HI Uwe, The manufacturer's schematic shows a 74LS04 but one of my texts states that the 1K resistors should be 3K9 resistors for the LS series and 1K only for the regular series. But yes the machine worked for close to 20 years. What I described to you as the layout came right from the manufacturer's schematics.
Thanks for the website referneces. Right now all I want to do is get a clock, any design for the 7.09 MHz signal to get the old device up and running. Thanks, Chuck Uwe Zimmermann wrote: > 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). -- Charles R. Eisnor Service for Laboratory Equipment & Instrumentation http://www.scientific-electronics.com ph: 902-681-0998 fax: 902-681-1276 -- Author: Charles Eisnor 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).
