Hello all,
I just finished building my first QRP Labs project, a QCX-Mini for 10 meters.? I am new to this group and this is my first post.? Is this the appropriate group to discuss the QCX-Mini?? If so, read on, if not let me know and I'll cease posting here.? It transmits fine, about 3 watts or so which is what it should be for 10 meters.? I also ordered, wound, and installed the 10 meter LP filters L1, L2, & L3 according the instructions provided and I was able to peak the output power with C1.? I also followed the provided instructions to wind the T1? transformer and the L4 coil for 10 meters.? Unfortunately the receiver seems to be quite deaf.? There is a constant rhythmic chattering tone in the earphone.? When I go through the BPF alignment process the internal frequency generator tone can only barely be heard but not peaked.? Also the volume control has no effect on the 2-digit indicator on the right top of the display- it stays at 00.? When aligning IQ, Low, and High, the 2-digit volume indicator increments and decrements as you turn the volume up and down but adjustments of the appropriate potentiometers has no effect on the signal strength indication bar graph meter and the signal strength indication constantly fluctuates erratically up and down without any help from me.? I've ohmed out all of the coils that I wound and installed and found no issues there. I've also inspected the factory-installed surface mount chips for solder bridges and nothing found.? Is there something else I should check before assuming that I was sent a defective unit?? Has anyone here had these same problems?? Were you able to diagnose and fix it and how???
Thanks, Jerry AC5JM??
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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 2.2uF cap in position C510, I do not know. In any event, worry about getting the proper capacitor into position C509 first! Hopefully Hans will see your discovery and have some informative words.
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QMX Power supply board question
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 right next to it? Mine is and i cant see any solder bridge.? The longer i look at the wiring diagram the less sure i become.
Mike G0HIO
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Re: I completed the assembly of the new QMX
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!
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Re: I completed the assembly of the new QMX
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 on both edges there's just enough room.
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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 = 2.2 μf... right? Please, have I got that right? I am still from the vacuum tube era of micro farads and micro-micro farads or "mickey-mike!" This μ, pico and nano have me snowed! Micro I got solid. The p and n not so much. Yeah, and we even got FARADS today!
So anyway, looks like either a parts change or the parts stuffer went nuts.... I'll just hold my breath until Hans chimes in!
73
Karl
KI4ZUQ
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Re: I completed the assembly of the new QMX
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 will fix this short.
I have exactly this same problem to fix, when I get to
this board in the assembly process!
Good Luck!
Paul -- AI7JR
On 8/18/23 07:44, GIUSEPPE wrote:
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the red dots give me a short while the blue dots
are ok, I don't know what to do.
Giuseppe iu8eun
I tested at this moment with the DVM in the
points marked in blue on the photo and it doesn't bring any
short circuit.? Should I check somewhere else that there
isn't a short before powering the QMX????? Thank you
Giuseppe iu8eun
There is no short circuit on these two
points.? I already tried it last night.
Giuseppe iu8eun
Hello Giuseppe
If you have the?short between the Q103? and
Q104 drains you have to resolve this BEFORE
applying power.?
FYI I have now added this to the assembly
manual, I uploaded the edited version this
morning.?
On Fri, Aug 18,
2023 at 11:28?AM GIUSEPPE < iw8rsb@...>
wrote:
Hello Hans and everyone, last
night I checked with the DVM tester the two
points you marked on the board and it reported a
short circuit, then I unplugged the board to be
sure and the short was still present, all the
soldering points they are perfect and clean even
on the main board.? Do you think it would be
appropriate to try to make the first start to
load the firmware ???? You can look for the
problem elsewhere in the tab.? Thank you .
Giuseppe iu8eun
Hi Dav, thank you.? Having
already assembled 2 QCX MINI and 2 U3S
including 1 multiband and 3 QLG I had no
difficulty building it, you just need a lot
of patience, a steady hand and an eagle
eye.? The space is very limited and there is
the risk of burning some nearby smds.? I'll
see what I can do tonight.? Thanks to Hans
who keeps us active with these magical
little radio boxes to build with which you
can work wonders in long distance qso.? Have
a nice day.
Giuseppe iu8eun
Hi Giuseppe,
Well done on building
the QMX.
You will need to install
the firmware before using the radio,
in accordance with the instructions in
the assembly manual. It's nothing to
fear; basically just drag-and-drop the
firmware file.
