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Old Jan 17, 2013, 10:12 AM
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RCB1's Avatar
USA, IN, Norman
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XP9303 Encoder Boards... what exactly is going wrong?

While Horizon has been excellent on fixing encoder boards on XP9303s (kudos to them!), that may not always be the case. What exactly is going wrong with them? I know the problem seems to come from leaving the radio on until utterly dead.

Is it programming on the board, a bad resistor or capacitor? Has anyone ever investigated?
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Last edited by RCB1; Jan 17, 2013 at 10:31 AM.
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Old Jan 17, 2013, 02:18 PM
Stress Be Gone
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Snohomish, WA
Joined May 2000
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I believe that allowing the battery to run totally down results in the corruption of the memory. Depending on the severity of what happens it either requires reprogramming of the board or replacement. This has been talked about in other threads from time to time.
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Old Jan 17, 2013, 11:23 PM
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USA, IN, Norman
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I've seen a lot of threads about having to send it back to horizon, and many threads about the encoder boards being the fault, but not much as to the actual root issue or any thought as a way to correct or deal with the issue other than sending it back to horizon.
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Old Jan 18, 2013, 03:04 AM
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Joined Aug 2002
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[QUOTE=RCB1;23842459] While Horizon has been excellent on fixing encoder boards on XP9303s (kudos to them!),
that may not always be the case. What exactly is going wrong with them?
I know the problem seems to come from leaving the radio on until utterly dead.
Is it programming on the board, a bad resistor or capacitor?
Has anyone ever investigated? [
/QUOTE]

Earlier JR X347, 388, and others relied upon a small lithium battery which had a life span of 3<5 years to retain memory.
Longevity of the lithium battery depended on user switching Tx on for a few minutes weekly/monthly
to keep the alternate capacitor charged. Problems with later models (inc Spektrum then made by JR):
. JR Removed the Lithium back up Battery.
"It's because the backup lithium was removed on the later generation transmitters.
The lithium kept a constant 3V to the processor and would therefore always boot up correctly.
If the main battery is low or power is interrupted when booting up, this can cause the voltage to fall below
critical level and corrupt the processor.
JR was only responding to what people wanted. " - Theaton56.

Two previous threads, with extracts below, which may further assist:

1. JR 9303, XP9303 - Corruption in Model Memories or Blank Screen
"If you ever see corruption in the model memories, you must stop immediately and send it in for a system reset.
Continue to use it and you may corrupt the CPU, this means a new board.
They should be able to salvage model memories prior to carrying out a system reset and reload them.
It is 50/50 that they will be salvageable, when I used to do that I typically found that every 7th
model memory was lost but the others could be recovered " by theaton56 (ex JR UK Service person)

2. On a good note: Did I just kill my XP9303last post:
" Followup, Just to follow up on this, I got my XP9303 back from Horizon yesterday, all repaired and shiny.
As Bayward predicted, they replaced a failed encoder board.
There was no charge, even though I am not the original owner of the tx!
So three cheers for Horizon customer support! -- Al Evans

Much more information, including DIY repairs to JR Transmitters with failed memory, available below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.
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