Hi Guys, Not intending to flog a dead horse here, or anything, but I do feel compelled to let everyone in on my latest---and hopefully FINAL!---attempt at taming the squirrely PTO in my T-4X transmitter...
Last week I extricated the PTO board from its enclosure & mounts, and I outright replaced each & every fixed resistor associated with the oscillator stage itself. I used "fresh" 1/4-watt "flame proof" resistors that I purchased out of a place in Toronto. The theory behind all this was simple enough, i.e. if 40+ year old capacitors can change with age, then why not 40+ year old carbon resistors, too---especially when they're under load? Surely even a MINUTE change in an aged resistor's value could have a noticeable effect on the stability of a solid-state oscillator---especially if said resistor is in a lead connecting the transistor to its source of voltage, right...? Anyway, some 10, or so resistors later (I got bleary-eyed from focusing on the small components!), I re-assembled everything, and have been testing the transmitter for a week now. The previous oh-so-gradual creep in the PTO's frequency---and the resultant sudden drop back to the original frequency---has disappeared. Ditto the sudden & "unannounced" frequency jumps of 1-2 KHz. There is no more warble, either... I guess the point of posting this is two-fold: firstly, if you're plagued with an unpredictable PTO as i was, the final "fix" can be two-fold, three-fold, or even more! Secondly, whenever I've posted my past "successes" in this regard on the Reflector, the T-4X has ultimately & consistently proven me to be a liar! Hi Hi. Let's see if I might get fooled again with this one... ~73~ de Eddy VE3CUI - VE3XZ _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
