"Bruce in Alaska" wrote in message
...
In article ,
"Sun Dragon" wrote:

I have a small Furuno radar where the echo return image is missing on
the
left and right portion of the screen. The fore and aft images are fine.

I suspect the "brushes" or slip rings in the scanner unit are worn in
the 2
o clock thru 4 o clock and the 8 o clock thru 10 o clock regions.
Am i correct in this assumption and if so, are kits available to renew
the
contacts in the scanner?

Thanks,

Capt J. Vincent Collins
Master Oceans
F/V Sun Dragon



Depends on what model of Furuno display you have.... Most newer displays
have computer generated sweeps, and are Raster Displays. Should you
actually have a PPI with a real rotating Deflection Coil, do the
Range Rings, ALSO disappear along with the Targets? If Yes, then could
be the SlipRings, and or Brushes. If No, then it isn't the SlipRings
and or Brushes, as the Range Rings also have to go thru the same
connections as the target video. When you turn the "Gain" all the way
up, does the "Noise" also blank out in the same places as the Targets?
if Yes, then you have a Video problem. If No, then you have a receiver,
and or antenna problem. all the above is just basic Radar Repair
stuff....

Bruce in alaska an Old School Marine Radar Tech........
--
From Lynn, an even older marine radar tech (title under dispute)
I think the original poster suspected slip rings (and or brushes)
in the scanner unit. Unless there were some Furuno radars older than dirt
that had slip rings, none that I know of had slip rings up there. Furuno
seemed dedicated to fixed or stationary transceivers, shooting RF to and
from the antenna through a rotating or rotary wave guide coupler.
You are correct in that if the problem is in a display unit with
the "conventional"(?) rotating deflection coils, slip rings could easily be
the problem, as you pointed out.
The more recent (20 years?) Furuno's with raster scan displays
could have a video problem which would blank out 90 degree sections of the
video scan presentation at a time. The only one I ever saw with the port and
starboard quadrant targets (rings, snow and all) missing had a video
processor problem that could not be corrected (by me, anyway) without
replacing the board containing the video processor.
Heating and cooling around on that board, in the shop, running on a
simulator, would make the problem come and go. Seemed to be most sensitive
around a big ol' many legged surface mount chip not stocked at Furuno USA.
Board exchange fixed it quick enough, but not all that cheeeep.
Old Chief Lynn, 20 WPM Extra (and other wallpaper)