit.  As for replacing the transducer, well, you can just about buy a new fish finder (closeout Cuda 168 ~ $60) for the price it cost to buy a new transducer.  Your fish finder is a bit old so finding a new transducer might be tricky.   I usually look at old failed equipment like this as a sign to upgrade.

Brian

 I usually look at old failed equipment like this as a sign to upgrade.

Brian

I really hate the thought of wasting the $20 I spent on this unit!  Besides, the geek in me would be emasculated if I didn't at least try to fix it. 

I'm sure if anyone can figure out how to fix that unit it will be you Spot.  After all, you're the one that successfully shortened his transducer cable with out any ill effect.

Maybe take a can of electronics cleaner and spray the connections, then scrub them a bit with an old toothbrush (or even better, a soft wire brush).  It maybe that your recent saltwater excursions contributed to its demise (a little dielectric grease on the plugs can help with this). 

When I tried to buy an extra transducer cable for my Eagle 242 (basic GPS model), I found that I could buy a new Cuda 168 (uses same cable) for less than the cost of ordering a cable by itself.  They wanted something like $60-70 plus shipping.  Fisherman's had new 168's for $65 bucks.

I'm sure if anyone can figure out how to fix that unit it will be you Spot.  After all, you're the one that successfully shortened his transducer cable with out any ill effect.

Doh!  Are you suggesting that my current woes are somehow related to the shortening of my ducer cable?!?!?  Them's fightin words boy.

Just for that I'm going to fill in my secret ling trench with sand.   

Spot, no, no.. I'm not suggesting that your problem is related to your cable. Rather, you seemed to have good luck fixing yourr electronics.

Brian

FOLLOW-UP:

I was really looking forward to owning a new fish finder.  Not really looking forward to spending money on one though.  Also, I'm not one to give up without at least finding out why.  So, I found some time and sat down with my gear and a multimeter. 

I probed everything and couldn't find any opens or grossly high resistance.  There was a little variability in the areas where I'd caked on the dielectric grease but nothing appreciable. 
I cleaned all the connections and plugged everything back in and voila!  Like magic, it worked perfectly........  This was good news but not all that satisfying.

When I installed the wiring for my FF, I'd cut down the power and transducer cables to keep it clean and reduce the potential for snagging gear that was stowed below deck.  I later found out that this is a big "no no" due to the impedance matched cable length on the transducer.  (I really should have known this before ever cutting it).  In talking with some EE's that I work with I was told that I probably just got lucky and managed to cut exactly the right length and obtained exactly the right resistance at my connections.  Bets were offered on whether I could repeat this feat and the conversation was mentally stashed away under the titles "Doh", "Luck" and "Fishfinder".

Fast forward to Sunday:
In anticipation of time on the salt I liberally reapplied dielectric grease to all my connections.  When I plugged everything in on the water, guess what..... Zero depth and a black screen.......  It was seeing the transducer but not getting the correct signal.  That's when it dawned on me, "too much dielectric grease".
 
I pulled the transducer connection (a 2 pin trailer connection), cleaned out the dielectric grease (and a bit of sand) from both ends of the connector, plugged it back in and voila!   I was back in business and had a satisfying answer to the original question!

Nice one spot and thanks for posting. I never knew that too much dielectric grease could make things go bad. I will keep that in mind when it's time to re-coat all the connections again.

Z

Doh!         i totally forgot that when this 1st came up too... have had it happen sevral times on the Milspec gear i work on ...just must've been too tired to make the mental connection..

good perserverence in troubleshooting Spot, most guys would've written the gear off at the point you pulled things apart