Quartz Crystal Tester

An ohmmeter or capacitance meter will not measure anything across a quarzt crystal, since it will have a resistance of several megohms (MO) and a stray capacitance of only a few picofarads (pF) — regardless of whether it's working or not. So the only solution available to us is to fit the crystal into a circuit, i.e. an oscillator, and see if it oscillates or not. This is just what our tester does — and at a ridiculously low cost.

Resistors
R1 = 22kOhm
R2 = 1 kOhm (corrected value w.r.t. printed edition)
R3 = 680Ohm (corrected value w.r.t. printed edition)
Capacitors
C1 = 1nF
C2 = 100pF
C3 = 2nF2
C4 = 10nF
C5 = 100nF
Semiconductors
D1, D2 = 1N4148
T1 = BF494
T2 = BC547
LED1 = LED
Miscellaneous
Socket for HC6/U and/or HC 18/U type xtal