Electronic – I have a question in designing crystal oscillator

With the details provided, it does seem like the crystal may be damaged - it's the most sensitive component on the board, and there's a good chance the pulser has been dropped a few times during it's long life.

The circuit seems reasonable and if it was originally designed with the resistor (rather than the capacitor), then I'd leave it like that. There are similar circuits out there that do use a capacitor as you say:

I'd go for replacing the crystal - choose a crystal designed for series operation such as the FOXLF160 (as opposed to the FOXLF160-20) While you're grabbing the crystal, getting a couple of 74LS38s wouldn't be a bad idea either, given they are only around 50 pence/cents each.

Also, given the price of decent CMOS oscillators nowadays, the other option is just to buy a 16MHz CMOS oscillator (5V supply tolerant) and replace the first stage with that.

1. Crystal, or quartz crystal. Crystal resonator is not at all incorrect but they have been called just crystals for over 50 years to no harm...

2. Ceramic resonator; maybe just resonator, but certainly not crystal or oscillator.

3. Basically yes. (The middle terminal will be ground). However there are also ceramic filters with this configuration, so be careful and double check the datasheet. (Especially if they are marked with common radio IF frequencies, 455 kHz or 10.7 MHz!)

4. I don't know; most likely no.2 in different packaging, I have never seen quartz crystals packaged this way.

5. Yes.

6. No, though connected to the right pins on an IC it might be. A crystal oscillator is either:

   a. something like package (1) with 4 pins; it takes 3.3V or 5V in, and puts out a clean signal (making it dead easy to use), or

   b. a circuit involving these components, possibly a resistor, and some kind of amplifier (inside the IC, or a separate transistor) or a misused logic gate, to drive the crystal. In the latter case you can usually substitute a ceramic resonator, but you may have to change the capacitors and a gain setting resistor (or drive limiting resistor) to make it work at all, or work reliably.