Re: QMX+ No transmit or receive
:-)
On 12/30/24 21:15, Joel Macneill via
groups.io wrote:
Okay Paul. Thanks. Just my interpretation of the
schematic. I will take that under advisement when I check it
again .
--
Paul -- AI7JR
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Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#ABS
#ATU
#PSU
#QMXplus
To all who are asking about being part of a new group buy of the ABS add-on for the QMX+:
Cal and I have you on our list for a potential new group buy of the ABS boards and components. Sorry for the delay in responses.
We are still busy getting the current group buy out to the 30+ who subscribed to the initial buy, and resolving some (hopefully minor) issues we have found in further testing. When we have completed that, we will look at logistics, etc., and make a decision about another group buy for those who missed the first one. The prices for a second group buy, if we decide to continue with it (which is likely), will depend on the number who subscribe to it, since the cost depends on quantity discounts. Please be patient with us as we get the first buy completed.
Here are the ones we have on the list so far who have requested to be part of a second group buy:
ZL1ANY Stephen
W9LG Michael
KF7EJ Will
K7RAN Randy
KS4NS Dale
OZ1ES Erik
Nico Smith
Dave Campbell
Thank you,
Stan KC7XE
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Re: QMX+ No transmit or receive
Okay Paul. Thanks. Just my interpretation of the schematic. I will take that under advisement when I check it again .
If Q508 is turned on by the gate voltage, I'd expect 0 volts on
the drain. This FET is really operating as a switch... Source
connects to DC ground through L503 and to the receiver input,
signal from C509 connects to the antenna through all the filters.
I think you're seeing what you should, for receive mode.
73, Paul -- AI7JR
On 12/30/24 20:33, Joel Macneill via
groups.io wrote:
So I had some more time this evening to do some
quick checks. First off, it requires a look at transmit and
receive schematics to get a good grasp of the receive path but
since I have continuity across the LPF stage, i thought i
would check out Q508. I am still connected to the dummy load
so I know it is difficult to turn the FET on, but I thought I
would get some idle voltages .These are my findings....Q508
drain is connected to C509 but also connected to a 12v supply
which is offering only 0v to the drain, although the schematic
says there should be 12v at the drain (reduced of course thru
the 470k resistor). If i have this correct, the source should
be receive signal in and the gate modulated by receive as
well. I am showing 12v at one side of R510 but none at the
other. I shouldn't really see 0v at the other side of the
resistor unless it is attached to ground and i am not ready to
say yet that it is an open resistor because of the necessity
of lifting it and removing from circuit. Don't want to do that
with SMD resistors. Lol. I have included two pictures of me
testing r510.
--
Paul -- AI7JR
|
Re: QMX+ No transmit or receive
If Q508 is turned on by the gate voltage, I'd expect 0 volts on
the drain. This FET is really operating as a switch... Source
connects to DC ground through L503 and to the receiver input,
signal from C509 connects to the antenna through all the filters.
I think you're seeing what you should, for receive mode.
73, Paul -- AI7JR
On 12/30/24 20:33, Joel Macneill via
groups.io wrote:
So I had some more time this evening to do some
quick checks. First off, it requires a look at transmit and
receive schematics to get a good grasp of the receive path but
since I have continuity across the LPF stage, i thought i
would check out Q508. I am still connected to the dummy load
so I know it is difficult to turn the FET on, but I thought I
would get some idle voltages .These are my findings....Q508
drain is connected to C509 but also connected to a 12v supply
which is offering only 0v to the drain, although the schematic
says there should be 12v at the drain (reduced of course thru
the 470k resistor). If i have this correct, the source should
be receive signal in and the gate modulated by receive as
well. I am showing 12v at one side of R510 but none at the
other. I shouldn't really see 0v at the other side of the
resistor unless it is attached to ground and i am not ready to
say yet that it is an open resistor because of the necessity
of lifting it and removing from circuit. Don't want to do that
with SMD resistors. Lol. I have included two pictures of me
testing r510.
