Here's a brief update....
While on my lunch break (my office is close to home) I decided to do a quick
test on the rig, covers on, as I only had about 20 minutes before I had to get
back to work.
I keyed the rig in RTTY on 40 (into a dummy load) for about 30 secs, 3 or 4
times. As before, power out started at 100W. Then very subtly the power began
to creep downwards on susequent keyings. I then immediately switched to SSB
and gave a few good whistles and got 100W out.
I guess we can pretty much rule out excessive heat, because the rig was on for
all of 10 minutes prior to my "testing" .... I had to do a little DXing.
The next step will be to repeat the "test" with the covers off and look for a
poorly seated board.
As always, thanks for the input
Frank, W1NK
---- GGLL <nagato@arnet.com.ar> wrote:
> Please see below:
>
> w1nk@cox.net escribiÃ:
> > Yes... all the other bands and modes (well, except AM) show 100W output.
> > What strikes me as strange is that it's *only* on 40M RTTY that the power
> > drops.
> >
> > The more I think about it, I wonder if heat has something to do with it.
> > In both instances over the weekend, I was on 40 RTTY after being on 20 RTTY
>
> So if you were operating, that leaves fqcy. instability out .
>
> > for about a good 60 to 90 minutes. Then after letting the rig "rest" (even
> > overnight) the power out would slowly creep back up (after a night's rest,
> > I got a full 100W out).
>
> Indeed, those facts lead one to say "high temperature somewhere", but why CW
> 100w?. Did you also test, whistling at mike, your pep in SSB?.
>
> Even if heat was a factor, should I see a fairly
> > consistent power drop on all bands/modes??
>
> Must be, take in care that rtty is a "heavy duty" mode, more if you work at
> full power. The problem, if due to foldback related to a high temperature
> condition may be reproduced at all bands, but worst at rtty mode. What keeps
> me "head scratching" is the fact that after foldback of power output, if you
> switch immediately to CW you get full output power!, so, at first glance for
> me, that situation would be not temperature related, because the main
> protection sensors against high temperatures are located in the PA stage.
> Perhaps another course of action would be to operate the rig with the
> cover
> off (top first, just to say one) wait for the failure and move some board
> connectors to see what happens. Could be a solder problem.
>
> Let me know what happens.
>
> Best regards
> Guillermo - LU8EYW.
>
> >
> > Frank, W1NK
> >
> >
> > ---- GGLL <nagato@arnet.com.ar> wrote:
> >
> >> Yes, because the trimmer capacitor failure could lead to a frequency
> >> shift well outside the filter passband. An erratic "note" monitored in
> >> another receiver is heared when this kind of failure happens. This is the
> >> one thing I guess is your problem because you mention that CW power out
> >> is fine (do you obtain the same pep in SSB?).
> >>
> >> Best regards Guillermo - LU8EYW.
> >>
> >> w1nk@cox.net escribiÃ:
> >>
> >>> When you ask if the output frequency is stable, I assume you mean am I
> >>> noticing any VFO drift? If so, then no, the VFO is stable.
> >>>
> >>> Thanks though,
> >>>
> >>> Frank, W1NK ---- GGLL <nagato@arnet.com.ar> wrote:
> >>>
> >>>
> >>>> Is the output frequency stable in that mode?. I suspect a defective
> >>>> part in the related oscillator; perhaps a trimmer cap.
> >>>>
> >>>> Best regards Guillermo - LU8EYW.
> >>>>
> >>>> w1nk@cox.net escribiÃ:
> >>>>
> >>>>
> >>>>> This has me truly puzzled....
> >>>>>
> >>>>> Last night and tonite during the CQWW RTTY contest, I noticed that
> >>>>> my FT-990 is folding back power only on 40M RTTY. I've watched my
> >>>>> watt meter indicate 50, then 40 then 30 watts out. Switch to CW,
> >>>>> 100 W out.
> >>>>>
> >>>>> Any other band is fine...100W out on RTTY (or any other mode for
> >>>>> that matter).
> >>>>>
> >>>>> The rig is running cool to the touch, the fan is kicking in
> >>>>> appropriately... so I assume heat is not an issue.
> >>>>>
> >>>>> Operating time seems to be a factor....in other words, prior to
> >>>>> switching to 40 I had been on 20 for about an hour or so. This
> >>>>> morning after the rig had "rested" overnight, I had 100W out on 40.
> >>>>>
> >>>>>
> >>>>> Thoughts??
> >>>>>
> >>>>> Thanks, Frank, W1NK _______________________________________________
> >>>>> Yaesu mailing list Yaesu@contesting.com
> >>>>> http://lists.contesting.com/mailman/listinfo/yaesu
> >>>>>
> >>>
> >>>
> >>>
> >
> > _______________________________________________ Yaesu mailing list
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