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STM32 dead

  

QMX bought all assembled 3 weeks ago and a few QSOs without problems.
And suddenly it doesn't restart. After investigation, the +3.3 V has a short circuit. After removing the doubt about the components connected to the VDD, it turns out that the 3.6V zener diode D109 is short-circuited, despite everything, once the diode was removed, the short circuit was still present.
 I deduced that only the STM32 remained. I put it down and the short disappeared. I ordered one from Farnell. Now I wonder if it will be possible to reload the software without difficulty because I read that it was a question of bootloader.
If anyone can enlighten me on this point, thank you in advance.
Gérard / F6EHJ
 

Mentioning a model would be good
You'll most probably need to order one from Hans instead
BUT
It's very unlikely the CPU killed the diode
It's more? likely the diode died trying/failing to save the CPU from too many volts

I'd strongly recommend working out what you did wrong before doing anything.? ?e.g. intermittent power supply connections, wrong voltages and poor power supply regulation? generally have been an issue for some models? in the past.?
Unless you know? /fix the cause it can all happen again just as quickly.? ?CPU Replacement is tricky so you wouldn't want to do it twice
 

On Sun, Jan 12, 2025 at 10:10 AM, <f6ehj@...> wrote:
diode was removed, the short circuit was still present.
I had the same symptom on my build of the QMX+. ?
It was during initial testing after build.
I was operating the unit from my bench power supply in a current liming mode.
I think it was set to 200ma max, (whatever the manual recommended).
Everything seem to be working fine and then it went dead.
I noticed the current was at max, where it was operating around 80mA.
I quickly powered it off and noticed one of the power supply board was hot. (don't remember which one)
I inspected the board for a solder ball rolling around but could not find anything.
Turned the unit back on and it powered-up fine.
In further testing I found the receiver was deaf. : (
?
(I ended up sending it to a gentleman that Hans recommended and he replaced the A/D)
When he received it however, he said it would not power on.
His inspection found a solder ball under the CPU, (between the actual chip and the solder pins).
He said it was fun getting the solder ball out.
Might check for that.
Good Luck!
?
Albert
KE0PRX
 

f6ehj via groups.io <f6ehj@...> wrote:

I deduced that only the STM32 remained. I put it down and the short
disappeared. I ordered one from Farnell.
the QMX and QMX+ (I assume we're talking about QMX), and it's guarded by
him (not distributed as a file to be loaded). This bootloader is then used
to load the firmware downloaded from the website, and the firmware itself
is encrypted in some way (so only this bootloader can decrypt and flash
it).

This ensures that the firmware can be loaded only onto boards bought from
Hans (makes it more difficult to make and sell clones).

If that's the case, then you won't be able to use the STM32 you ordered...
 

Adam via groups.io <qrp-labs@...> wrote:

I deduced that only the STM32 remained. I put it down and the short
disappeared. I ordered one from Farnell.
the QMX and QMX+ (I assume we're talking about QMX), and it's guarded by
Something went wrong. There was another line here: "From my understanding
(correct me if I'm wrong), the STM32 shipped with".

I guess starting lines with "From " might not always work (it's a message
separator in mbox format)...

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