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Old Nov 21, 2010, 08:41 AM
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dstrout's Avatar
Alexandria, VA, USA
Joined Feb 2003
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JR XP-783: Carrier but no servo movement?

I dug my RC gear out of storage after 4+ years, including my trusty JR XP-783. Of course the battery was dead (8-cell MiMH). I put it on the charger overnight, powered it on the next morning, and got the "backup battery dead" beep. I turned it off & back on, and it came up fine, though with all model memories reset of course.

What happens now is that it seems to be sending a carrier but no data. If I turn it on and set up a receiver with a servo on it, nothing happens when I move the sticks. If I turn it off, the servos chatter like they will when there is no signal, and they will stop chattering when i turn it on, but then won't move.

Likewise, the ESC won't arm as it should, either. I've tried with several rx's and servos (all of whom used to work with this tx), reseated the crystal and the module. The battery reads 11.1 V 11.8 on the screen.

I can send it back to Horizon if I need to, but I'd rather not if I don't have to. any advice appreciated.

thanks,
Dave.
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Old Nov 21, 2010, 08:45 AM
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dmcquinn's Avatar
Chesterfield (St.Louis) MO
Joined Jan 2004
320 Posts
Does ther 783 have a setting for pcM VS PPM? If so, check that it matches your receivers (probably ppm)
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Old Nov 21, 2010, 09:48 AM
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dstrout's Avatar
Alexandria, VA, USA
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Bingo - thanks!
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Old Nov 21, 2010, 10:46 AM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,505 Posts
Sounds as though you'll need to have a new lithium cell installed or the transmitter will lose its memory in 24 hours or so.

It's a great transmitter and worth sending to Horizon for a proper checkup. While mine was in last time, I had them upgrade the firmware to JR 388 standard. This provides CCPM helicopter mixing, activates the 8th channel, gives you stick mode selection and a couple of other things I can't remember. Mine works as well as new and serves as an excellent backup transmitter. I have a Spektrum 2.4 module for it (for BNF models), as well as an FrSky telemetry module and a Fly Dream module. The latter is the one I use most and has worked extremely well.

The only drawback of the transmitter is that it has analog trims, so you have to remember to go through the process of setting trims back to zero if you are to avoid surprises when changing models. But at least the Trim Offset feature makes this easy.
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