Topics

QCX-SSB Troubleshooting

radiodoc43
 

Was very excited to finish assembling my second QCX as a QCX-SSB, by following the wonderful assembly instructions provided by DL2MAN. Everything went well right up until connecting the completed board to power prior to uploading the boatloader from an Arduino UNO board. I let the smoke out of the finals a few seconds after power was supplied. 

Obviously, it is likely that I made a wiring error, but the thought occurred to me that the initial power-on was with the provided Atmega chip, which I assume would try to initialize the board, not knowing that it is a completely different circuit. There was no dummy load attached at the time. Is it possible that the installed software could be to blame? 

I am looking for some guidance on how best to proceed. I don't want to replace the finals and have a repeat experience. 

Can I remove the finals Q1, Q2, Q3, then install the software and then replace the finals afterwards?

Any suggestions would be appreciated.

Craig

Ryan Flowers
 

I don't know the exact answer to y our scenario, however I would definitely attach a dummy load before powering it after you replace the bs170's. Thankfully they are cheap! :) 

On my own build, I noticed that during firmware update (with the Arduino Nano attached) it went into TX mode, and they got VERY hot. I caught it and attached a dummy load before the magic smoke was let out. 



On Mon, Jun 1, 2020 at 5:32 PM radiodoc43 <Monsen.Craig@...> wrote:
Was very excited to finish assembling my second QCX as a QCX-SSB, by following the wonderful assembly instructions provided by DL2MAN. Everything went well right up until connecting the completed board to power prior to uploading the boatloader from an Arduino UNO board. I let the smoke out of the finals a few seconds after power was supplied. 

Obviously, it is likely that I made a wiring error, but the thought occurred to me that the initial power-on was with the provided Atmega chip, which I assume would try to initialize the board, not knowing that it is a completely different circuit. There was no dummy load attached at the time. Is it possible that the installed software could be to blame? 

I am looking for some guidance on how best to proceed. I don't want to replace the finals and have a repeat experience. 

Can I remove the finals Q1, Q2, Q3, then install the software and then replace the finals afterwards?

Any suggestions would be appreciated.

Craig


--
Ryan Flowers - W7RLF
MiscDotGeek - QRP and More

ajparent1/KB1GMX
 

I strongly suggest programming the 328 in a separate socket off board
or in a Arduino Uno.

You have no certain controll of all IO while programming and bad
stuff should be expected even if its not supposed to.

Allison
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Please reply on list so we can share.
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radiodoc43
 

Thanks all.

Making progress. Removed finals. Two had lost their smoke. Left them all off board for now.

Managed to load software using Arduino Uno board as described in assembly manual. (Had to edit avrdude.conf file for non Atmega 328P chip error. (Replaced 0x1e 0x95 0x0F with 0x1e 0x95 0x14)

Success! Now I have a receiver.

Will plan to replace the BS170's in the final and see if it is a transceiver.

Noticing lots of intermittent clicks on receive. Also, the audio seems a bit distorted, with a low intensity heterodyne heard on sideband and AM. Not sure if this is due to the lack of the FETs in the output stage or something else. CPU states running around 81% with roughly 56000 samples. Don't know if this is normal.

Continued hand-holding appreciated.

Craig KC2LFI

Manuel; DL2MAN
 

Hi Craig,

The clicks on RX were recognized by us (Guido and me) too, recently. We´re still looking for the cause of this behavior. 
Also the distorted Audio is (unfortunately) normal @ Volume 16 right now. (V1.02d)
Use Volume 15 and below for now. Future Updates will hopefully solve those issues and provide more dynamic range for the AGC, and limit max AF Volume to below that value it starts distorting.
But missing PA Fets contribute nothing to the behavior of the receiver.
In fact I also have blown them already twice in my Class E experimentations ;) It´s easy to blow them, because they are rated for 60V, and if you have wrong "load" = mistuned antenna, mistuned LPF, or nothing at all while TXíng (which is worst mistune possible) those BS170´s face more then 60V. Only a few seconds of mismatched TX, and they´re gone......

73 Manuel; DL2MAN