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I agree, my Motorola Service Monitor has a TO-3 zener diode on a huge heat sink protecting its 5 volt supply. Gotta love brute force.

Unplug the SMPS boards and check the resistance to ground of both the 3v3 and 5v0 supply rails on the main board. If the 3 volt rail shows only a few ohms or less there is a high probability that the

I accidentally fed 26v to my QMX. That's what I get for keeping too many running projects laying around, especially when they require wildly different voltages but the same plug format. Next time I'll

First time installment of a firmware on a new QMX (no EEPROM file) will not initalize all menu settings correctly. In the menu the keyer setting defaults to straight and tip. Change it to to e.g.

If you're interested in ordering the?VIFLY ShortSaver you might as well order them directly from China via AliExpress and save some money. I ordered some from?VIFLY Drone thinking that I was helping

How about just using an attenuator with a bypass for receiving? QRPGuys have one for 25 dollars or so. Don Meyerhoff WA2SWX

Oh, yes, that was a nice trick.? I figured out the problem with 15m is that the cutoff frequency is too low, and 21.074 MHz is actually more than 3dB down.? I did the transmitter test at 19MHz, well

I accidentally plugged in a 26v supply from another ongoing project. Do you suspect I'm ok after replacing the SMPS boards or is this disaster likely more serious?

Thank you very much for the information. Now I can proceed with the assembly with peace of mind.

Thank you for your thoughts and clarifications! The more I play in Elsie with LPF simulations, the more I agree that following the manual will be a good start. It seems in the QDX HB, the 15/17m LPF

http://qrp-labs.com/qmx/qmxtrouble.html "The current assembly manual is correct: C525 is 270pF and C516 is 180pF. " Be careful, simulations must account for stray capacitances. 73 Alan G4ZFQ

On the QMX rev.2 PCB, it appears that the values of C516 and C525 are swapped between the schematic and the manual. I have run simulations and the values in the schematic seem to be better. What do

You can adjust input gain in the terminal configuration menus. 73 -- David Thomas M0OOR

?? I agree! -- 73, Barb

ROFL... and we can celebrate this fine Tuesday with one less mystery to worry about! 73 Hans G0UPL http://qrp-labs.com https://www.buymeacoffee.com/g0upl

I have used numerous ProgRock2's without any problems -- I install them in old receivers and transmitters to replace faulty/drifted crystal-based heterodyne oscillators.? What are you trying to do

Did you made the output transformer in the WSTS style? 73, Ludwig

Hi Nate From Material 17 I used the size 30 (T30-17). Validation by using T37-10 showed two things: 1. My setup brought probably to high values for L. 2. Despite the deviance (see No 1) the AL of the

You are right Hans! I forgot to mention the most important point! I lower voltage to 5V! Getting old!! Sorry for the snafu! -- 73, Barb

Hello Barb The maximum power dissipation of a BS170 according to the ON Semi datasheet (these are the devices we supply) is 0.83 Watts. If a QCX was producing 5W output at 60% efficiency the heat