Is the 74LS04 used originally or has it been a replacement for a '04 from another logic family? DId this machine ver run? The whole oscillator design seems much to low-impedant with the 2x 1k and 91ohm. 56pF seems quite large as well, but I might be totally mistaken... Here are some hints: http://splat.foo.is/electronics/osc.html http://www.z80.info/uexosc.htm http://www.linear.com/pdf/an12.pdf ftp://download.intel.nl/design/mcs51/applnots/23065901.pdf
(none of those resembles the design you have with the resistor between the two gates....) Uwe. Charles Eisnor wrote: > > Hi list members, > > I've a question on what "should have been" a truly simple circuit. I'm > trouble-shooting the electronic side of a gas chromatograph, all computer > controlled. I've got power but the clock signal is not there. Well it's there but > as a 1.3 V p-p sine wave of the correct frequency (7.09 MHz). That's not going to > clock anything. I know it must be a square wave. The manufacturer is using 3/6th > of a 74LS04 with the crystal across pins 1 and 4. There is a 1K resistor across > pins 1 and 2 , a 91 ohm resistor between pins 2 and 3 and a 1K resistor across > pins 3 and 4. There is a 56 pF cap from pin 3 to ground. Pin 4 drives another > inverter, pin 5. So the output I would expect should be a square wave of about > logic voltage from pin 6. But its not. Its a sine wave of about 1.4 Vp-p. I even > breadboarded the circuit and I'm still getting a sine wave. > > I'm quite green when it comes to crystals. So what am I doing wrong? And more > importantly do you have any suggestions on how I might square up the problem. > > Many thanks for your time. Its greatly appreciated. > > Chuck Eisnor > -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
