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I suggest? that Assume the amp will draw current? equivalent to? the? A for Watts = 2 x power out expected? (your guess ) then select a fuse 20% higher

That will provide a back up for any current limiting? (or not) it seems not in your power pack.?

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The fuse may or may not? save the mosfets if? something goes south.? But will protect most other components.

These? IRF 510 amps from Hans don't have a reputation for thermal runaway.??

BTW on sport aircraft like sail planes, the? fuse is often put Right on the battery terminal.This can save a lot of tears later - esp for lithium based batteries.

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TEF

As Ron said whenever there is a serious VDD to GND short, it’s usually less than an ohm. ?On all the rigs I’ve fixed, it was about .4 ohm. I always build a QMX or QMX+ so that I can test the cpu very early in the process. ?I install the power connector, the 2 SMPS boards and the whole front panel. ?I power it up at 6.1 volts and load firmware. ?

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73
Jeff Moore
W1NC

Thanks Chris and Doug. I did short it to ground when I completed the build and noticed the issue and confirm that this did turn it on but the ability to turn it off would be nice also.

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Somehow I overlooked the part number on the schematic, I confess I did look several months ago but didn't see it then and I have not looked since. Sometimes we don't see the obvious in front of us I guess. Thanks again?

Today's firmware update to 1_00_023 ended up successful, but had me worried for a bit.

Everything seemed to go OK until this happened: My windows file copy software does a consistency check after every copy and when I copied the _023.QMX file, it read the copied file and responded with "hash mismatch." Then it quit, and so did any indication of the QMX being a Windows file system. [In hindsight, this makes sense because reading the loaded QMX is really not like reading any other file, and Hans tells us in the Ops Manual that it's not really like any other Windows file.]

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The BOTHERSOME thing was that the QMX wouldn't start up. I pressed and held the left/VOL encoder several times. Nothing... I tried the USB cable again. Nothing... Then, I wondered if Hans had implemented some alternative way of starting a non-responsive QMX.? Hmmmmm?

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I pressed both encoders at the same time and VOILA! it started.

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THANKS Hans! ... or, maybe I was drinking? I had only one beer with lunch.?

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72 de N4REE, Bob Easton - QRP CW forever

P.S. I am constantly amazed by this tiny little radio!

Mark, 9K is what most are seeing, but my brother recently measured his brand new QMX+ board out of the bag and found 262R Vdd to ground. He installed the DC input connector?and the two power supply boards and temporarily shorted the PWR ON point to ground and the thumb drive came up on the computer ready to accept firmware. It seems the MCU Vdd short to ground measures 1R or so when it's there. So he continued his build (still in progress). Not sure why it has the lower than normal resistance on Vdd but it isn't the MCU in his case. Seeing 916R you can probably proceed, but you might want to do as he did and verify the MCU is OK before investing all the time in building it... Good luck .. 73 .. .Ron

Hi Allison

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Thank you for your advice.

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BR

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Chris

Hi Chris,

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How do you get past the initial SMPS fault that stops the QMX at the hardware diagnostics screen?

My QMX stops when the firmware determines that the boards are not present as described in the manual:

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I ordered replacement SMPS boards a few days back and I want to get a head start on any additional troubleshooting that may be needed for the rest of the transceiver while I wait on the order.

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73, Mike KK7ER

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WARNING - WARNING

To all Ham Husbands

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Please activate the Groups.IO Spy Filter before it’s too late!!

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Dave ve3zzy

Thanks. Don't know why I couldn't find it. Oh well...

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73...? ? ? Mark? ? ?AA7TA

Doesn't it also prevent the QMX from saving current settings? If so, then you would not save frequency, etc. and when you turn it on again, you'd have to input everything again.

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73, Dan? NM3A

@aa4ha Thanks for explanation.

Yep, that is what I used to do as well. It is a dirt cheap and easy solution.

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I had a radio that had the same style plug on the front panel that was for the CW key and the headphone and CW key plugs were right next to each other. Accidentally plugging the headphones in to the key jack was similar to the sound of a gun going off next to my head. I added a capacitor in series to keep DC off of the headphone coils (and to keep from keying the radio) and a pair of back to back diodes to stop the "POP!".

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Tisha, AA4HA

I can see why it might be defaulting to the channelized scheme; In the US we are not allowed to VFO across that band and must stick to channelization since we are secondary users on what is primarily a government allocation for us.

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There have been a couple of attempts for US hams to petition to change for more channels and/or VFO operations but that but it is complicated because amateur radio in the US is regulated by the FCC but government operations is regulated by NTIA (National Telecommunications Information Administration) and the two agencies do not play well with each other.

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Much of the rest of the world has a much more 'relaxed' view of the 60 meter band.

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73, AA4HA

"We have eyes everywhere....."

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Reminds me of that sports betting commercial:

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"We are everywhere, we see everything."

On Sun, Aug 4, 2024 at 07:46 AM, Manfred DL9XX wrote:

But I'm surprised that this standard measure isn't included in the original design.

The software seems to handle most things well so I suspect it's not really an issue until the encoders start to age a bit

On Sat, Jul 13, 2024 at 10:51 AM, John Z wrote:

With focus on the 20m LPF, I suggest checking the inductor leads first. A poor joint that is the result of inadequate enamel removal can wreak havoc.

I simply looked at the schematic and Q301 is a BSS123.? I would replace with the same.

21V is within acceptable starting value.? ? Also it will drp soon enough

in use to be under 20.

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Allison
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Post online only,?
direct email will go to a bit bucket.

Hi Guys

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Thank you for the data.

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The two replies are close enough to provide sensible guidance.

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I am going to use a repurposed lipo tool battery. Ie 21 V fresh off the charger and 18.5 V for most of the discharge cycle.

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I will use a couple of diodes in series between 21V and 20V to burn off the excess.

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I will set the bias for 20 V.?

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BR

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Chris