Last Easter I built a 5-band QMX and although I found it quite a challenge, it worked from the get-go and I was really pleased with myself! I get a lot of pleasure from building electronic kits and this will be the sixth one from QRP-Labs.
My only gripe about the QMX build was that the design left the components incredibly tightly crammed in, and I wondered why they hadn't made the PCB just 10mm wider. But since then, I have read Hans Summers' document explaining that, for him, it was a design-challenge to come up with such a compact design. Well, he did an amazing job!!
Anyway, here we are a year later and I see that Hans has released the QMX+ transceiver kit. This time, the design has much more space between components and I'm anticipating that the build will be far easier than the original design.
So what is a QMX+?? Well it's a high quality 12-band MultiMode (CW/DIGI) Transceiver which can be purchased as a self-build kit or as a pre-assembled unit - it's worth noting however that there is a very long waiting list for pre-assembled units - maybe up to 6 months 😮
In terms of functionality, the "PLUS" version is little different to the standard QMX but it has the advantages of being able to house a GPS unit, an SWR Bridge, a Real Time Clock (battery backed), a Developer's Kit and maybe even an ATU in the future. Hans also has other "secret" plans for the ongoing development of the QMX+ including SSB Mode which will be awesome!
I feel (and I may be completely wrong) that the QMX+ is a big step toward the release of the fabled QSX which will be an All Mode transceiver with who knows what features.
I currently own a couple of (tr)uSDX transceivers and these are simply amazing little radios which are multi-band, all-mode SDRs with built-in sound card, speaker, mic, keyer, PTT, etc. But their performance is far from perfect. Don't get me wrong - I love them - and when you're up on a hillside playing POTA or SOTA, their performance will bag you many contacts for little outlay. But they're just not in the same league as a QRP-Labs product.
I'll always remember when I built my first QRP-Labs kit - the QDX. It went together well and it performed superbly!! I was getting better results on my 5W QDX than my Multi-Watt IC-7300. I was (and continue to be) very impressed!
Sorry - I'm rambling. Let's look at the QMX+ Kit. It arrived in a single box which contained all the relevant components, each type being bagged separately. I'd also ordered the optional GPS Module plus (of course) the metal enclosure.
The quality of this kit is extremely high and I've yet to come across a QRP-Labs kit with missing pieces. The aluminium case is strong and well finished, with sharp text on the end plates.
The Assembly Manual for the QMX+ is extremely good (as usual) and I intend to follow the instructions to the letter, just as I've done before.In addition to having access to the manual electronically, I also decided to print a copy so that I could read through it prior to starting the build and highlight bits which I think warrant special attention, making notes in the margins of the page. I also use the printed manual to mark off each completed section.
I had decided to do this build at the weekend while I was at our caravan - nice and peaceful with no distractions. Prior to going there though, I wound all the toroids and then bagged them individually in tiny sealer-bags with ID labels.
All pretty straightforward but the most tedious was L506 |
Before starting the build, I laid out all the components and marked off the capacitor values. Once that was done, I fitted the caps, the diodes and the inductors. Very simple.
After that I installed the BS-170 transistors, clamping them in place before soldering.
Next up was to install all the toroids and the trifilar. Since I'd pre-wound these, it was a breeze to fit them all and once I've adjusted them as part of the 'tuning' procedure at the end, I'll probably drop a few blobs of hot-glue on them to keep them secure when the radio's in transit.
At this point of the build I realised that I was rocketing ahead and was being a little blasé, so I purposely slowed down and checked everything I'd done so far.
You will soon notice that some of the solder-pads are TINY and it can be real difficult to get the tip of your soldering iron onto both the pad and the component at the same time. If you look at the adjacent image, you will see that some solder-pads are way, way smaller than others and some of the pads are barely visible. This is a multi-layer board and the ground really sucks the heat from your soldering iron, so make sure you use a decent one that can cope with it.
Diagram From The Manual |
In the hope that it will help others, I have redrawn this and although it makes sense to me, it may not to you 😂....
