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My C510 is also marked 103, which is 0.01uF, as you mentioned. I can confirm C510 is listed as 2.2uF in the assembly manual. That said, my QMX works fine. Would it work even better with the specified

Hi, Can anyone confirm somthing for me on my QMX build.? On the power supply board the central one with 3/3 pins. Looking down onto the plug when it is plugged in, is the centre pin conted to Q101

Ok, looking more closely at both, my Q103 is clearly further away from Q104 than Giuseppe's is. So Giuseppe, be careful and be extra sure there's no short between Q103 and Q104!

Q103 and Q104 can look close, but still be ok. There's close and then there's too close. Mine pictured here are fine, no problems.? Q103 is centered on its pads. Although the tab extends off the pad

Pathway for receive is exactly what I thought! But C510 being marked with "103" means 10 + 000 or 10000 pf = .01μf... right? Parts says 2.2μf. That marking should be "225" or 22 + 00000 pf = 2200000

If you look at the TAB of Q103, it looks like it's sitting on one of the contacts of Q104. Looks like you need to move Q103 away from Q104-- The short is to the pad of Q104, there's no way moving Q104

It looks like C509 is a crucial pathway for RX_In

Got that pin soldered that I left un-soldered after misunderstanding the instructions. Have found a missing part! C509 is not on the board. C510 is and it is a 0603 sizes SMD marked "103." C510 is

Thinning the herd a bit.? Offered for sale is my QRP Labs QCX 40 meter CW transceiver. This is the "classic" model. Firmware is at version 1.08. Transceiver is mounted in a Ba-Ma-Tech aluminum case.

Karl, THIS MIGHT BE IT: *Make sure your QMX is set to VFO A before performing the RF sweeps.* If it's set to VFO B, the RF Sweep doesn't work right and shows graphs like you posted. Yeah, I just had

From my experience swapping them made it worse. I used new capacitors so their values may have been not exactly the same as the originals, but they should have been as they were marked correctly.

Karl, there is one more fix for you to make. Refer to http://qrp-labs.com/qmx/qmxtrouble.html the section *Low 20m output power on early QMX builds* Capacitors C525 and C516 values incorrectly swapped

Dan, When you have IC403 removed, check the voltage at the junction of R401 and R402, in both receive and transmit. It should be 2.5V in both cases. If you have a short at one of the bandswitch

Indeed that sounds like the QMX issue I see. However it does not happen on the QDX, ONLY on the QMX. TRY reverting to firmware 006 and see if it fixes it. If so then you have exactly what I see with

I found the culprit! I had the screw securing the corner power supply board too tight, which caused the body of inductor L101 to contact pin #3 on the LCD board. Backing off on this screw just a

Hello Reiner, Did you use all the values of the low band LP filter 20/30 for HB-QDX?? Were you able to look at the harmonics from this modification?? I did not make any changes to my HB lpf and the

This looks very similar to the issue with FT8CN /g/QRPLabs/topic/100738548#107806

Regardless, do ohm check between drains Q103 and Q104. The easy way to check this is ohm between Gate and Drain on Q103. Good is about 50k ohms. Bad is zero. 73 Karl KI4ZUQ

Same here with linux and FLDigi. Initial? PTT gives a very short burst of power out, then no modulation but keying continues to work. reset QMX and above repeats. 73 Kevin K3TL

I have one high-band QDX and need another one.? I'm looking for a QDX-Labs assembled unit, rev 5, 12 Volt, perfect working condition. Best, Jim K8DDV