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I was listening to some CW on 10 meters and accidentally pulled the headphones plug out of the jack a little. Upon pushing it back in, the QMX died and now won't turn back on. What could have caused that?

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73, Dan - W2DLC

I looked at those, and they are both in there pretty solidly. I wonder if there might have been a momentary voltage spike that took out the Zener diode.? I'll put a meter on it later today.

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73, Dan - W2DLC

Yep? Troubleshoot lack of power on should take you to whats gone wrong.? When you know try and figure out how you might be able to make that happen mechanically? . .?

Hi Dan,

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A similar thing happened to me.

You can read about it here: ?/g/QRPLabs/topic/107459127

Did you add the optional insulating tape on the encoder?

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73, Mike KK7ER

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Yes, I put the insulating tape on the encoder. It's still intact.?

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73, Dan - W2DLC

The tape on the encoder was the first thing I looked at, but it's possible that a short occurred somewhere else as a result of the vibration of pushing the headphones in. I'll have to take a really close look at things and check the power rails with a meter when I can get to it.. I did notice that I hear a thump, thump when I pushed the left encoder button to try to turn it back on. That makes me think that the switching transistor is still OK.?

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73, Dan - W2DLC

Can you use electrical tape?

There is a small possibility that the power supply was interrupted when removing the earphones. ?The issue is more probable with earlier versions of the software (Hans added software to limit the problem). ? His test was to jiggle the power connector to cause interruptions in the supply.?

I would verify that the protection Zeners are still good for both supplies.?

73

Evan

AC9TU

Joe,

You can use electrical tape, but it's a bit thicker, so it may make it harder to align the controls with holes in the case.

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73, Dan - W2DLC

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73, Dan - W2DLC

Hi Daniel,

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D109 is the protection Zener for PCB#2, it has some failure reports, I had one failure too.

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73, Wei

Thanks Wei. I'll check that one too.

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73, Dan - W2DLC

I checked all diodes on the two buck converter boards and they all seem to be OK with high resistance in one direction and low resistance in the other. When I plug it in and push the left encoder button, it draws significant amperage while the encoder is depressed, but returns to zero when released. I can't specify the exact current draw because the meter on my power supply is not accurate at that low level, but it seems to be less than an amp..

That's all I can think to do at this point. I'm wondering if I should just order a new set of power supply boards.?

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73, Dan - W2DLC

Check the pictures out.

I had some imilar probs, but without damage. And for sure, check all other Spaces in your QMX

Forgot explanation.

Good catch! I'll look at those points because I can't seem to find any other damage.

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On Thu, Oct 10, 2024 at 11:44 AM, <dd5nt@...> wrote:

Forgot explanation.

On the first, the LCD Pins has contact to the coil, on the 2nd one, the metal"holder" of the lcd had contact to the PA.

After bending the holder and resoldering and bending the pins it still works.

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73, Dan - W2DLC

Robert,

I think Hans had made a change in the firmware with v.027 to ramp up and down any inadvertent change in voltage from this type of occurrence.? I still had v.026 on my QMX, and I suspect I damaged D109. That may be what happened to yours too.? I just got some parts this week and haven't had a chance to work on it, but I will keep this thread updated when I do.

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73, Dan - W2DLC

Update:? Success!? I replaced the power supply boards, and my QMX HB is working great. All diagnostics look good, and I updated to the latest firmware, which will hopefully prevent this from happening again.? I'm going to see if I can repair the original power supply boards next and have parts on order. I think the D109 protection diode probably faulted, but haven't given it a real test yet.

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73, Dan - W2DLC

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