Building the QCX Mini: What Tools do you Need?

QCX Mini Troubleshooting and Repair Tips

QCX Mini: C38 Retrospective, and some Troubleshooting

If you’ve been following along on my YouTube Channel, you’ll find that I’ve been having issues getting any sideband cancellation with my QCX Mini. I’ve been troubleshooting it. See the video below for some information about the troubleshooting. But first, remember C38?

C38 Woes: Root cause found!

On a few QCX Mini’s, C38 blew, causing the 5V regulator to short, which rendered some brand new radios inoperable. Some were quick to blame the switch to SMD parts or to go a bit overboard with their accusations. But Hans did some forensic work, and found the cause, mentioned in This Thread on the QRP Labs page.

The cause? The factory used a part rated for 10V, not the 25V part that Hans specified in the Bill of Materials! With higher voltage, capacitance goes down, and failure ensued. Hans has made it good and anyone who lost a QCX Mini is being taken care of. All kits are being shipped with the requisite 10uf capacitor so that this doesn’t affect others. The next batch of boards will use a through-hole part.

QCX Troubleshooting

Here’s the video I mentioned at the outset. Please have a look and let me know: What do you think might be the cause? The more brains the better. Comment here or on YouTube. Thanks and 73!
Also, if you haven’t already Please subscribe to the YouTube Channel. It’ll really help me. Thanks for your support!


    • Bob AC9MG on February 17, 2021 at 11:44 AM
    • Reply

    I viewed your YouTube on troubleshooting the qcx mini. It looks like my problem is in the op amp sections also. I could not do any receiver alignment because the bar graph would come on for a fraction of a second and then disappear when adjusting the bpf and all the other alignments. Anyway I think I found it while checking the amp op dc voltages. The problems start in IC7. Iā€™m wondering where you order the op amps from, mouser perhaps?
    They are the OPA2277 smd chips.
    Bob AC9MG

    1. Hi Bob, I didn’t use OPA2277’s, I used NE5532’s instead. They are SOIC8 packaged chips. I ordered mine on for about 70 cents a piece šŸ™‚ Good luck with the fix!

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