Sorry I don't under stand what you want me to do.
RX pack to motor mount continuity reading?
where on rx pack?

This is how you should connect the unit to the Spirit. Only through the SRXL cable. As mentioned above if you give a separate power feed to the receiver besides the SRXL connection you are risking a ground loop which is what seems to have happened to you You should plug both power feeds to the Spirit unit only.

Yes, that is correct.
A ground loop is created with multiple paths to ground. In your case, multiple paths to your single battery.

That is how I have it done. Now
Tomas thinks static hit.
ground boom to tail shaft, problem ground boom to motor mount no problem.
continuity check between rx and tail?

No, that's not how you said you have it:
"How wired, power to fbl from bat. Power to AR 7700 from bat."

They told you to remove the lead from battery to receiver (and plug it to the Spirit for redundancy).

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I no what they said I did what they said.
read what I wrote that's how I have it done. NOW!
thanks for your help.

Strato

There's only a few things that it could be:
1. Antenna blocked by CF/ bad placement of receivers. That would show in a range test

2. Static hit. Test with a multimeter. If close to 0 resistance between tail shaft and motor mount you're ok

3. Wires came out of contact between the FBL and the receiver. Some sticky tape or hot glue to keep them in place would fix that

4. Ground loop due to the power supply going to both RX and FBL. Connecting the FBL to the RX by the SRXL connection only should fix that

5 faulty receiver is always a possibility

If I were you I'd test and fix all of the above. Then would remove the main and tail blades and run a tank on the ground at a reasonably high rpm and check if the issue re occurs.

Will do.
Thanks for your help

Am I wrong here? I thought it was ok (when using the regular spirit) to plug the slave bec wire into the ar7700 and have the sxrl cable going to the rud port and have the throttle/master bec cable going to aux1?

Lots of people (including myself) have done this for years thinking it was balancing load or adding fault tolerance.
As I learned recently though, it is NOT a best practice, and instead ADDS risk of failure to your setup. This has been a very sobering and expensive lesson for me.

It seems from my observations and all the data I have collected from others to date, that a ground loop like this will be tolerated without incident for most. Adding high demand servos and high demand flying style that creates high amp loads on the power system hi-lite the fault potential with a ground loop. It seems logical that static discharges could also be a contributing factor.

As somebody that has experienced total loss of control on 2 different Goblin 700's a total of 4 times now, I will not ever configure power like this again (ground loop). Way too dangerous and expensive to risk losing control. Adding power connectors to your receiver has no upside and creates new risk.
*** I still can't prove that a ground loop was a factor/cause of my 4 incidents, but everything else has been eliminated and this is what remains.

All power should be connected to the FBL unit - as close to the main load as possible (servos connected to FBL).