Bob - Don't be surprised that you don't see anything on the scope trace when viewing a chirpy PTO signal. 10 Hz or even a few tens of Hz will likely not be visible on an oscilloscope as it represents a fraction of a percent of the frequency involved.
The usual things to check first are: is the yoke grounded? (I believe there is a strap on the C-Line, IIRC); Is your regulated voltage to the PTO holding solid? IMO, if both of the above are okay, you may be looking at what Garey and I found wrong with my R-4A a while back - a bad silver-mica capacitor in the resonant circuit. The one that went bad in mine wasn't a typical-looking part, but a tubular one with color-coding. In the bipolar PTO, its value was about 92 pF - check your schematic. It will be the one that's in direct parallel with the coil. Removing the PTO - at least with the A's and B's - requires removal of the front panel. This is a good time to clean it as well as the fiducial window. Use only dish soap for the window or you'll take off the red line! Let us know how you make out. 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! Message: 6 Date: Wed, 26 Oct 2011 07:32:16 -0700 From: Robert Fish <rwf...@comcast.net> To: "drakelist@zerobeat.net" <drakelist@zerobeat.net> Subject: [Drakelist] T-4XC Unstable PTO (I think) Message-ID: <4ea819f0.4020...@comcast.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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
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