--
Paul -- AI7JR
|
Please see this thread from a couple of weeks ago, a user with the same question:
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Re: QMX+ No transmit or receive
So I had some more time this evening to do some quick checks. First off, it requires a look at transmit and receive schematics to get a good grasp of the receive path but since I have continuity across the LPF stage, i thought i would check out Q508. I am still connected to the dummy load so I know it is difficult to turn the FET on, but I thought I would get some idle voltages .These are my findings....Q508 drain is connected to C509 but also connected to a 12v supply which is offering only 0v to the drain, although the schematic says there should be 12v at the drain (reduced of course thru the 470k resistor). If i have this correct, the source should be receive signal in and the gate modulated by receive as well. I am showing 12v at one side of R510 but none at the other. I shouldn't really see 0v at the other side of the resistor unless it is attached to ground and i am not ready to say yet that it is an open resistor because of the necessity of lifting it and removing from circuit. Don't want to do that with SMD resistors. Lol. I have included two pictures of me testing r510.
Very true Ludwig. Thanks for the link. Sweeps are still definitely not my strong point but one things for sure, after checking the board several times, I still found a solder flake. Thanks very much and I will report any further findings.
Joel, some HAM are radio experts and some more are on the way to this state. Your doing was meaningful. I guess, now you know your QMX better than before and has gained new experience, one more step to the expert.
If the TX path is ok the problem for RX should be located in the part from Q508 up to IC407.
Your former rf sweep showed a very low level. Maybe this is caused by a bad connection (L401, T401) or by a broken element (IC40x). A good way to check this is the last method described in QMX QMX_plus Audio PCM1804. But you need a signal generator and an (cheap) oscilloscope. Using this method you may decide the problem is either in the part up to the OP amps or in the PCM1804. But first you may check the relevant parts visual (remember the "almost un-recognizeable flake of solder.").
73 Ludwig
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Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#ABS
#ATU
#PSU
#QMXplus
Hi
If possible I would also like to sign up to a group buy if available
Thanks
de stephen zl1any
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Hi Mike,
I'm expecting my assembled QMX very soon. I received an iPad mini 6th generation as gift. It has OS version 17.4.1. What cabling will I need to connect them together to operate iFTx? I'm normally not a Mac user, but the iPad was a gift and I'd like to operate FT8 for POTA use.
Thanks,
Tom, N8EUI
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Good luck in finding the failed part - the ICs are more likely than any of the other parts, and there are only a few of them on Vcc, so it shouldn't take too long.
And if you go with the linear power supply route - a couple of others have done that, too - so look at the messages in this forum for some important info, such as a resistor that needs to be in place to keep the firmware happy with the power supply status. There was a recent thread this past month with some details. Myself, I like the current design - it is efficient and gives a significantly increased battery life compared to using a linear supply. And I need my radio/battery package to be as small/light as possible and give plenty of runtime.
Stan KC7XE.
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Re: 2m/440 cw/ssb qrplabs kit?
Spurious regulations are tougher in this spectrum because it's used for public safety. Perhaps a tiny SA may not be good enough. So filters might have to be factory aligned. Perhaps better to assemble entire vhf uhf rig at the factory.
A 144 MHz transceiver that could also receive 432 MHz might be interesting.
But the entrepreneur gets to decide what is viable.
Curt
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Re: QMX no transmit on 60M, large B on display between freq and mode
What was happening is that I had split "fake" enabled and the Region 2 band limits. When the rig split on 60M it was outside the channel and TX shut as it does for high SWR. I changed the band limit to "none" and all is good now.
73, Bill NZ0T
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Stan Dye via groups.io <standye@...> wrote: If your receive is working properly, it's probably not a component on
the main board - most of the receive section components are on Vcc.
Does receive still work? Hard to tell. There's normal noise, so it probably works at least partially, but I don't want to stress the board more... I would measure the main-board resistance between the 5V rail and gnd,
without the power supply in place. This should have several Kohms of
resistance, if not, there is a failure somewhere on the main board.
