The analog switch is a CMOS 4016 on the parent board. It's the only IC there, hard to miss. They have been known to cause similar issues.
Replace C2108 on the Power Supply board. Even if it's not the problem. Just do it. Don't forget to check your Fixed Passband alignment when you are done. If you haven't already, you may need to re-seat one or more of the daughter boards. Oxidation in the Molex connectors can cause strange problems. 73 -Jim NU0C On Tue, 11 Feb 2014 17:59:16 -0800 (PST), Leon Zebrick wrote: >Tuning the "cal." signal and monitoring a transmitted carrier reveals a slight >frequency "warble" of sorts. PTO is clean and has the ground strap >modification, and this issue seems unrelated to the PTO, in that physical >movement or position of the PTO has no effect. This is some type of minor >instability seemingly not related to anything mechanical. Improves as rig >warms, but takes about an hour to clear. Any suggestions on how to narrow >this to the (presumably) offending oscillator? Seems like it would not show >up on a counter, but perhaps as "jiggle" on a scope? I believe I read >somewhere about an analog switch IC that can cause frequency jumping. The >frequency deviation is minor, but enough to roughen up received and >transmitted signals. Rig is very early SR#. General VFO stability is >acceptable. Could this be normal for the old rig? Thanks! >Leon (N5LAZ). -- 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://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
