Taranis x9d+ not powering up - processor, reg and switch OK

Hardware help and support for the FrSky Taranis
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WoodyInNY
Posts: 2
Joined: Mon Sep 02, 2019 8:33 pm
Country: -

Taranis x9d+ not powering up - processor, reg and switch OK

Post by WoodyInNY » Mon Sep 02, 2019 8:56 pm

Thanks for the great resource. I've been working through some of the other threads here attempting to narrow down the possible issue. Here's the summary so far:
  • Taranis x9d+ with Crossfire bay module (removed for troubleshooting)
  • radio will not power up
  • worked through the main board regulator checks, including checking C64 (not shorted), L3 (not open circuit)
  • checked R76 and R77 values (30kohm and 10kohm out of circuit which, though different from values posted elsewhere, appear to be the correct ratio).
  • input to reg gets switched battery power but I only see 0.5v at the reg output (at C64)
Was troubled by the fact that, when in the circuit, the resistance values of R76 and R77 are identical at 7.5kohm (the parallel value of their out of circuit individual values) with no sign of a short anywhere on the main board that would create a parallel circuit.

I disconnected the main board from everything and checked the values again and they are no longer in a parallel circuit. Re-connecting step by step the issue appears to be related to a circuit on the back circuit board introduced by the P7/P8 ribbon cable.

I found some additional guidance suggesting checking the processor/regulator by plugging into the laptop via USB without powering up the radio. Initially this yielded nothing, and i was thinking fried processor or regulator, however i accidentally disconnected the P7/P8 ribbon cable and then got the beeps.

Probing the main board in this configuration, the voltage regulator is now working.

I don't plan to power up the radio in this configuration, but would appreciate any thoughts/advice where to check next. Is the parallel circuit formation meant to be there or is this a sign of a short circuit elsewhere?


WoodyInNY
Posts: 2
Joined: Mon Sep 02, 2019 8:33 pm
Country: -

Re: Taranis x9d+ not powering up - processor, reg and switch OK

Post by WoodyInNY » Tue Sep 03, 2019 1:43 am

Fixed it.

Turned out i had a dead short on the SD Card between Vcc and Vss. It was causing all sorts of secondary shorts.

Replaced with a new card and all is good.

That's one to chalk up to experience. I've never had a SD card fail in that way before.

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