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Hello Devan A technique I suggested for QCX troubleshooting was to bypass the signal generator resistor (120K in QCX, 100K R518 in QMX) with a much smaller resistor, say 330-ohms. Then the signals

Thanks, I'll try that as well. -Jerry AC5JM

I have a TTL to RS232 converter that was designed to interface directly with Raspberry Pie I/O pins that I will try and let you know.? It should also work in reverse to convert RS232 to

Hans, The trifiliar was one of the first things we did…. Also, I reflowed all the other places where enamel comes thru the board. I should mention that the 1804 gets warm… not hot but warm.

Wayne, I had it lying around from a Raspberry Pi 3B that I had put in a different enclosure with different cooling so the heat sink wasn't needed anymore. Wish I had more of them. 73, Cliff,

Hello Devan The fact that it has noise along there, not flat-lined, indicates to me that the PCM1804 is probably OK. You probably have an issue upstream of that. Could even be toroid enamel... or

RF Filter Sweeps

Image Sweeps

Audio Filter Sweeps

Thanks, Cliff. You've been a tremendous help on this. Where did you find the heat sink you have on top of the finals? Wayne KB4DSF

Hans, The sweeps were terrible. And I have no audio out of the 1st QMX. I worked with John Zbrozek a good bit with the 1st unit and we got it that far and we decided that the PCM1804 was likely bad.

Have you tried the power boards one at a time from the old unit that does power up in the new QMX? 73, Cliff, AE5ZA

Wayne, There is just a hole through the plate to hold it in place and a foot that you can't see almost at the left hand edge under the plate the same as the one that is visible on the right hand

The BS170 (finals) are low power devices with a thermal impedance of 150C/W.? Trying to reduce the internal chip temperature by lowering the already low external thermal impedance is pretty

Hello Devan There's only one ADC on the main board which is the PCM1804. But I'd suggest first checking what you see on the RF sweeps (apologies if you've already posted that here, too many topics to

So I think the discussion about pin headers for the PA transistors is adventurous. The most important point with all devices QCX, QDX and now QMX is absolutely the use of a tuner. The antenna needs to

Good morning, I have received and built my second QMX according to the current build guide, and cannot get it to power on. I built it for 12v operation and I tried starting at 7v and then up to 10v

Adam via groups.io <qrp-labs@...> wrote: Nevermind. I had short on an RF port.

Hi Bojan Awesome Well it was all about romance. Marriage. Of QDX and QCX-mini. For whatever reason, I was determined to make it all fit in the same enclosure as QCX-mini. And use through-hole

Hey, Cliff. How did you mount the plate under your finals? Wayne KB4DSF