The Heathkit HG-10 VFO (Variable Frequency Oscillator) was sold as a kit. It uses a 6CH8 as a series-tuned Clapp oscillator and cathode follower and a 0B2 as voltage regulator. Output is 5 volts RMS open circuit. Mechanical construction of the VFO is excellent using a relatively heavy steel chassis and base plate for stability. The HG-10 requires an external source of B+ of 140 volts or more at 25 mA and 6.3 volts at 0.75 amp for filament. This is available from the accessory socket of the DX-40, or the matching DX-60 or from a small separate power supply. Heath shows a schematic of a suggested separate supply in the HG-10 manual.
A separate lighted-roller tuning scale is provided for the 80, 40, 20, 15, 10, 6, and 2 meter bands. Four actual oscillator ranges are used. The 80 meter band output is the fundamental 3.5 to 4 MHz. The 40, 20, 15, and 10 meter dial scales all use 7.0 to 7.425 MHz, the extended 40 meter fundamental oscillator output. The 6 meter band output is 8.333 to 9 MHz. The 2 meter range uses 8 to 8.222 MHz. The following link is to Heath catalog information on the HG-10
This VFO was purchased as a companion piece to the matching DX-60 . The cosmetics of this piece are original and in excellent condition.
In powering the HG-10 for testing, I used a Heath PS-4 variable power supply. As it turned out, the VFO just needed a good cleaning and thorough alignment. It worked fine. Alignment is speeded with use of a frequency counter.
I downloaded the HG-10 manual that is available from BAMA. Unfortunately the quality is very poor. The HG-10B download is much better quality. If you have an original HG-10 manual you can scan, please send BAMA a better version. The HG-10 schematic is a separate download from the archival Heath circuit site and is of decent quality.
The matching Heathkit DX-60 transmitter was the previous item on the bench.