Mechanical maintenance is just as important as electrical.
The tuning dial was stiff. The HSB-133 uses a dial cord to move the tuning gang and the pointer. Old grease had turned to glue. I cleaned the pulleys and the shaft with isopropyl alcohol and applied a light synthetic grease to the shaft bushings. hsb133 receiver work
For the controls, I sprayed DeoxIT D5 into the volume and tone potentiometers and exercised them (rotated them back and forth 20-30 times). This cleared up 90% of the static crackle. Mechanical maintenance is just as important as electrical
This is where Heathkits often show their age. The FM reception was weak and mono-only. hsb133 receiver work
This is the most critical phase. The microcontroller performs three checks: