[Test-Equipment] crystal checker

[Jim Wilhite]

Why not put a 10 K ohm resistor in series with the output of a signal 
generator to one pin of the crystal and the ground to the other pin. 
Add a scope across the crystal, then tune for the pattern to widen.

If you have a URM 25F like mine, I attach a frequency counter to the Hi 
RF out and read the frequency.  No pattern, the crystal is bad.

Jim/W5JO





>
> What I have used quite successfully to test xtals is a simple osc 
> using 2 sections of a TTL quad nand gate (7400). Circuit is simple:
> Pins 1&2 connect to one side of 32pf cap.
> Pins 3,4,5 connect together.
> Pin 6 connnects to one side of xtal.(this is the output)
> Other side of xtal connects to other side of cap.
> Connect 680 ohm resistor between 1,2 and 3,4,5.
> Connect 680 ohm resistor between 3,4,5, and 6.
>
> All 32 pf load parallel mode xtals should be pretty close to proper 
> frequency here. Series mode (overtone xtals) will oscillate on their
> fundamental frequency. Usually xtals below 20 MHz are parallel mode.
> Not sure how low it will work but I have tested ones as low as 1MHz.
>
>                               Bob Roehrig
>                     Aurora University    Telecom dept.
>                            broehrig at aurora.edu
>                          K9EUI  W9ZGP  WD2XSH/19
>