On Sat, 10 Jul 2010 20:52:02 -0500, Brian Koontz wrote: >It looks like there is a comparator on the MC3302P IC that is >outputting high even though its two inputs are relatively equal >(U301D, inputs of 9.6V and 6.0V should generate a low >output...instead, it's high and appears to be keying the transmitter >via U302).
Are those measured voltages, or are you reading them off the schematic? If they are actual measured voltages, then U301-14 should indeed be low. You could temporatily ground pin 6 of U302 and see if the rig stays out of TX, that should verify U302. You may have a problem upstream from U301D in the anti-VOX, VOX, or CW keying circuits. U301 could be bad, but I would look for other causes first. Data sheet on the MC3302P is here: http://www.alldatasheet.com/datasheet-pdf/pdf/3077/MOTOROLA/MC3302P.html It looks like the outputs are open-collector, so you should be able to ground U301-13 and see if pin 14 toggles low. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://radiojim.exofire.net http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