Hopefully it is OK and the only failure is in the 5V supply. 23 ohms, measured on the main board with power supply boards removed. No wonder the inductor is getting bloody hot. I isolated it by lifting the Vcc pins of the ICs one at a time until the
short disappeared. But this IC being damaged also destroyed all signal
receive functionality. I think this is what I'll do -- make a list of possible components and just disconnect them one at a time, measuring the resistance. An option to consider is to order a set of the little power supply
boards from qrp-labs (on their spare parts page) - they are very
inexpensive, and may save you some troubleshooting and repair. When (if) I fix the issue with the short on the main board and verify that everything works, I'll think about it -- right now I have a linear regulator instead of a 3V3 buck one, which seems to work just fine. Another option I considered is designing a custom board with just a power switch and two linear regulators instead of these two boards. I don't like the idea that the control loop goes via the CPU. Of all design decisions in the QMX, and despite the trick with adjusting the switching frequency so the harmonics don't interfere with reception, I'm not a big fan of this solution. Thanks!
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Re: Updated QMX Condensed Menu plus Excerpts from the QMX Operating Manual with Comments
Derek, I may be confused but I am unable to find any document(s) or other file(s) attached.
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QMX(+) Build experience, Poor Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test and resolution with new PCM1804
Good evening! Big thank you to Hans and everyone else in this forum! I had a lot of fun building these kits and I couldn’t have successfully completed them without the folks who ask and answer questions here. I wanted to make this post to thank everyone but also to detail some of the problems I encountered, the equipment I used, and also how I resolved them.
This is a long post for anyone who’s interested but TLDR: I built 2 QMX+s and 1 QMX and all three needed new PCM1804s.
I purchased a QMX+ in May and a couple weeks later got to work. I had built a couple other kits and antennas previously but this was the most involved so far. I was able to make it through the build and load firmware but I couldn’t run all of the self-tests and the audio was loud static. I didn’t have enough experience or equipment to troubleshoot myself but luckily Jeff Moor W1NC reached out and offered to help. See https://groups.io/g/QRPLabs/message/126274 for my original post. I mailed him my QMX+ and he got it back to me in about a week with several fixes. It had several bad joints, insufficiently scraped enamel, a bad PCM1804, and a bad inductor. Thanks Jeff for your knowledge, experience, and willingness to help the community with your excellent service! I’m extremely pleased with the outcome and my QMX+.
I used:
I primarily used the conical soldering iron tip with success but in retrospect, I should have primarily used the wedge tip. The head magnifier with 3x magnification, plenty of light, solder wick, flux, and desoldering tool were critical. The loupe was ok but the head magnifier would have been enough. I ruined the side-cutters on solder wick.
Pleased but not content apparently because in July, I purchased another QMX+ so that I could use the lessons learned from the first unit and hopefully successfully build another myself. The kit stayed in the box until my wife & kids went on vacation for about a week. Over a couple of evenings, I had a great time building the kit, using all my new knowledge and experience, but when running the terminal tests, I had bad results on Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test. I reworked some of my joints but to no avail. Some example scans, before and after 1804 replacement, are attached.
With bad PCM1804
   
I started diving into groups.io posts and determined that maybe I should invest in more test equipment and that I might have a bad PCM1804 chip. I ordered two more PCM1804 chips (just in case I ruined one). I also ordered a QMX because I was more confident in my kit building skills. In the mean time, I also purchased an LCR meter, a TinySA Ultra (for its signal generator), and an oscilloscope. Probably overkill but I had my eye on them for a while.
Over the winter holiday break, I built the QMX. I enjoyed and had more confidence in my build but I had very similar problems to my 2nd QMX+ build during self-tests. During this build, I used a grounding strap/bracelet the entire time so I was pretty sure it wasn’t static discharge related. What are the odds I’d have the same problem twice? I found this post https://groups.io/g/QRPLabs/topic/109639794#msg133769, indicating the PCM1804. I did the diagnostic tests from https://groups.io/g/QRPLabs/wiki/37111 and determined that replacing the PCM1804 was my next step. Luckily I had two new PCM1804’s in stock although I previously intended on only needing one.
After doing research here and on youtube for replacing SMDs, I got a ChipQuik kit and a hot air rework station. After doing some tests, I decided I would just use the ChipQuik, which is basically easy-mode for low-skill chip removal. My process was basically, remove the chip using flux and ChipQuick, clean the left-over ChipQuik with fluxed solder wick, clean the board with 99% IPA, flux the new chip legs, place the chip carefully on the board (head magnification essential), put a small amount of solder on the iron tip, tack the first pin, ensure chip alignment, then use the solder drag technique to solder the remaining legs. It doesn’t take much solder and I removed any excess with fluxed wick. I went back over the pins to ensure uniform connections and triple-checked for bridges. I repeated the process for the QMX+.
