Problems with SCX-20

[mikehar]

I'm having a problem with my TZ3 display and my SCX-20. All of my firmware is current. I have setup my SCX-20 as the primary GPS for the TZ3. When I turn on my N2k network, the TZ3 finds the SCX and all is good. However, after a short period of time (less than an hour) it reverts to its fallback GPS. I have several other devices using the SCX and I can watch the PGNs in N2kAnalyzer, and it looks fine. But still the TZ3 seems to lose track of the SCX. Any suggestions on how to debug this?

 

[mikehar]

One other oddity that I've noticed is that the SCX also stops responding to the configuration program about the same time. Still is transmitting PGNs, but I have to restart it to bring up the config program. No bus errors, no device conflicts, nothing obvious.

 

[Bayhouse]

When this happens, is the SCX20 still in the sensor list on the TZT3?

 

[Quitsa]

I will be interested to see what the Furuno techs say. I have had my SCX-20 "disappear" a number of times also. One theory I have is that it may be related to a transient voltage drop. The SCX-20 on my boat has quite a long run of cable being mounted on top of the sunshade on the tower helm. It is the farthest device from the NMEA 2000 power tap and thus would see the lowest voltage. On the other hand, it has done it when the engines are running and there is 14V input so I cannot see how it could drop enough to cause a problem.

 

[mikehar]

The interesting thing is that it only drops from the TZ3. It's the primary GPS source for everything else (Timezero Pro on the PC, etc.) and they don't seem to have a problem.

 

[mikehar]

When this happens, is the SCX20 still in the sensor list on the TZT3?

I'll have to check, but I don't think so.

 

[DannyAtSowilo]

Same with me. TZ Pro is steady. TZT3 sometimes displayed "Position lost" and went to back-up.

Sollution:
Disabled the GP-33. (unplugged N2k cable). So if SCX20 smokes - I will just plug in the cable in GP-33. Semi automatic.
Same with the magnetic compass PG-700 and "Heading lost"
Ja-ja-ja / I know it is a dirty sollution but it works.

My guess:
When both SCX 20 and GP33/PG700 are sending N2k telegrams it will confuse the TZT algorithm for "best unit".
Maybe it is enough that it reads 2 telegrams from PG700 to decide it is the best ???
This algorithm is written better in TZ Pro.
If only SCX20 sends it can not be confused.

Maybe a tech can comment?

 

[Quitsa]

The interesting thing is that it only drops from the TZ3. It's the primary GPS source for everything else (Timezero Pro on the PC, etc.) and they don't seem to have a problem.

When mine drops, my 711C autopilot will alarm and give a "Heading source changed" message. I have an Airmar WX220 weather sensor that puts out a heading PGN so it switches to that when the SCX-20 drops. But if I then go in and manually select the heading source on the autopilot, the SCX-20 will be back on the list and available. So when it drops, it must be for a very short time.

 

[Peter Parker]

I notice that I always get "HEADING LOST" on my TXT3 after about 5 minutes of on time for 2 seasons now. I had read the Nema connections could be the problem. l Had removed the connectors, cleaned and replaced but same issues. I am using Ancor NEMA kit. Would like to replace this unit with another brand next season.

 

[DannyAtSowilo]

When mine drops, my 711C autopilot will alarm and give a "Heading source changed" message. I have an Airmar WX220 weather sensor that puts out a heading PGN so it switches to that when the SCX-20 drops. But if I then go in and manually select the heading source on the autopilot, the SCX-20 will be back on the list and available. So when it drops, it must be for a very short time.

I agree that the SCX-20 never drops. It is the TZT that wrongly believes it has a better choice (the backup).
Three indications:
1. The TZ Pro does NOT have the same problem. Indicating that SCX-20 never drops.
2. It will switch back to the SCX-20.
3. My dirty sollution is to remove the other choices (PG-700/GP33) and now I do not have any problems - TZT does not lose heading/position.
Also an indication that SCX20 never drops. But just that TZT wrongly jumps to the back-up.

 

[Quitsa]

I agree that the SCX-20 never drops. It is the TZT that wrongly believes it has a better choice (the backup).
Three indications:
1. The TZ Pro does NOT have the same problem. Indicating that SCX-20 never drops.
2. It will switch back to the SCX-20.
3. My dirty sollution is to remove the other choices (PG-700/GP33) and now I do not have any problems - TZT does not lose heading/position.
Also an indication that SCX20 never drops. But just that TZT wrongly jumps to the back-up.

My experience is different. The SCX-20 is definitely dropping although very briefly. I will get a brief position lost error until the TZT 3s switch over to a secondary sensor. My NMEA2000 network has a ridiculous number of GPS sensors on it -- two TZT3s, one TZT2, an Airmar WX220, and the Digital Yacht AIS transponder plus the SCX-20.

 

[Bayhouse]

My experience is different. The SCX-20 is definitely dropping although very briefly. I will get a brief position lost error until the TZT 3s switch over to a secondary sensor. My NMEA2000 network has a ridiculous number of GPS sensors on it -- two TZT3s, one TZT2, an Airmar WX220, and the Digital Yacht AIS transponder plus the SCX-20.

I have a few more sensors than you and have never seen this problem.

 

[Titanic II]

When you connected the N2KAnalyzer did you check the device instancing conflicts tool, if there are device conflicts it can effect the TZT3. Also please check the NMEA2000 output PGN's on the TZT3 and turn OFF all of the GPS position PGNs outputs 127258, 129025, 129026, 129029, 129033, 130312, 130313, 130314, 130316 all to OFF