With everything installed (don't forget the link under the GPS Board (if you bought one)), it was time to slide the PCB into the lower half of the enclosure.
I checked and double-checked the pcb for any obvious signs of faults such as dry joints, solder shorts, etc, but there was nothing obvious. I could see 9V at the power switch.
I sought help on the Groups.IO forum and got nowhere initially, so I submitted a trouble-ticket at QRP-Labs but six days later there was no response from that either.
It's extremely disappointing when stuff like this happens and I know there's bigger problems in the world, but neverthless I'm feeling quite disappointed considering that I've successfully built 5 other kits from Hans (including the regular QMX which is much tougher build) and a few from other kit manufacturers.
A few days on and members of Groups.IO started to make suggestions and I learned that there should be voltage at Vcc and Vdd but there was none on mine. The thread got busier and someone suggested that I try swapping out the Power Boards from my QMX to my QMX+. To reduce the risk of damaging anything, I was using a variable voltage/current PSU. With it, I could reduce voltage to maybe 7.5V and 200mA.
Before swapping out the boards, I recalled my soldering struggles and decided to reflow virtually all the connections to make sure that I'd not got a bad joint somewhere which was causing these issues. The Ground Plane on this pcb really does suck the life out of your soldering iron!
I decided to remove the power boards and the GPS module. It was then that I discovered I actually had a short on Vdd. No amount of probing with my DMM helped discover the source of the short, so I’ve given up for now.
I’ve approached an electronics professional friend to see if he can afford the time to do some fault-finding for me. If not, I might have to order another and start all over again 😪.
Part-2 to follow!
Regrettably, my friend is in the process of moving to another country(!) so I'm now proper stuffed 😂 I guess I'm going to have to write this off completely.
On a more positive note, G4GIR very kindly offered to look at the board for me, so I've popped it in the post to him and await his verdict. Let's hope it's nothing I've done 😂😂😂
Ian G4GIR has carefully examined the pcb and has determined (with the very kind help of Jeff Moore W1NC) that the fault is with the main CPU, so that's nothing to do with me or anything that I've done wrong. In fact, Ian complimented me on my construction work.
73, Tom, M7MCQ.
PART TWO of the build is >>> HERE <<<
This next post shows how I completed the kit and shows the final outcome 😊
6 comments:
Good afternoon Tom that is great news and good on Hans for sending that to you! By building this kit you are getting lots of hands-on trouble shooting. Looking forward to reading more!
73,
Mike
VE9KK
Any updates with the new pcb, Tom? I have now finished construction of my QMX+ but have not yet applied power - hopefully this evening after a busy planned day of yard work.
73,
John AE5X
Hi John, funny you should ask because I’ve JUST finished rewinding the toroids and I’m ready to start work on the new PCB. I’m off work for a week (at the caravan) so it should be finished this week.
Before I add a single component to the new board though, I’m going to test it by connecting it via a USB cable to a PC and then using a 3.3V 200mA supply to a Vdd point to make sure the QMX shows up on the computer as a flash drive. Once that’s out of the way, I’ll crack on with the build.
Watch this space, LOL. Good luck with your switch-on!
73, Tom, M7MCQ.
That's interesting - you can power it up before beginning construction! Makes sense since all of the kitted components are for RF, not the PC-radio bits.
My power-up didn't go so well either. It transmits ok, but no receive. I wish I still had an oscope...
73,
John
Anonymous has left a new comment on your post 'QRP-LABS QMX *PLUS* PART-1':
Hi John, I missed out an instruction all together - no idea how it happened - just glad I finally spotted it.
There’s a tiny link to be made just above T507 - it’s on Page 37 of the manual in bright red but somehow I managed to skip it altogether.
Just wondered if same happened to you.
Tom, M7MCQ.
I had exactly the same problem with my 1st QMX+ and traced it to a CPU fault. I didn't try complaining though, just bought another kit. My second build works great - have made many amazing qso's with the rig so far. I've seen your post about your PUTTY plots - happy to swap notes if you reach out - I'm good at qrz.
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