开云体育

ctrl + shift + ? for shortcuts
© 2025 开云体育
  1. QRPLabs
  2. Topics

QMX: Kit build trouble, a short between A & B for Step 17 of Section 2.9

 

I started building QMX following the instructions carefully. I've been checking the solders in every step.
Installed the transformer T501, checking the continuity between the A points were fine as well as the continuity between the B points.
However, when I checked between A points and B points, my DMM shows about 370 KOhms.?
I guess I must have a short somewhere. :(
I've been using a digital microscope to verify solder bridges on the way, and did visual inspection, but I cannot find anything that could be shorted.
Any suggestions on how to troubleshoot this?
I am about to brute force troubleshoot by desoldering one by one while checking the continuity.
Thank you in advance.
 

370 kOhm as in kilo-ohm? That's the opposite of a short. Installed in the circuit, there is about 10k of resistance between the primary and secondary windings of T501 because the primary is connected to ground through R508/9 and R525/6, and the secondary is connected to ground directly. This is the peril of trying to measure any component in circuit, because you're not just measuring the component, you're measuring the circuit around it too.
 

According to the assembly manual it says "Finally, there should be NO connection between A and B. Hold one probe on any A point and the other probe on a B point. That should read infinite resistance (no continuity)." But my DMM measured 370 kilo Ohms between the ground (B) and the Q505/6. It is tricky to measure the resistance/continuity on such a tiny board.?
?

1 - 3 of 3