Hi again,
[Forgot to mention: I jumpered across this filter (from D41 to D36) with
a 0.01uF capacitor and the receiver came to life on 40 and 30 meters, so
this latest problem is definitely in the bandpass filter section
attenuating the LO too much.]
73
Phil
On Wed, Feb 20, 2019 at 11:43 AM Phil Erickson <phil.erickson@gmail.com>
wrote:
> Hi all,
>
> (I hope someone else someday can make use of this VI+ debugging
> information..)
>
> I'm still troubleshooting my VI+, which you can follow by searching the
> archive. In particular, I'm still figuring out why the XO/LO board has low
> output drive for the LO on some bands (160/80/40/30), subsequently causing
> the BPF mixer to never turn on.
>
> Right now, I'm focusing on the 40/30 meter bandpass filter section after
> the U1 mixer but before the amplifier (Q6,Q7,Q8) and output. There are two
> tunable coils, L1 and L2. Under the microscope, at least one of these is
> definitely broken at its base and I'm sure that results in a very mistuned
> filter, which is what is causing my attenuation problem. I need to replace
> it and possibly more - someone was obviously in here with a 'golden
> screwdriver' as we found epoxy as well. The adjustable coils are really
> bad mechanically and the core wobbles a LOT when you move it with your
> finger - easy to break.
>
> But Ten-Tec's schematic has no values of the appropriate inductance
> range :( Ugh.
>
> Does anyone (Gary? Peter?) have info on the designed range for L1 - L11
> for the bandpass sections on that board? I can't find it anywhere on the
> schematic and the manual doesn't say either. It's bizarre that they label
> some things but leave this out (?).
>
> Cheers/73
> Phil W1PJE
>
>
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