SL70/RD218 not showing targets

[cowbayalbin]

Hi everyone -

new to the forum, thought I'd post this question here after finding a lot of useful advice in the archives:

My new old boat came with an old Raytheon SL70 unit and a RD218 radome. It powers up, the scanner rotates but shows no targets/shoreline/whatever. If I turn gain way up to 93%, it displays some speckles and an obvious rotation pattern, black screen with rotation pattern above that.

From other posts in this forum I've learned to run the debug and self test programs - the debug screen shows S 50 G 207 in the first line, then C140 F55 S0 in the second line

The self test window shows 447 hours on the heater, reset count 0, and a pass on everything EXCEPT 2 values:
These are Receiver supply 5v FAIL and Receiver supply 12v FAIL.
Modulator Current SP, MP, LP readings are 113, 120, 131 respectively
Rotation time 2458, STC preset max 149

As I'm unfamiliar with these units, can anybody help suggest where to start troubleshooting regarding the two FAIL readings? I'm a bit confused as to why there seems to be power to both units, cable passes self test, magnetron heater, tuning, heading etc. pass self test, but the power readings indicate some issue. I'm grateful for your suggestions!

Paul

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Paul,

Based upon the symptoms reported, the internal circuity of the RD218 Radome has failed. Unfortunately, Raymarine has not produced these radomes in several years and can no longer service them. Accordingly, restoration of radar features onboard the vessel would necessitate that the radome be replaced with a compatible second hand radome or that the SL70, RD128, and radar cable be replaced with currently manufactured equipment.

[cowbayalbin]

Thanks Chuck for getting back to me so quickly on that issue! Before I shell out the cash (more here in Canada) for a new system (don't think I'd want to spend money on replacing major parts of an obsolete system with questionable used bits) I'll take the unit apart and see if there's anything fairly obvious that appears fixable. Any idea which circuitry specifically might be suspect given the symptoms I described?

[Chuck - Raymarine - Moderator]

Paul,

Unfortunately, providing procedures for repairing Raymarine products is beyond the scope of support which we offer. That said, the described symptoms are typically associated with a failure within the circuitry of low noise converter (LNC). This symptom would not be associated with any loose parts/cables within the radome.

[cowbayalbin]

Many thanks Chuck - glad to find knowledgeable help here even with technical details of obsolete analog systems! With that information it might be easier now to convince my wife to let me buy a new radar before the dark and foggy season...
Cheers,
Paul

[Chuck - Raymarine - Moderator]

You're welcome.

[DreamQuest]

I also have an SL70 radar that is not showing targets. But with some different results after running the built in test. The Cable Test Status is always a Fail. All other tests = Pass, with what appear to be good numbers in all of the fields.
I have also done a resistance check per the attachment in one of the other threads in this forum. There are no opens in the cable. I have checked all 4 signals, Video, Azimuth, Data I/O and Trigger from end to end reading from the round connector on the display through the scanner as indicated in the attachment.
I also removed the Molex connector on the scanner shorted pins 1&2, 3&4, 5&6, and 7&8 and read 3 or 4 ohms from the appropriate pins on the round connector. I have a 25 meter cable.
I then read the same above Molex connector pins for the 4 signals on the scanner Molex connector back through the display circuitry with the round connector attached to the display and saw 150 ohms for all 4 signal lines. So I'm very confident that I don't have an open cable.
I find the posts in this forum to be very informative and useful. However, I am now stumped and could use your help.

Thanks,

Ken

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Ken,

This problem may be rooted within the radar circuitry or within the cable itself. Unfortunately, Raymarine's Repair Center can no longer bench check / service analog radar transducers. Please note that the analog radar cable test is not always conclusive. The only way to to absolutely determine whether the problem is rooted within radar cable or the radar transducer's circuitry would be to test the radar transducer with another cable.

[DreamQuest]

Chuck,

Thank you. I really appreciate the quick response.

Just wondering if there is a document that describes the 4 signals in more detail; Azimuth, Trigger, Video and Data I/O? My display is not showing targets, so I would assume no video.
But I also don't see a circular sweep. Is that also in the video, or Data I/O, or does it have to do with the trigger. Or is the trigger just the signal used to turn transmit on and off. Just guessing.

Thanks,

Ken

[Chuck - Raymarine - Moderator]

Ken,

Please click here to view a FAQ addressing your latest question. However, the symptoms reported are associated with a problem in with video transmission ... again either rooted in the cable or within the radome's circuitry.