NavList:

I’ll indulge you.

Many of the adjustments have to be moved to their extremities in order to obtain a decent radar picture and further, the screen seems to have some permanent, though small blotches on it.

First off, is there some way to remove these blotches?

The blotches, from your description, on the screen most likely are permanent now. It sounds as if the phosphorous coating is flaking or the coating in those areas are burned and no longer excitable.

In your description of “adjustments in their extremes” I take it you refer to the manual gain, range control adjustments, PRR control, sea clutter control and fine tune adjustment knobs? The problem may be located in the magnetron unit (not good at all) or just be a section of corroded wave guide (again, not good) and not your receiver. Please advise.

Second, short of buying an entirely new radar unit does anyone out there know where I can obtain a replacement receiver. Raymarine owns Apelco now and the unit I have is extinct. I sent a note to Raymarine but came up with zilch.  I am loathe to buy a new unit at this time because I don't relish the idea of tearing everything apart and having to reinstall and re-wire. Plus, I don't want to contribute further to the increasing pile of e-waste which appears to be a growing problem in the world. Ideally, I'd love to obtain a new receiver and just plunk it in.

No can help.

But I will say this:

Decent radar units may be found for the cost of a premium sextant. And a functional radar unit is much more valuable today, than a sextant is, in every day piloting, navigation and collision avoidance.

As I said, it ain't celestial but it is marine navigation so I hope the list will indulge me.

Robert