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Maybe D103 has open-circuited in the fault scenario? If 3.3V from the linear regulator fails to come up, the processor does not start and the PWM regulators never run. JZ

John, While holding down the left encoder for power on, I do get the +12V out of the 5v board and into the 3.3v board. I also so 0.75v from LIN_REG_EN while holding the encoder down.? Q202 fires as

I was out of town last week, but got to take a look at the QDX again today. I found a manufacturing defect that was the source of the problem, and fixed it. The fault was indeed with inductor L16,

Just an observation for later (when you're down to the fine tuning issues): My QMX arrived Thursday, finished building it by Friday morning and have been testing it since. Am currently exploring (and

John, Nothing gets hot, as nothing turns on.? I checked the switch on the left encoder, and it still closes when pressed.? And as long as I hold it down, I see about 10mA current drain.? But

Me, too.?I should be working 20 m with QDX #2 right now. Instead, I'm sitting here fiddling with QDX #1. I released the genie of the radio from said QDX trying to figure out why it was only putting

Yes… don’t ask how I know. Mike WM4B Sent: Saturday, July 29, 2023 3:31 PM To: [email protected] Subject: Re: [QRPLabs] QMX died in first test run Useful info, thanks guys. Would

Walt, The datasheet for the processor says that its GPIO pins can source or sink up to 20 mA. A dead short to ground would burn 66 mW ( 20 mA x 3.3 volts). That isn't that much and I don't think

Useful info, thanks guys.? Would turning it on, then plugging it into the QMX help? Chris

It is always safe to add a delayed relay to activate dc power output after powering on supply. 73 Barb WB2CBA

Hi Andy, Thanks for your advise. I think it’s the best thing to do! Hans Merz / Pa3AAW

Hans, In the configuration of the U3S is a setting for "checksum" this prevents a corrupted NMEA sentence from changing the locator. But it can not be set if you want to send your locator mobile. 73

Dan Yes, a long time ago I made up a voltage/switched current limited supply from parts I had and data sheets. The only problem was the high voltage pulse at switch-on. I still use it and still

John, I was poking around with one of the scope probes, thinking I had all else disconnected.? But I still had my dummy load connected with one probe still connected to it.? While poking around, I

Walt, Sorry to hear about the boot problem! All else you mentioned seems good. The drop from 12 to 10.5 on transmit at C506 is a little unexpected but I can't see that as the root problem. The PIN

John, The voltage across C506 looks clean during transmit; it does drop from 12V to about 10.5V during transmit, but shows no oscillations. I did use the hardware test utility in firmware 1.0.6, and

Tnx 20m QRPpp QSO, KY3G ! 72, Bill, N4QA

Yes, that's me.? :-)

Just FYI: There has been the same discussion on the missing 5.1k USB C resistors for the data communication issues USB C - USB C of the NanoVNA in 2019 (!), see the thread around

Hi Hans, I think that I'd perform a reset and start again but make sure that you record all of your settings first. Andy -- The universe is made up of Protons, Neutrons, Electrons but contains only