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Steve, is this action noted on all bands? Or only one, namely 40M? The oscillation on 40M occurs up in the 9- to 10-MHz range so the TX LPF may attenuate the signal sufficiently to not indicate on a Wattmeter. Use a spectrum analyzer to "sniff" with a loop in the LPF section while this is happening.? SAs aren't as expensive as in the old days. Even the "Tinysa Spectrum Analyzer" is available for $60-$70 on Amazon and will do your cooking proud. 73, Bob K9JU Maryville, TN
On Tuesday, April 23, 2024 at 12:30:53 PM EDT, Jim Shorney <jimnu0c@...> wrote:
Find out where the meter spike voltage is coming from. If it is from the wattmeter sensor you may have a parasitic oscillation. If it is coming from the 2nd IF/Audio board there may be a timing issue. Which version board do you have? If it is a real TR7A you should have version 2, which has all the fixes. But with board swapping and "A" version fakery you never know for sure unless you look. The version 1 IF/Audio board had some problems that were fixed by factory mods. Very old boards in the field may not have all of the mods. Check the values of R1186 and R1187. The schematics say 10K but I have seen values as low as 1.5K in the real world. Lower values will reduce the T/R turnaround time. You might also check C1151. How does your CW look? The CW generator is a crystal circuit on the IF/Audio board. It is a bit finicky to get right as Floyd K8AC found out. See his article about TR7 key clicks on HFN. The VOX and T/R control magic happen on the TX Exciter board. You may want to check for marginal electrolytics there. Also check the +10T and +10R for proper switching. It should be a reasonably fast transition between +10 and zero. 73 -Jim NU0C On Tue, 23 Apr 2024 13:40:58 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: > Whilst we are in discussions over wattmeter readings and so on, I¡¯ve had a chronic anomaly with my TR7A and its wattmeter in CW mode. > > When I transmit on CW, upon release of the key, the meter swings to the right peg. Then we have normal readings. During the time that the meter indicates maximum, there is no RF at the antenna connection (verified with external wattmeter and with a scope). > > This happens only in CW, with the VOX delay set to minimum or near minimum. If I bring the delay out to around 1 second, everything looks normal. It occurs on all bands. There¡¯s no indication in SSB or AM. > > Could I be looking at a sticky relay? I don¡¯t have a spare to swap, at the moment. > > 73, > > Steve Wedge, W1ES/4 > > Time flies like an arrow. Fruit flies like a banana. |