Good luck!
73,
Dav M0WDV
On
Thu, 17 Aug 2023, 08:28 GIUSEPPE,
< iw8rsb@...>
wrote:
Hello Hans and all
the team, I completed the
assembly of the new QMX
yesterday evening, today I will
do the first ignition I hope
everything goes well, I wanted
to ask you if it is really
necessary to install the new
firmware as described in the
manual or the QMX can work
without update.? Hope it works
the first time you turn it on.?
Thank you and good day.
Giuseppe iu8eun
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It looks like C509 is a crucial pathway for RX_In
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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 SUPPOSED to be a 2.2μ according to the parts list. C509 s'posed to be a .1μ ... C509 was there at one time but appears to have bee on edge with a solder bridge. Broke out the solder bridge. This might have something to do withe the receiver being deaf....
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FS: QCX "Classic" 40 meters
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. Has the QRP Labs AGC board installed. I added a power on/off switch on the right side. Radio is clean and working. Power output is 3 Watts into a dummy load with 13.8 VDC input. Comes with fused DC power cord. Manual may be downloaded from QRP Labs' web site.
Price is $100 postpaid USA. Payment via PayPal or USPS Money Order. No trades, please.
Shipment will be via US Mail. I ship on Thursdays only. I pack everything carefully to avoid shipping damage.
?
73/72,
Dean K5DH
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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 mine set to VFO B and performed RF Sweeps and got crummy graphs like yours. Switched to VFO A, and back to my beautiful graphs. Hopefully this is the fix for you!
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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. Squeezing the turns on L513 made a significant difference. I also added one turn to L525 and that helped a bunch. It got me up to 4.4 watts.?
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On Aug 18, 2023, at 13:43, Rick NF6G < rdante@...> wrote:
Karl, there is one more fix for you to make. Refer to?
the section Low 20m output power on early QMX builds
Capacitors C525 and C516 values incorrectly swapped in the 1.00e build manual. These are the two capacitors next to the PTT port. I don't know that these will have any affect on your RF sweep graphs, but if you haven't already performed the swap, power output will be low, as stated in the troubleshooting guide.
?
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Karl, there is one more fix for you to make. Refer to?
the section Low 20m output power on early QMX builds
Capacitors C525 and C516 values incorrectly swapped in the 1.00e build manual. These are the two capacitors next to the PTT port. I don't know that these will have any affect on your RF sweep graphs, but if you haven't already performed the swap, power output will be low, as stated in the troubleshooting guide.
?
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Re: QMX Failure Discovered...and new problem
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 capacitors, it could go substantially higher in Receive and then trigger a latchup melt-down of the chip. The energy to produce this failure may have come from the 5 Volt supply. You seem to doubt that, and that is legit. It also might have come in from the clock generator, but that seems to be working, as you can transmit power. The remaining possibility is that the transmitter itself has fried that chip, and probably the mux chip ahead of it , too, or that a latch up as described above has happened. These scenarios seem unlikely but cannot be discarded. JZ KJ4A On Fri, Aug 18, 2023 at 5:01?AM Daniel Walter via groups.io <nm3a@...> wrote:
Kees,
Yes, I am sure there is no short between Q103/Q104. Tested 5 V line prior to installing the p/s and after and checked on self test via USB. 5 V line never any higher than 5 V.
--
73, Dan NM3A
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Re: Fldigi and QMX successful???
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 any mode with fldigi.
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On Aug 18, 2023, at 11:07, Peter OM4AEI < om4aei@...> wrote:
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Re: QMX Poor contrast with backlight on
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 little bit yielded enough clearance to put things right! Next time I remove the entire unit from the case, I'll flatten the solder hill on pin#3 and/or put a bit of kapton tape between L101 and pin#3. Unfortunately, I misplaced my kapton tape a couple weeks before my QMX build, but until then all seems good.
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Re: #qdx Middle band QDX 30m - 15m
#qdx
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 second harmonic did not meet FCC requirements on 30m.? I have been toying with changing out the filter, but wasn't sure it was worth the effort.
.Andy W3SW
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Re: Fldigi and QMX successful???
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Re: QMX Failure Discovered...and new problem
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
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Re: Fldigi and QMX successful???
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
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Karl
Paul - AI7JR