GM everyone,
I was able to complete the kit and make confirmed QSOs on most bands and modes.
At one point, the unit seemed to be unable to switch on at all. Nothing on the display. I checked the battery, power cable, 12V socket, there is voltage in V-IN everywhere, even at the switch-on button. There does not seem to be any short between ground nor V-IN, Vcc nor Vdd.

The only thing i can see is that i had overcharged my battery to 13V or so. I would think that this could affect the PA but probably not the display or CPU.
What would you suggest i check, do i need another display or unit ?
Many thanks,
Sly Coulombe VA2YZX

Sly, If it is a Rev.1 you may have popped D106 or D109. Also, did you completely disconnect the power from the radio, wait a little while, then reconnect?? Something like this happened to me and just doing that brought it back to life.

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73, Dan - W2DLC

GM Daniel, thanks for your reply.

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For D106 i get a 1.478V forward, 0.224V reverse.

For D109 i get a 0.124V forward (DMM red left side), 0.374V reverse.

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i did disconnect-reconnect a bunch of times, to no avail.

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Sly VA2YZX

Those diode measurements probably look ok - they will depend on how your particular meter energizes the diode.

You didn't mention checking the 12V bus (Vin and 12V are different, separated by a switch).? All three (12V, Vcc and Vdd) should show several kOhms resistance to ground, and also should show MOhms between each other and Vin.

After checking those, also check the current draw while you are pressing the power-on button.? If it is drawing 80-100mA or so, the processor may be starting up (but not getting the power supplies turned on), and you may be able to check the diagnostics page via a terminal connection (while holding down the button).

Stan

Thanks Stan, i'll check and get back to you...

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I read somewhere else than some had issues with the 12V connector. (not being the proper size ??)? I did also, as sometimes if i moved the unit the connector would move a bit and power switched off.? I would reinsert the 12V connector and it would power on again.? I heard somewhere that this could cause multiple on-offs and blow a diode somewhere.

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Maybe this info will help in troubleshooting, but now, no matter how i insert the 12V plug, nothing happens.

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On Mon, Nov 25, 2024 at 01:57 PM, Sly Coulombe - VA2YZX wrote:

some had issues with the 12V connector. (not being the proper size ??)

Yes, this can be a problem, because while you think the 12V is a steady connection, it can be having many very short disconnects, dozens of them each time the QMX or cable is moved, which eventually may cause a problem.? A couple of people had this result in a blown D109, and in early hardware revisions, also D106.? But if yours was blown, it would probably measure 0V both directions, because they typically fail shorted, disabling the QMX (if they fail open, the QMX would continue to operate).? So your issue may be something else.

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You need to make sure that the DC plug you use is a 5.5/2.1mm plug (that is 2.1mm inner hole diameter).? Another popular size is 5.1/2.5mm, which has too large a hole to properly connect - unfortunately, it does appear to get a good connection most of the time.? It is cheap and easy to replace the connector on the end of your cable with the correct one, much easier than debugging a dead QMX....

Stan

On Mon, Nov 25, 2024 at 02:09 PM, Stan Dye wrote:

You need to make sure that the DC plug you use is a 5.5/2.1mm plug (that is 2.1mm inner hole diameter).? Another popular size is 5.1/2.5mm, which has too large a hole to properly connect

What I do is use the shank of a 2.5mm drill.? If it will fit then it's a 2.5mm plug and NOT suitable for a QMX. If it doesn't it should be OK.? Don't trust what you order, some suppliers will send the wrong one.

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Chris

Thanks everyone,

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i just ordered some 2.1mm as all the ones i have here looked the same, i tested them inserting a DMM probe for size.? I dont know the size but they are all the same.

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I tried to see if i had an amperage reading as i powered on.? The reading moved up to like 0.1 mA, then back to zero.

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All hell broke loose when i switched battery, using another DC connector so the connector size theory makes sense.

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Would anyone know what other diode to test ??

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Sly VA2YZX

UPDATE:? i received my 2.1 mm connectors.? I know they are smaller as my DMM probe does not go inside it as it does for what was probably a 2.5 mm.

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I checked for voltage, and there is voltage in a bunch of places.? No reading at Vcc nor Vdd.? The diodes i checked seemed ok, but there is something weird:

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I check for voltage at Q105 and Q103.

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I do get 13V on one pin, and about 12.5V on the other.? However, on the back tab of 105 i don't get a reading, but i DO get 13V on the back tab of Q103.

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Please advise,

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Sly VA2YZX

You should read /g/QRPLabs/wiki/36878

on this group's wiki, along with a few of the other topics about the power supplies.

But for a direct answer, the Q105 tab will only show voltage when the power-on button is pushed, and then IF the processor gets started up, it will start up the power supplies and assert PWR_HOLD, which will then keep that Q105 switched on.? Otherwise the voltage will disappear when you release the power-on button.

Read up on the related items in the wiki, and they will lead you through some things to check.

Stan KC7XE

TU Stan for the reference.

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Sly VA2YZX

2nd UPDATE:

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i checked the voltage upon powering up with the switch on IC101 which should provide 3.3V under normal circumstances as i understand the process.? The max i get at the input of IC101 after switch on is 500mV, then trickle down to 0.? At the output, about 300mV then zero.

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Q101:? in diode mode (DMM) i get:?

D-G+ = OL ???????????? G-D+ = 2.97V

D-S+ =? 0.626 V???? D+S- = 2.92V

S-G+ =? OL????????????? S+G- = 0.626V

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Q102

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Those transistors may be ok.

