Help with getting an old Quartz resonator going - Page 1
Forum section: electronics / beginners

author: iamseth
author_rank: Newbie
timestamp: December 10, 2024, 03:42:35 pm
content: I picked up an old Quartz resonator from Ebay. This morning I started on a Pierce oscillator to bring it to life though I can't figure out which values I ought to use for R1, C1, and C2.Ordinarily I'd just try things until I got it working but I'm moving more carefully because the resonator has sentimental value and I've read that the feedback might cause damage.My goal is to just get it ringing and graph it on a scope.The part was produced by a family member's outfit I'm guessing anywhere from 1930 to 1950 and I haven't been able to find a datasheet on it.This is the Ebay location with some pictures of the component.https://www.ebay.com/itm/267042258669Any help greatly appreciated.

author: Smile2016
author_rank: Regular Contributor
timestamp: December 10, 2024, 04:23:19 pm
content: I would start with 4.7Meg + 2x 22pF. A schematic would help. Without a datasheet you can use a cheap VNA [you can get a NanoVNA-H4 from Amazon before Christmas ~ 50-100bucks ] to get resonator's parameters....

author: edavid
author_rank: Super Contributor
timestamp: December 10, 2024, 04:40:59 pm
content: Yes, please post your schematic.You may have to open the case and clean the spring contacts. These old crystals are not fragile.

author: iamseth
author_rank: Newbie
timestamp: December 10, 2024, 05:08:23 pm
content: QuoteI've attached a image of a schematic with what I thought would be a basic way to get it to do something interesting. I bought the linked VNA just now. Should be here in 8 days. Thanks for the recommendation.QuoteThanks for the tip. I'll crack her open later. When you say not fragile, do you mean not easily physically broken, electrically, or both?

author: edavid
author_rank: Super Contributor
timestamp: December 10, 2024, 05:25:38 pm
content: What is the part number of the inverter IC? 4.7K seems too low for CMOS and too high for TTL.It should oscillate without the capacitors.QuoteBoth.

author: Smile2016
author_rank: Regular Contributor
timestamp: December 10, 2024, 05:26:20 pm
content: Resistor should be MegaOhm magnitude not KiloOhm... so 4.7..10MegaOhm range...CMOS

author: CaptDon
author_rank: Super Contributor
timestamp: December 10, 2024, 10:50:12 pm
content: What inverter are you using? What is the frequency of the crystal? With a CMOS or TTL family inverter you can't possibly hurt the crystal. They were used in vacuum tube oscillators that pushed as much as 10 milliamps of crystal current. You may have better luck using a 7404 or 74ls04. Two gates as the oscillator and wire the remaining gates in parallel as a high drive capability buffer. 4.7K is a sensible value for a 7404.

author: edavid
author_rank: Super Contributor
timestamp: December 11, 2024, 03:13:54 am
content: Quote from: CaptDon on December 10, 2024, 10:50:12 pmPhoto shows 1.043 MHz.QuoteNot really, since the input current can be 1.6mA.

author: Zero999
author_rank: Super Contributor
timestamp: December 11, 2024, 09:15:12 am
content: Assuming it's CMOS, use an unbuffered gate i.e. 4069, 4007, 74HCU04, rather than the 4001, 4011, 74HC04 which are all buffered.Buffered gates have three amplifiers in series, which can form a ring oscillator, causing it to oscillate at a much higher frequency.I recommend an IC specifically designed for this such as the, 74LVC1404 or 74LVC1GX04, which have an unbuffered gate for the oscillator, followed by a buffered gate to isolate the load from the oscillator.https://www.ti.com/lit/ds/symlink/sn74lvc1404.pdfhttps://www.ti.com/lit/ds/symlink/sn74lvc1gx04.pdf

author: CaptDon
author_rank: Super Contributor
timestamp: December 11, 2024, 03:08:50 pm
content: eDavid, ever looked at any of the older arcade video games from Atari and such? They used standard 7404 since LS was not yet common and I have seen anything from 2.2K to 4.7K. The inverter will force itself into a linear area which makes oscillation possible. Calculations based on 1.6ma are meaningless when you want to run a logic device in a linear area. With the 2.2K or slightly higher the inverter is forced into a 'gray' undefined state and the crystal's phase shift combined with the unstable operating area of the logic device creates the frequency sustaining oscillation. Often these circuits work well with 3rd overtone crystals and you have to be careful because sometimes a fundamental circuit will suddenly shift to the third overtone!

author: edavid
author_rank: Super Contributor
timestamp: December 11, 2024, 03:30:11 pm
content: Quote from: CaptDon on December 11, 2024, 03:08:50 pmThe attached Altair 680b oscillator is the kind of circuit I remember using, with 470ohm resistors across the TTL inverters.Too bad we seem to have lost OP