Hi Again Steve, I forgot one thing in my previous post: I replaced the zener diode in the PTO, too (one of the very first things I did).
Result: NO CHANGE. ~73~ de Eddy VE3CUI - VE3XZ ********************************************************************************************************************* On 2011-07-29, at 7:58 AM, Eddy Swynar wrote: > Hi Steve, > > I've been reading the posts re. your "progress"(!) in this maTTER with great > interest, because your experience basically mirrors that of my own here in > the matter of the PTO travails that I continue to have with my T-4X > transmitter... > > To summarize, here's what I did with mine in hopes of finding a final "cure": > > ---I allowed the rig to warm-up for a minimum one hour before using it on the > air. Result: the jumpiness was less prevalent after this time period---but it > was still there. > > ---I installed the "insurance" grounding strap on the yoke recommended by > Drake & others here on the Reflector. Result: no change. > > ---I pulled the plug on the external fan that I'd mounted over the PA > enclosure, with hopes that thermal instability of some kind might be the > cause of my PTO "jumpiness". My theory (hope...?!) was that the PTO wasn't > getting proper;y "heat soaked" in my cool basement environment, and that by > allowing everything to properly warm-up, the problem would be gone. I even > wrapped the T-4X with paper for better heat retention. Result: no change. > > ---I "gasketed" the entire bottom periphery of the PTO enclosure with > aluminum foil & tape to better ensure the integrity of the "sealing" of same. > Result: no change. > > ---After dis-assembly of the PTO board from its moorings, I detected COLD > SOLDER JOINTS on the main (large) silver mica capacitor. I replaced this cap > with TWO brand new S.M.'s in parallel (each being twice the value of the > original, of course). Result: no change, although the rate of occurance was > less. > > My latest finding was this: in one extensive operation on the air recently, > the frequency stability became REALLY bad---and STAYED that way, continually > (a GOOD thing, really, as few things are as vexing in trouble-shooting as > "...intermittants"). Not having the cover off of the rig, I "probed & poked' > the yoke of the PTP drive with a long wooden chopstick & found that I could > affect the instability by judicious application of pressure of the stick! > > This does NOT seem right to me, and leads me to suspect---in my case, > anyway---that another complete tear-down of the PTO "works" is in my future, > to be followed by a THOROUGH cleansing of everything in sight that moves with > a wash of isopropyl rubbing alcohol & Q-tips...no guarantees that this'll > work, either, of course---but hope springs eternal. > > Your sad experience with replacing the transistors affirms in my mind that I > should NOT take that same route with my PTO here, and that the issue is---as > is the case with so many things in radio & life!---probably the result of > something extremely trivial (on first glance) that would most likely be very > easy to fix, and consequently, is readily overlooked... > > ...But as I say, hope springs eternal! Hi Hi > > ~73~ de Eddy VE3CUI - VE3XZ > > > ************************************************************************************************************************* > > > On 2011-07-28, at 9:07 PM, Steve Wedge wrote: > >> Replaced both transistors - the osc with the correct 2N706A and the buffer >> with a 2N3904 (the '3858's are no longer made and the ones left are >> stupid-expensive). >> >> Unfortunately, it's still jumping around like a five-year-old on a >> sugar-buzz. Scratch the transistors as the culprits - though the signal >> quality does sound a little better. >> >> Looking at the worm drive/yoke, I'm wondering: how much slop is >> acceptablebetween the worm drive and the yoke? Mine seems to have a >> significant amount. >> >> I'm also tending back toward capacitors again. that largish brown one: is >> there anything "special" about it? I've heard at least a couple of reports >> of that being the culprit. >> >> 73, >> >> Steve Wedge, W1ES/4 >> >> "I can't complain, but sometimes I still do." >> - Joe Walsh >> >> If the above message appears, it came from Steve's Son of Laptop! >> _______________________________________________ >> Drakelist mailing list >> Drakelist@zerobeat.net >> http://mailman.zerobeat.net/mailman/listinfo/drakelist >
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