Hi gals and guys!
It's my fist message on this forum, so please let me that Hans is doing a great job with QRP Labs with his fantastic products (QCX-mini, QDX and QMX to name just a few).
Recently I've purchased high-band QMX rev. 3 and found some time to build it. Except for a few small stumbles (eg. non working buttons) I would say it was a successful build. Just a few days ago I had pretty decent sweeps (audio, RF, LPF and SWR) for all the bands except for 15m and 17m. I thought it may be some continuity problem with the T508 and T512 so I reworked the solder joints, put the radio together and... I lost TX and RX capabilities. This means no power output (on the "Diagnostics" screen after pressing T) and totally random test sweeps for all the bands: audio charts show no LSB/USB separation, RF filter shows random values around the middle part of the chart, LPF chart goes steeply to 0db on the lowest frequency and stays there until the end of the range. When I connect an antenna and power meter, I get 0W reading on transmit and barely can hear other stations (the signal is very faint). "Input Analysis" screen shows "NO SIGNAL".
I didn't touch anything else - the LPF toroids for 15m and 17m were the only thing I reworked. So I inspected all the solder joints and connections on the PCB multiple times, fixing the ones that weren't looking good enough, but it didn't help.
When transmitting, the power consumption goes from around 0.1A to 1.1-1.2A and the BS170 get warm. That's a good sign, isn't it? ;)
Any ideas what I should do next, keeping in mind I don't have any oscilloscope (just a regular multimeter and nanoVNA)? Do you have any ideas what may be the cause?
I really hope you can help me...
Have a great day,
Damian SP9LEE
