Taranis X9D+ not powering up after repair

[Waynosan]

I went into my x9d+ to to a fix, the only things I disconnected were the battery and the two ribbon cables to separate the two halves of the TX. I've had it open before to fix switches and upgrade to the hall-effect gimbals and never had an issue. Unfortunately upon reassembly the unit will not power on. Battery charger circuit still seems to work cause when I plug in the charger the green LED on the back starts blinking.

Things I've tried:

• Reseated the ribon cables multiple times
• Checked continuity of both ribbon cables (passed, though there were a couple of lines that had continuity in between them, hopefully by design)
• Tried different SD card and without card
• Checked battery (shows 7.8V)
• Connected radio to computer (not detected; doesn't show up in device manager)
• Checked for obvious signs of short like burn marks, smell, etc. (didn't see or smell any)

It's possible that I didn't disconnect the battery when I disconnected the ribbon cables (was my second time in it that evening and I was in a hurry to finish).

Any advice on what to check next? Is there a troubleshooting guide somewhere? Anyone know what lines the voltage is supposed to come across from the rear to the front of the radio?

I found a similar post ("Taranis X9D no power" or similar) on here but it appears to have been the X9D (not plus) version. I'm having trouble finding the components mentioned in that post (admittedly my eyesight is rather poor)

Full disclosure: I posted about this on RCGroups but this forums looks to be a lot more technical so I hope I'll have better luck on here.

[Kilrah]

It's possible that I didn't disconnect the battery when I disconnected the ribbon cables (was my second time in it that evening and I was in a hurry to finish).

This is a well known "proven recipe" for blowing the microcontroller.

[Waynosan]

Yes, I should have known better and confirmed it was disconnected. However I don't know if that was the case for sure and if possible, I'd like to perform some checks to isolate and confirm before I spend money ordering up a replacement.

[MikeB]

If you have plugged the radio, via USB, into the computer with the radio powered off and the radio is not found, then that is a test for the processor no longer working.

Mike

[Waynosan]

If you have plugged the radio, via USB, into the computer with the radio powered off and the radio is not found, then that is a test for the processor no longer working.

Mike

Mike,
Thanks for the feedback. Would you happen to know which pins provide power to the micro? I'd like to check those to see if they have voltage just to confirm it's not a regulator or something upstream.

Also, if I go to order up a microprocessor board, are there any compatibility issues I need to worry about between versions? The board in my radio says "REV0.3". I know there were differences in gimbals and such between a the radios over the years but unsure if electronics changed in a meaningful way.


Update: Mike, I found the other post I was referencing and it looks like you were the one doing helping there:
https://www.openrcforums.com/forum/view ... 97&t=10031

Person was able to fix it. Not sure where these resistors (assumption due to "R" designation) are. I looked for a bit but eyesight is bad and I didn't have a magnifying glass.

[Waynosan]

All right, my mind has just been blown.

So I was poking around in the Taranis trying to compare against the voltages and resistances as in the post that I linked, switching between battery and USB power and all of the sudden the Taranis turned on!!!! I have no idea why because I did absolutely nothing to it aside for probing for voltages and resistances. I've probably cycled the power a couple dozen times prior to that point.

There's still a problem however: I was getting a switch warning on switch SF (my ARM switch) and it was oscillating from open to closed along with the speaker occasionally making a beeping type sound.

I ohmed it out and the switch itself is fine. I traced its input to the right (when looking into the radio up-side down) mainboard connector and when I flip the switch I can close and open the connection between pins 12 and 14 (counting from left-to-right). It's the only switch that does not work properly, everything else seems to be working fine.

Any ideas?

Maybe I should just be happy at this point, move my arm switch to the right side in place of the momentary one that I never use and call it a day.

[Kilrah]

Still thinking your CPU is toast and that radio shouldn't be used again without replacing it or the whole mainboard. Next thing you know it might stop working while you're in flight.

Your choice what your stuff and safety is worth to you.

[Waynosan]

Still thinking your CPU is toast and that radio shouldn't be used again without replacing it or the whole mainboard. Next thing you know it might stop working while you're in flight.

Your choice what your stuff and safety is worth to you.

I plan to still replace the MB, just can do it on a more leisurely timeframe that hopefully aligns with an ebay sale. I'm only flying whoops recently. Will definitely avoid flying anything larger with it.

[Waynosan]

I'm thinking of actually using my reflow station and trying to just replace the processor. The closest available part number I've been able to find that's readily available is STM32F205RCT6.

Would this one work? I'm not sure what the 'C' suffix designates. R appears to be 'reel' and T6 is temp tolerance rating.

[MikeB]

You need STM32F205VE...
The V is 100 pins, the E is 512K of flash memory.

Mike

[Waynosan]

Thanks Mike,
I'm still waiting on the micro to come in but the radio has been working fine with all the whoops since it magically came back to life. Strange.

Thinking of might pick up one of those X-Lites for the smaller form-factor. Not much more than a replacement board for the X9D+. Kind of frustrating how expensive replacement parts are.

Peace