Black Rain on LMS527 Sonar Screen

[lollyjoe]

I installed a new LMS527cDF iGPS in the spring. I can see the bottom & fish marks on the sonar screens they are continually obscured by vertical lines that look like black rain.


I have turned on and off every electronic device on my boat and it makes no difference:
· Main motor (tachometer)
· Kicker motor (8HP on transom)
· VHF radio
· Props stopped and turning on main & kicker motors
· Boat stationary and at WOT


I have tried taking the sensitivity off auto and I can get the “rain” to lighten up but then while I can still see the bottom I do not see the fish marks. I have had other sonars & they did not do this. Can anyone offer any advice? Is there a problem with the transducer?

[bvs]

Most problems like this are installation issues. Who installed it? I'd call Lowrance and see what they say.

[hondo]

Sounds to me like electrical interference from somewhere.

Here's some things you can try ....

Go into your Overlay Data and see if you're getting 12+ volts to the unit.

Make sure your ground is good.

Try moving your power cables and transducer cable around a bit, and away from the boat's electrical wiring, to see if that does anything to clear up the display.

Good luck getting it figured out.

[lollyjoe]

I installed it myself - followed all the instructions - or so I thought! I have contacted Linda Coit at Lowrance for suggestions.

I have connected the unit directly to the cranking battery (used a power source on console before), routed the power cable away from any others, installed ferrite filter on power cable & re-routed transducer cable away from any other cables. I am heading out on Lake Erie tomorrow so we will see how this works.

Thanks for the input...

[Wall@y@]

One question I have that I haven't seen on this thread is: do you have another depthfinder turned on and in use when you see the "black rain?' These black vertical lines on the screen usually means that your transducer for that unit is picking up the "pings" from another unit close by using the same KHZ rating ie, 200 KHZ. When the two ping cones intersect underwater then the two units will "crosstalk" by usually showing the black vertical lines. This has been my experience with the "black rain." I have seen this when using two Bottomline units on the same boat and also when using two Lowrance units. In both cases the transducer KHZ output was the same for each unit.

[VernH]

Originally Posted by Wall@y@

One question I have that I haven't seen on this thread is: do you have another depthfinder turned on and in use when you see the "black rain?' These black vertical lines on the screen usually means that your transducer for that unit is picking up the "pings" from another unit close by using the same KHZ rating ie, 200 KHZ. When the two ping cones intersect underwater then the two units will "crosstalk" by usually showing the black vertical lines. This has been my experience with the "black rain." I have seen this when using two Bottomline units on the same boat and also when using two Lowrance units. In both cases the transducer KHZ output was the same for each unit.

I've had a similar experience. Can also happen when fishing close to another boat and the bottom is hard and rocky. The rocks bounce the signal is all directions. Enough crosstalk happens to cause interference.

Earlier this month it happened to me. The other boat driver was a buddy so I told him to shut his unit off and I'd let him know when there were fish down below. The "rain" continued.

Pinpoint units could, via their network, synchronize the pings of two units. When that was done, a horizontal line was displayed at a depth that was related to the depth of the bottom and the distance between the two tranducers. That can happen when two units are very close and happen to randomly synchronize for a brief time.

Vern

[lollyjoe]

I found this site that talks about interference from a trolling motor. I emailed the author and he was most helpful.

Per his advice I re-routed all the wiring away from any other wiring, connected the unit directly to the cranking battery, put in a ferite filter, and did a soft reset (turn unit off, press & hold pages & power key till map appears).

Don't know which one of those did the trick, but Voila! Problem fixed!

http://mysite.verizon.net/restmvit/tmintf.html

[VernH]

Glad you got it fixed. Interesting article.

Vern