HX108-2 7 Transistor AM Radio Kit - Audio Sections

K7QO HX108-2 AM Receiver: Theory and Construction - Part 03 HX108-2 Audio Sections

Schematic of the components of the AUDIO sections to be  installed on the PCB (Yellow highlight)

Figure 1: Part 3 AUDIO sections

Power supply connections installed in Part 1 are in the Green highlight. I also highlight on the parts list the items  I remove from the cardboard strips to show that they were installed

Figure 2: Wiring Audio Sections Complete

After PCB components were soldered (including the two audio transformers) I soldered the two yellow wires supplied to the PCB only, then I added the two yellow jumpers to connect the speaker.

Test Data Measurements - Part 3 Audio Sections

1. Current measured at TP5 = 12.2 mA (4-10 mA -suggested)
2. Current measured at TP4 = 4.7 mA (2~5 mA -suggested)

Current is 2.2 mA higher at TP5 than suggested maximum value.

Current at TP4 is just below the suggested maximum value.

I will solder bridge the traces at TP5 and TP4

I will cautiously continue to Part 5 Band Pass and Demodulator Section

In Part 4 Chuck Adams K7QO Analyses the circuit for the excessively high current in the Audio sections of his build.

Figure 3: Top side PCB with Audio Sections Installed

In Figure 3 I show the Audio sections installed. Please note I have marked over the Chinese character for B2, B3, B4 and B5 with the initial for the color painted on the core slug,  Also note the line on the volume control thumbwheel. In the 7 O'clock position the switch K is OFF.

73, AB1OP Ralph