Thanks, Martin.....glad you “stumbled” on the problem, whilst
looking.....sometimes better to be lucky than good ;-).
Greg, KC8HXO
Sent from my Linux device
> On Apr 23, 2018, at 00:08, Martin Sole <hs0zed@gmail.com> wrote:
>
> Orion 565
>
> Hi,
>
> I noticed yesterday that I had very low power on 160, 3-5 watts, low power on
> 80, lower power on 60 and lowish power on 40, 30, 20 and 17 were all pretty
> normal though slightly down on what I recalled, 95 vs 105 watts on 20m. Power
> on 15 12 and 10 was also down, 60-70 watts.
>
> So a somewhat frequency sensitive power problem.
>
> I started by pulling the drive cable J5, low level TX out, from A3-81906 RF
> converter. Measuring the drive at this point I used the direct input mode of
> my LP-100A power meter and registered around +25dBm on 17 but less on other
> bands, down to around 5dBm on 160. Working back to the input of A3 at J3 I
> measured approximately -5dBm on all bands. From this I started to focus on A3
> and examine in more detail the signal path. As I'm trying to identify parts
> against the schematic my probe touched on R119, the TX mixer balance pot,
> which I couldn't immediately see on the diagram. As I touched it the 160m
> drive power jumped to +24dBm. A check of the other bands showed them all to
> be roughly similar. Reconnecting the PA I now have full power on all bands. I
> have given R119 a bit of a workout and reset it for minimum LO feedthrough.
>
> R119 is another of those blue pots, as found throughout the radio and as
> others have noted can be the cause of problems.
>
> As the radios age and as the pots start to suffer more and more, or so it
> would seem, a reliable replacement would be good to add to the first aid kit.
> Some of this could be attributable to my environment, Thailand is super
> humid, YMMV.
>
> Thought I would post this in case anyone else runs into a similar issue.
>
> Regards
> Martin, HS0ZED
>
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