Fellow Ham's QCX+ 5W CW Transceiver - 40m

Bob, KB0**^[1], contacted me in mid-March, 2021 with an interesting project – could I repair his QCX+ kit? Bob and I had talked some since having the original QCX kit along with having a pretty fair background as an Electronic Tech and Engineer^[2]. I stopped by Bob’s place later that day to see what the challenge would be. Bob explained the kit that I was looking at was really the second one. He further explained the first one was partially destroyed trying to remove some incorrectly installed components. Silently, I thought this second one was probably not looking to be much better. I asked him what parts were left over, or from the first kit. He mentioned that he threw out the first kit’s main board, but still had some of the parts. At least there was something to start with in hopefully resurrecting the kit.

After getting it all home and taking a more detailed look at the kit such as what had already been done along with what parts were available, the following initial assessments were made:

• The Main Board and the (assembled) Display Board were seen to have quite a few issues such as bad soldering, blobs of solder in many places, quite a few printed circuit board (PCB) pads seeming to be “burned off”, missing components, and wrong components installed.

• There were quite a few components in the box of parts. At this point, I was not sure of having enough of everything or what may be needed for any repairs, but it appeared that there was a sufficient amount “just in case” something was needed.

• A mostly unassembled Display Board along with what seemed to be the right parts being in the parts box to assemble a Display Board.

After getting Bob’s kit and seeing the challenge ahead, I really thought of just ordering a new kit (for USD$55), assembling it, and then “gifting it” to Bob. I like Bob – he is just a great person to know. The decision was to hopefully resolve the issues being seen.

The kit’s repair process started around the third week of March, 2021 and successfully completed on 18MAY21. The duration between the start and the end was due to getting a few parts in, ordering a desoldering gun (Hakko 301 as described below), two of our four single adult children visiting my wife and I over two separate weekends, and a bit of travel that my wife and I did.

^[1] The name and call of “Bob” and “KB0**” are fictional and being used to protect the actual person’s identity.

^[2] Many years ago, 45 is more approximate (between 1976 to 1978), I was a Technician at the GE Medical Circuit Board Plant in New Berlin, WI working full-time on the midnight shift (from 11pm to 7am Sunday night to Friday morning) while concurrently enrolled at the Milwaukee School of Engineering in their Electrical Engineering Technology program (taking 12-16 hours per quarter). It was tough going to school and working. I gained a great deal of experience resolving new boards that had failed for some unknown reason(s) from a day’s production runs. Several other Techs and myself fixed those failed boards getting them back into their production lots. After a while, I typically wound-up getting the new ones what I silently termed “the b!+ch boards” at first due to their complexity and destined for assembly into the (then) new Computerized Tomography (CT) units. The problems encountered ranged with bad solder from the wave solder process (seemed to be a recurring issue when coming in on Monday evening getting boards from that day’s first run or two after the wave solder being fired-up from being off all weekend), components not right or missing, along with a just a ton of weird and convoluted issues. The end result was getting just about any failed board fixed.

Prior to GE and returning to college, I was a pretty good ECM Tech fixing airborne ECM receivers to the component level until getting out the USAF and going back to school (I was drafted in SEP72 while in college enlisting in the USAF several days later).

I also “touched up”, repaired, redid circuit board traces, and/or “rewired” my prototype digital, analog, and/or RF PCBs or module designs as an Engineer in Receiver Systems Development at E-Systems, Inc., Garland Division in Garland, TX from 1983 to 1989. The prototypes were design proofs prior to finalizing the electrical and mechanical designs for release to manufacturing.

The first thing tackled was assessing the assembled Display Board finding the following:

• Soldering – blobs of solder

• Burnt-off pads and traces leading to pads. The ones that appeared to be missing and burnt-off were the pads going to the two (2) 2x3 female headers (JP2 and JP3).

• Incorrectly installed parts (i.e.: switches tilted (S2, S3), 1x16 male header installed backwards, and 2xnn female headers installed on wrong side of the board (as mentioned above))

  • Uninstalled part (R46)

  • This was determined to be the Display Board from the second kit that was ordered (replacing the first one)

The second display board was in pretty good condition although noticing the following:

• Incorrectly installed parts (i.e.: 2xnn female headers installed on wrong side of the board). What appears to have happened was the single female 2x5 and the two 2x3 headers being installed on the wrong side of the board (they were soldered-in facing the front when they should have faced the rear). My guess is they were noticed as not having been installed correctly, then attempted for unsoldering along with removing the headers’ housings. Since having a solution for the female headers, the remaining housing was removed and then the connection points desoldered.

• I figured that assembling the Display Board from the mostly bare display board PCB, display, and parts was the better option than trying to repair burnt-off pads located just slightly under the soldered-in display with the assembled Display Board as received. So, I assembled the Display Board using the parts in the box along with a few from my parts (i.e.: the female headers).

Wow, where does one start with listing the variety of issues? As with the Display Board (above), the Main Board’s PCB had some similar issues along with some unique ones:

• Soldering – blobs of solder all over the place

• Burnt-off pads and traces leading to pads.

• Wrong parts installed. This was mostly wrong value resistors having been installed. Most were located after doing a mostly complete visual inspection comparing the value found in a location on the board to that what it should be per the schematic and the parts listing. Admittedly, I did manage to miss a few, ones that would be found later when troubleshooting a stage that was not appearing to working correctly and noted later when located/discovered.

• Incorrectly installed parts

• Uninstalled parts

• Toroids – T1 and Low Pass Filter

After having a good inspection of the component and solder sides of the mostly assembled PCB, I decided to completely desolder the board for two reasons: too much solder just about everywhere, and I needed to ensure there were no other burnt-off pads, traces leading to pads, and especially pads that may have a problem hiding under the globs of solder. Plus, I wanted to ensure that good solder was being used (since unsure of the current solder’s pedigree).

I was definitely not going to use “solder wick” or a manual trigger-type “solder sucker” to remove almost all of the solder on the main board. Doing either of those methods would have ensured a sure death of the board destroying more pads using a lot of heat and longer heating times trying to get solder removed. So, there was a delay for about a week while ordering and then receiving a new Hakko FR-301 Desoldering Tool (wow, have been wanting one of these for many years never justifying the price). Getting the Hakko FR-301 made the desoldering task near effortless getting the board cleaned-up very quickly (about 15-20 minutes from start to finish) and no damage – definitely the tool to use! It has been used more and more ever since receiving it!

First “power on” commencing the testing phase was on 20APR21. The QRP Labs Dummy Load was connected along with an earphone. All seemed to be good when initially powering up such as with the receive current draw. The first thing noticed though was nothing being heard in the earphones – not even a background hiss regardless of the volume setting. Something, or somethings, were amiss! More discovery was ahead!

Several issues were found fitting the assembled Display and Main boards into the enclosure. The first was the board-mounted 1/8-inch (3.5mm) phone jacks were each cocked slightly where they would line-up to enter the rear panels holes (as shown below). I also had to modify a nylon M3 nut by cutting off one side so that it fit next to the Volume control, R1, when the Display Board was fit to the enclosure’s front panel (not shown).