Hans, i blew up my QMX IC 203 . I stole one from my other kit and installed it.
?I also order two more qmx's

I ordered 2 spare, STM32F446VET6, chips from Mouser Electronics in hopes of fixing the blown radio, but got to thinking, I might need a boot loader to load the firmware.? am I correct. and the chips will not work?
?Thanks,
Vernon Franklin
AA7HC

I've been wondering the same thing Hans.

开云体育

I’m going to guess that it will not work without the boot loader.

On Sat, Sep 30, 2023 at 06:17 AM, William Smith wrote:

Hans has previously stated that he is not releasing his software.

Perhaps he could be persuaded to sell replacement MCUs with firmware installed.? In this way he could make some profit, help his customers and still retain control of the firmware.
73, Don N2VGU

Don,

I believe that you need the board to supply the power and connections.? I understand that he is loading each board after receiving it at his QTH.? I would guess that a jig could be made.? The cost and complexity would make it almost as expensive as buying a new kit.? An alternative would be to sell just the mainboard with the processor preprogrammed.? The customer can remove the chip and use it to replace the failed chip.? That seems risky for little gain other than not rebuilding the kit.? I would opt for a new kit.

My opinions and speculations.? I know I should not speculate on this forum.? Apologize ahead of time.
Back to lurking.
73
Evan
AC9TU

On 30/09/2023 16:02, Donald S Brant Jr wrote:

he could be persuaded to sell replacement MCUs with firmware installed

Don,

He has already said that is not possible. They come on the boards then he loads the bootloader.

73 Alan G4ZFQ

My 2 cents worth here. ?I’ve often found if the cpu is blown, many other chips and some caps are blown as well. ?In one case I had a QMX for repair that I got all working except for one bad pin on the cpu. ?I de-soldered a cpu from donor board, de-soldered the bad cpu, cleaned up the good cpu and soldered the good cpu onto the board. ?It all worked fine. ?But that was a rare convergence.

Well? thanks Hans for the update.
?I can make ear rings out of the new chips when they arrive. Someone geeky will wear them. Not Me!

Google QFP100 socket
Numerous hits, most are under $100.

says it's good for the low-profile LQFP form factor.

I hate to see people writing off their kits as unrecoverable after an accident, just because a replacement microprocessor is unavailable.? A lot of work goes into a kit build before it gets damaged.

The idea that most hams are unable to do the microprocessor swap isn't necessarily a definitive answer as to whether QRP-Labs should offer replacement, programmed parts.? I think it would be perfectly fair for Hans to say "Attempt replacement entirely at your own risk".? Maybe only sell to people who had previously bought a QMX kit.? And anyway, one ham with the "mad skillz" to do the work could repair other peoples' boards.? Looking at you, Jeff Moore.? Thank you for your work on other builders' fried radios.

Changing the STM32 isn't quite trivial, even with a heat gun.? There are a number of SMD capacitors on the other side of the board, C205-C216, and they're not all the same value.? So if they start falling off you have to gather them back up, measure them to sort out which goes where, and reinstall them after the STM32 is replaced.? I think they'd stay in place (surface tension if/when the solder melts) as long as the board isn't jostled while hot.? Jeffrey Moore has shown that it can be done.? (Jeff, did any capacitors fall off of the board when you did it???? Let's hear from the voice of experience.)

It looks do-able.? Lots of room around the STM32.? I've got a heat gun... (laughing).? So now I'm eager to build up my QMX so I can get it running, and then remove and replace that STM32 ... and see if it still runs afterward.? I'm not going to say I can do the replacement until I've done it.

I have not used this one, but I do use smaller ones from the same company to make prototype circuits.?

?

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?

--
Colin - K6JTH?

On Sat, Sep 30, 2023 at 12:27 PM, Hans Summers wrote:

I suppose sockets do exist??

They do, apparently:??
It might be a high-margin line of business for you and the folks who DO have the ability would appreciate being able to make the repairs; there are several such folks on this forum.
It would sure be more Earth-friendly than binning an otherwise-functional radio.? Everyone wins.
73, Don N2VGU

It just takes me a couple hours to wind and install the toroids. That is the only issue I have building another board. Fat Fingers are the main issue. But it is still alot of fun building.? I wish I had the patience to actually understand everything design something.
?Thanks Hans, for all the great work and awesome kits !

Great.,? I can possibly repair two radios someday.? I won't trash them yet.?

I would be willing to help out.? Just send me a PM.

Here is what I do to replace the cpu. ?Keep in mind you need a programmed donor cpu for this. ?I always get very anxious when I use a heat gun with lots of small parts around the target. ?I’ve used this technique successfully but I prefer the low temperature solder method. ?I put a bead of flux & a bead of low temp solder around the entire chip, I keep circling my iron around the chip until it is completely loose. ?I then pick up the chip with a vacuum pen. ?I clean up the board with solder wick. ?I clean up the chip by solder wick under the pins on a silicone heat proof mat. ?When installing a new cpu, I line it up carefully, tack solder one pin, straighten then tack solder another pin. ?Once all is lined up perfectly, I solder each pin by hand very quickly. ?I have a really small iron. ?Some pins (like GND) won’t flow well. ?I then get a bigger tip and reflow those stubborn pins.

it’s great when you turn it on and it comes to life.

good luck,
Jeff
W1NC

On Sat, Sep 30, 2023 at 08:41 PM, Jeffrey W Moore wrote:

I prefer the low temperature solder method

Thanks, I am glad to hear your opinion and your description.? I decided to try the low-temp desoldering alloy rather than the hot air gun for the same reasons.? Much gentler on the board, and there's no worry about capacitors dropping off the other side.? Since the STM32 is QFP (pins), not QFN (pinless), we have access to all the solder joints.? That's a big benefit ---- Thank You Hans for choosing QFP rather than QFN!

Jeff, I am NOT at your level of skill and knowledge for diagnosing and fixing busted radios.? I just want to see if a monkey with a soldering iron can pull off this repair without damaging the chip.

I need to know my QMX actually works before I start messing with it, so it's time to build the thing.? I'm a slow builder, but I'll eventually report back here.

And THANK YOU again Hans, for hearing our plight.

All of the desoldering methods will work better if background heat is applied to the board by e.g. a hot plate.? It needn't be excessive, even "just too hot to touch" will make a marked difference.??
I generally set mine to 100°C or so; even if the board is not making intimate contact it will heat up fairly quickly but the temperature will remain low enough that parts are not going to come off.
73, Don N2VGU