Sounds like you speedo has a weak BEC, which cannot supply the volts to your receiver, i had this with the LRP QC2 as soon as i tried the steering the light would go out on the receiver, simple to fix just get the SPM1600 Spektrum receiver voltage protector, since i fitted that i did a whole meeting with no problems.
But if you can let us know what gear you run, just in case its something else.
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Jonathan | Atomic-Carbon
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