In this topic, consider the 2 most common reasons.

1 Turned off the software. Information is not updated, the depth is not true. After reboot may not boot, etc. In general, any problems with the software in this echo sounder are solved by the reset. It is made very simply. Open the main unit, turn off the toggle switch:

Then press and hold the left and right keys and turn on the sounder with the same toggle switch. Continue to hold the buttons until a long long peep. If the device is not booted - we take any keyboard with a PS / 2 connector, connect it to the echo sounder (processor board), go into the BIOS and just press save and exit. 

2 The cause is overheating. Unfortunately, these echosounders have a very sore spot - it's a cooling cooler (see image 1).
First, it must be cleaned and lubricated with oil. Also very often such echo sounders are mounted in the console, in which there are power supplies, etc. devices that produce heat. on some ships we made additional technological holes on the right side of the device and put additional coolers there