Hi Bob, My PTO is from a T-4X transmitter...
My most recent "fix" to it was the complete replacement of all of the frequency determining capacitors in it (the bad solder joints were all dispatched earlier, one by one). I recently took to monitoring the actual PTO signal on a separate general coverage receiver, as well as the final "spot" signal on another: in BOTH cases the frequency will jump, indicating that the fault lies within the PTO itself. The latest "incantation" happens like this: both signals sound great for a long time---but then suddenly they will rise EVER so slowly. And then, pop! It'll go right back to the original frequency. This will go on for upwards of a half hour, or so, and then very suddenly, bang---both frequencies will go (or down) almost 2-KHz. My attention to the thing has been temporarily diverted by other things, but I have the PTO out of its mounting, & have ID'ed all of the resistors that are part of the PTO oscillator transistor itself. I am hoping to replace ALL of these resistors with factory fresh new ones, going on the assumption that these rascals are (ONE of them, anyway) is changing "under load" ever so slightly, enough to affect some critical voltage in the stage, screwing-up the stability... Gosh, I've tried just about everything else...! ~73~ de Eddy VE3CUI - VE3XZ ************************************************************************* On 2011-10-26, at 11:48 AM, Robert Fish wrote: > I know Eddy, I was going to mention your recent adventures in my opening > post. > Does it sound like the same issue your PTO had? yours was in a R-4 or R-4A as > I recall, not that it matters. > There was something about a dogbone cap in the PTO. Maybe I should go back > and read that thread, eh? > > Bob K6GGO > >> Hi Bob, >> >> Don't even START me on this topic!!! : >) >> >> ~73~ de Eddy VE3CUI - VE3XZ >> >> >> >> ********************************************************************************************************* >> >> >> >> On 2011-10-26, at 10:32 AM, Robert Fish wrote: >> >>> Hi Guys, >>> >>> I have been ignoring an issue with my T-4XC until recently. When I use the >>> R-4C PTO to control the receiver it seems to work fine. >>> When I use the T-4XC PTO to control the receiver I get sort of a chirpy, >>> jumping around of the cw signal I am trying to copy. Both >>> units >>> work fine in transceive using the R-4C PTO, which is the way I have been >>> using them. But with the recent DX expeditions (T32C, TX7M) >>> running split, I have been having to use the C-line as separates to work >>> them. I have had some success working them, but heaven knows what my signal >>> sounds like. >>> >>> I have been putting off fixing this problem as I felt it was probably the >>> PTO and I haven't been in the mood for performing major surgery lately. >>> I decided to get off my arse and do something about it yesterday. So, I got >>> out the scope and took a look at the T-4XC PTO output while it was >>> controlling the R-4C. >>> It seems stable. So I looked at the Plate of V-8 with the scope, I have a >>> composite signal (PTO, Xtal Osc.) it looks solid as a rock. So then I >>> looked at the injection signal >>> right at the jack on the back of the T-4XC and once again, I can hear a cw >>> signal I tuned in on the R-4C jumping all over the place, while I'm looking >>> at a rock solid injection sig >>> leaving the T-4XC. I switch back to the R-4C PTO and the jumping around >>> stops, the receiver copies the same cw sig with stability. >>> >>> What am I missing here? It is hard to fix something when it seems like the >>> only evidence of a problem is coming out of the speaker. If I could find >>> some evidence of the problem >>> I could follow it to it's source. This could be operator error (probably >>> is) I only put about an hour in to this last night as I got called to >>> dinner and a man has to have priorities. >>> >>> I am going to dig in to it this morning, I will eventually find the >>> problem, but maybe you guys can save me some time. >>> >>> Oh........another clue: When I use the spot function, in CW mode, I get a >>> warbling sound in the R-4C instead of a solid cw tone when tuning in the >>> T-4XC sig with the receiver. It seems >>> sort of intermittant (it switches to a cw tone sometimes and then goes back >>> to warbling like you get in SSB mode with the spot function.) >>> >>> Thanks in advance, I hope this long winded post made sense. >>> >>> >>> Bob K6GGO >>> >>> >>> _______________________________________________ >>> Drakelist mailing list >>> [email protected] >>> http://mailman.zerobeat.net/mailman/listinfo/drakelist >> >
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