older norcross depth sounder dim reading

[grumol]

this depth sounder is a hawkeye with cable, not wireless or handheld, mounted in hull -- have used the unit for 2 seasons -- has always had the problem of a "random" display -- upon closer examination, the display is always there, but you can''t see it, i.e., i can see the numbers if i put my face up close to the unit, just the outline of the numbers, and they are getting accurate readings -- the black part of the numbers, however, comes and goes -- any ideas?? -- thanks, bob