and check for DC continuity (zero resistance). If you do not get zero resistance, then either you
have installed the wires in the wrong holes, or you have failed to burn off all the enamel and
achieve good joints to the wire. Fix it before proceeding!
Next repeat the cut/tin/solder procedure for wires T-1 and B-1. Check with a DVM for DC
continuity between the right-hand pin of transistor Q1’s three pads, and the wiper pin of trimmer
potentiometer R5. R5 has three pins and the “wiper” pin is the one just to the left of the + symbol
on the PCB silkscreen. Again – do not proceed until DC continuity (zero resistance) is seen here.
Finally repeat the same procedure for wires T-0 and B-0. Check for DC continuity between the left
pin of Q2’s three pads, and the same wiper pin of the trimmer potentiometer R5.
If all is well, this is the most difficult parts of the assembly over, the rest is relatively easy; you
should now have an assembly that looks like the photograph below. Note that in the photo the blue
low pass filter capacitors have been installed, which yours will not have yet (this was for
measurement purposes of the LPF characteristics).
3.8 Install Low Pass Filter capacitors C14 and C18
These two capacitors are 250V NP0/C0G types. The capacitor value depends on the band the
50W PA kit is being built for, as follows:
Band
Value
Code
80m
270pF
“271”
40m
270pF
“271”
30m
270pF
“271”
20m
180pF
“181”
50W QCX PA kit assembly
1.00q
19