What I would measure is the following voltages while the power button is pressed, all referenced to ground:

1) drain of Q105 (should be same as source of Q102)

2) gate of Q101 (should be pulled up to similar voltage as above)

3) drain of Q101 (should be getting switched on, going down to near 0V)

4) source of Q101 (should be 0V unless board soldering problem)

You already did the drain of Q102 (at input of IC101), but it's not what it should be, so one of the above voltages must be wrong, either due to a broken transistor or broken connection.

GM Stan, here are my results:

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1) drain of Q105 (should be same as source of Q102)? = peaks to 5-6V upon start button, then back down to 0

??????????????????????????? Q102 source:? 5-6V upon startup then 0

2) gate of Q101 (should be pulled up to similar voltage as above) =? 2.5V upon startup, then 0

3) drain of Q101 (should be getting switched on, going down to near 0V)? =? up to 0.5V, then back to 0

4) source of Q101 (should be 0V unless board soldering problem)??? =? 0V all the time

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PowerOn is always ON at 13V on the + side of D101

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Vdd and Vcc go up to about 5mV then 0 again on powerup

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BTU, Sly VA2YZX

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Ok, Sly.? You have a good mystery here.

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One question about your measurements: You state that you see a voltage, then "back down to 0".? And in your preceeding 'update 2' measurement, you said the input of IC101 "trickled down to 0".? Do these changes down to 0 happen when you release the power-on button, or do they transition while you are holding the button?? (for the rest of this response, I will assume it is after you release the button)

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One question about your hardware:? Is it QMX+ v2 with the smps power supplies integrated onto the board, or v1 with the two little smps boards?

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There are two very different possibilities I see:

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1) Something is pulling down on your 12V bus, such that when you press the power-on button, which turns on the 12v bus (the tab of Q105), it never gets enough voltage up to turn on IC101 via Q102.? So the processor never turns on and your 12v power bus goes down to zero. (Q102/Q101 seems to be turning on properly, otherwise you would never see a voltage at the input of IC101).

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2) Your power-on is successfully turning on the 3.3V power to the processor, which engages the 5V Vcc and 3V Vdd switched supplies (which would explain why you momentarily see a non-zero reading on Vcc).? But one or both of them has a fault, which causes the 3.3V to get shorted down, which turns everything back off.? Just measuring with a DMM you probably would not see this, because the input to IC101 (and its output) would only be on for about 1/4 second, which is all the time it takes the processor to turn on the other supplies and disable the IC101 by pulling LIN_REG_EN low.

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If #1 is true, there are several places where a solder-whisker or solder-bridged pins could cause the 12V to get shorted down.? Or it is less likely, but it could be a faulty capacitor like C104 or C105, which partially short to ground.? Since you do see some voltage on 12V (Q105 tab), it is not a direct short, but something getting pulled down hard such that the voltage can't get up above 5-6V.? Measure the resistance between the 12V +V point and ground - it should be at least at least 20Kohms.? If you have the small smps cards, and the measurement is much lower, try measuring with one of the cards removed, then the other.? Inspect both sides of the cards very carefully under high magnification for any bridged connections or solder remnants.? Also measure the current draw while the power button is pushed, and see if it changes.

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If #2 is true, I would make a guess, partially based on your use of the 5.5/2.5mm connector and other reports here, that your D109 has faulted, and is pulling down the 3.3V shortly after it comes up, causing everything to go off again.? If so, you should see some current draw while you have the button pushed.? I think the only way you could verify this hypothesis is to lift one end of the D109 (or remove it), and see if the problem goes away.? If D109 is the fault, the radio should work properly without it, but you do want to replace D109 because it prevents other serious damage if there is an over-voltage fault.

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If the current draw while the button is still pressed quickly goes to zero (or very small), I don't yet know what could cause that...

I hope something here is helpful...

Stan KC7XE

Stan, VMT for your help.

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My board is ver.2.

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It would make sense that D109 would be unserviceable, as many had that snag as well after using a 2.5mm connector.? I can try to lift D109 on one side, but my abilities to handle surface mount is quite limited.? I could solder a dab on the pads and replace the SMT mounting a thru-hole component, which is easier for me to handle.? Could you suggest a replacement part number ?

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I get proper reading from my DMM on D109 in diode mode, but the resistance between ground and the + side of D109 is about 220ohms.? That looks suspicious.

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Thanks again,

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Sly VA2YZX

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If you want to try and replace it with a leaded part, this one should do

or any 3.6V 500mW zener.? Don't get higher wattage or a different voltage, the characteristics change too much.

Stan KC7XE

GM Stan,

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i lifted D109 and no change.? I re-soldered successfully using part of a discarded lead, and DMM tests are as prior.

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The most i get from Vcc and Vdd (at JP105) is 5-10mV, which holds as i hold the power on button.

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Could a major IC be fried at this point ?

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Sly VA2YZX

Well, I guess it is good that D109 is really working.? That removes one more variable

I wouldn't jump to the conclusion that it's one of the major ICs yet (because I'm stubborn: it could be one of them, but they are normally less likely to fail, so I usually try everything else first).

But I also don't know what else I can have you try that only requires a DMM, and not difficult part removal.

Do you have a way to measure the current that is being drawn, before and while you press the 'on' button?? It would be interesting to know, but may not lead directly to the problem.? My next step would be to use an oscilloscope to look at some signals to ascertain which of my #1 or #2 hypothesis (of the previous post) is correct, if either, and then, based on that answer, to selectively start lifting parts legs to find what will change the behavior.?

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Other than that, I am out of ideas for right now.? Maybe someone else can think of something.?

Stan KC7XE