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QMX+ JUST WON'T WORK
开云体育Dear Members, I just can't get past the diagnostics page. I think my SMP BOARDS are not coming on due to troubles on my PC board.? Radio draws 210 ma with an 8.1V supply voltage.?? When I first started out the current was higher but found a short on the GPS antenna connector that was shorting the 3.3v bus.? all the switching seems to work but I have no backlight to the front panel and a line of some kind of digital thing that uses all the signal lines on the top of the readout.? I have put my fingers on every electronic part and there is no heat except for the small 3.3v SMP CARD.? (It isn't real hot but it is warm).? Here is the screenshot of my hardware diagnostics Page: Here is the view of the back of the main board.? I have gone over
this with the loup until I am almost blind. top of main board: here is the front panel: I do see the broken mike jack on front panel.?? I will have to
get another one of them.? Any suggestions gratefully accepted.? 73 Dave WA5DJJ
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73 Dave WA5DJJ SUPER QRSS/WSPR (160m to 6m) GRABBER WEBSITE: |
开云体育Hi David ? ? ? ? ? ? ?I had exactly the same problem with a QMX+,ordered a new set of power modules,low voltage now 3.4v current 80ma,device now working. ? ?Best of luck ? ? ? ? ? ? ?Regards ? ? ? ? ? ? ? ? ? Mike G6GN On 16 Aug 2024, at 18:59, David R. Hassall WA5DJJ <dhassall@...> wrote:
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开云体育Looks to me like the 5V SMPS is up, which implies the MPU is running. Something's up on the 3.3V supply, though. -- Paul -- AI7JR |
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On Fri, Aug 16, 2024 at 07:59 PM, David R. Hassall WA5DJJ wrote:
Current meter shows 210 ma when turned onDave, this looks ok. Please check VDD by an DMM, There is a pin at the mainboard. Duty cycle = Duty max looks like a overload at VDD but 210 mA looks not like overload.
So we have to check if the controller is reading VDD the correct way.
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73, Ludwig |
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On Fri, Aug 16, 2024 at 10:34 PM, @Ludwig_DH8WN wrote:
Dave, this looks ok. Please check VDD by an DMM, There is a pin at the mainboard.Dave, sorry I made a mistake. In the current situation VDD for the mainboard is produced by the linear regulator and should be around 3.0 V (see VDD pin on mainboard).
VDD from the SMPS exists only on Plug-in PCB#2 (the one with the 6 pin header) and isn't connected to VDD on the mainboard. The voltage shown in Diagnostics comes from the SMPS and we should check this voltage. The tantal capacitor is a good place to check. But please take care not to connect other points using your probe.
The value shown in Diagnostics is calculated from the signal ADC_3V3. This should have SMPS-VDD * 0.5.
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73 Ludwig |
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Dave, you may check Plug-in PCB#2 offline using QMX QMX_Plus Power supply test Process from the QRP Labs Wiki.
At the end of the text you find the methode to check the proper function of the zener diode. Do this only if the current is limited to 50 mA or a bit less.
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73 Ludwig |
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On Sat, Aug 17, 2024 at 04:05 AM, @Ludwig_DH8WN wrote:
Dear Ludwig, thanks for the hints.?? I will work my way through them and let you know what I find.? Sorry I have been gone for a few days and wasn't able to answer earlier.?? Thanks to the others that gave me hints.?? I did buy a new set of SMPS POWER SUPPLY modules but I think I have also broke them in the process.? When I was building the QMX+ a little black part fell out one day when I was working on it and I have not found out if it was really out of my QCX+ or something that stuck to My PC board and fell out when I was working one it.? I have checked all the surface mount areas on the board carefully and find nothing on the board that is missing.?? I did have the front panel on it? and it is very difficult to check the parts under the LED READOUT.? But on the pictorial sheet there are no diodes (little black parts) on there but the readout doesn't come on either and makes me very suspicious that something under there is missing.? But the resistors are a different shape and size to the part that just fell out on? the bench top while I was trying to get this thing to work.?? Of course, there are no numbers or identifying marks on the part that fell out except a dot.? But I hope to get back to working on it and try to ohm out all the traces to make sure that they are connected.?? My short may be on there also...But I did bend the tang of the redout as outlined in the manual and looking under the board it appears? to clear any of the circuit components that are underneath.?? But time will only tell.?? I bought another QCX+ to build if I can't get this one running. I want it for a 6M receiver on my QRSS Grabber.
Take care and have fun.
73 Dave WA5DJJ ?
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Yes it is hard to put the nuts on the SMPS mounting screws - if you turn the nuts to tighten them. I still take a page from Hans' original suggestion to ream out the threads on the nuts that are used as spacers. Then you can just hold the fastening nuts on the top and screw the mounting screws down tight. That way you don't disturb the close parts on top of the board.?
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73, Dan? NM3A |
Paul - AI7JR