Fading echo on M92650-S 2KW 18″ Raymarine Radar

[Yacht Spirare]

Gday,

I need to fix my radar on my small sailboat before sailing across the ditch from Tasmania to New Zealand in a few weeks.

After 20min or scanning, echo fade to zero. All diagnostic PASS, no message displayed, seams to me that the scanner still works and is transmitting but no echo back. Radar work perfectly again if scanner is turned OFF for 20min.

I am a certified electronic technician...have look at all connections and made sure of enough voltage at the dome (over 12.8Vdc while on shore power). Cable between C80 Plotter and radar dome is ok...not sure where to go from here. Magnetron has low hours count so probably ok.

Any suggestion on what may be the problem ?

Regards,

[DeBe]

Looking at the second screen theres specly back ground noise on the screen suggesting the reciver stage is working. Posible transmit fault, is there HV power to the magnetron & check magnetron current.

[Yacht Spirare]

Thank you for the suggestion.

Radar has been working fine now for abt a week. My guess is that I had a "real bug" in it somewhere most likely now "fried" in the HW circuit ! All I did after opening up the dome for inspection is ran it for a hours every other day and one day it just kept running without any problem.

On a more serious note, it may still have a bad connection (intermittent) somewhere and the problem will come back to bite me at the most inconvenient time or else my real bug hypotheses stands ?

Cheers all,

[Hesti]

Does it have a slipring to connect to the moving (turning) parts? If yes, your problem just might be in that area (corrosion or brushes blocked)

[DeBe]

Slip rings & brushes went out with CRT type radars, quite old technology.