After replacing the chips, the terminal hardware tests all returned good results on both the QMX and QMX+. For good measure, I compared them with results from the QMX+ that Jeff Moore repaired for me and they were comparable. Once again, I’m super appreciative of all the folks here asking questions and giving helpful information. I’ve learned quite a bit about reading schematics, the function of different parts/sections of these radios, and test procedures. Thanks for everything!
With new PCM1804:
   
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Re: Updated QMX Condensed Menu plus Excerpts from the QMX Operating Manual with Comments
I want to thank the ones who contributed to this document from here on groups.io/g/QRPLabs or QRP Labs QMX enthusiasts. Whether be formating, corrections, or motivation to research more. I feel I am a good stopping point for now.
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
On Mon, Dec 30, 2024 at 01:47 PM, Adam wrote:
L101 (the one on the 5V board) gets very hot
No this is not normal. It gets only warm during normal operations, including transmit.
Note: it is dangerous to operate the QMX without D108, especially if there is a short on the output of the 5V supply somewhere. This is because the CPU tries in vain to raise the voltage to 5V, increasing the output of the switching supply, which (without D108) puts 12V on the 5V VCC rail, significantly increasing the current being sourced into the short - that is likely why your L101 is getting hot. The added current may burn through whatever is shorting, and suddenly put 12V on all the 5V parts.
So something must be partially shorted/failed on the 5V board, or on the 5V components on the main board to cause this. If your receive is working properly, it's probably not a component on the main board - most of the receive section components are on Vcc. Does receive still work? On one of my units, I inadvertently shorted 12V to Vcc, and in additions to causing failures on the 5V power supply, it damaged IC403 to have an internal near short to ground. I isolated it by lifting the Vcc pins of the ICs one at a time until the short disappeared. But this IC being damaged also destroyed all signal receive functionality.
I would measure the main-board resistance between the 5V rail and gnd, without the power supply in place. This should have several Kohms of resistance, if not, there is a failure somewhere on the main board. Hopefully it is OK and the only failure is in the 5V supply.
An option to consider is to order a set of the little power supply boards from qrp-labs (on their spare parts page) - they are very inexpensive, and may save you some troubleshooting and repair.
Stan KC7XE
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Re: Full Band Coverage QMX+
Everything is working perfectly now, thanks for all the help.
--
Trevor (N0YMA)
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Re: QMX no transmit on 60M, large B on display between freq and mode
Thanks John, that was it!
73, Bill NZ0T
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Re: QMX no transmit on 60M, large B on display between freq and mode
Bill,
This could be the 'out of band' indication - see p10 of the Operating Manual 1-00-026.
73 John M0JBA
I working 60M FTB last night and my QMX was humming along just fine. Then it stopped transmitting and a capital B appeared between the frequency and mode on the display. RX still works fine but the QMX will not transmit in CW or digital but just on 60M - no other band is affected. I did look through the operating manual but did not find anything.
73, Bill NZ0T
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Adam via groups.io <qrp-labs@...> wrote: Sadly, it's not a diode (nothing changed when I removed it). An update. The diode (D109) was in fact damaged, but not only the diode. Something else on the 3V3 board was wrong as well. When trying to diagnose it, a capacitor on the board blew up (I'm almost sure I wired everything correctly... turns out I didn't), and as I first wanted to quickly test if the radio works, I made a linear regulator, provided artificial ADC_3V3 signal just to satisfy the CPU, and it works. That's great. Another issue is that L101 (the one on the 5V board) gets very hot (it got to 110°C before I stopped the test). D108 (protection diode on the 5V board) was damaged as well, but when I removed it, nothing changed. Radio works, L101 gets insanely hot, and I'm afraid of running it for too long (longer than ~20 seconds it takes L101 to reach this temperature). Any ideas on what else could I check? Or maybe this temperature is normal (I highly doubt)?
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Paul - AI7JR
Paul K7VIQ
UPNORTHOF48 :