Quartz Crystal Tester

This unit was built years ago when there was a need to test surplus crystals. It also came in handy as a signal generator for receiver alignment.

It's basically a Pierce Oscillator Circuit which works even with low-activity crystals.

Quartz Crystal Tester
'Octal' and '807' valve bases were wired for vintage crystals in addition to crystal holders suitable for HC-6/U, HC-18/U & HC-25/U crystals.

Quartz Crystal Tester - Schematic
The indicator is a 6V 0.06A dial lamp. Tuning / Loading is done using the PVC-2J 500+500 pf variable. The 2000 pf is switched in parallel for very low frequencies.

Quartz Crystal Tester - Inside view
This tester works in the range 455kHz to 20Mhz, with overtone crystals oscillating at their fundamental frequency.