Further clarification of my troubleshooting steps for K2 # 5061

[M. P. Haynes]

Don, Jim, and Joe,

Over the weeks now of  troubleshooting this problem here are some of the
steps I have taken:

        * I suspected either a defective low pass filter or bandpass
filter for this band and one other. (I had damaged K7 with a soldering
iron that
           put an ever-so-small dimple in one end of the relay case.
This prevented the slide from fully engaging one set of contacts. I
replaced it and
           that band was then okay.) After replacing the defective relay
I lifted one end of W1 to isolate the two sections of filters and hooked
a
           signal  generator to the antenna connection.  I hooked my
scope to W1 and found all low pass filter characteristics as one would
expect,
           no loss of signal strength on the selected band but noticeable
attenuation on the next higher band.  I forgot to say that I had already
           reflowed all solder connections on both the LPF and BPF
circuits.  

        * I replaced C22 (2.7 pF).  

        * I hooked a jumper to the BPF test point (I had soldered a loop
of wire onto D7 cathode to prevent damaging the component leads with
           my scope probe) and could hear stations on both 20 and 30
meters.  I coupled this lead through a capacitor (to prevent shorting 8R)
and
           the signals were as loud on the two bands in question as the
other, functional bands.  

        * My friend Ron used a high quality capacitance / inductance
meter and found L9 to vary from, as I recall, about 3.9~4.9 uH with the
slug
            top to bottom. The capacitors in circuit measured
approximately their stamped values considering stray circuit
capacitances.  Each of us
            checked and rechecked the values of all components and they
were correct.  Neither capacitors nor inductor were shorted to ground
            except the ends of caps that were supposed to be.

        * I have measured contacts 2,3,4 and 7,8,9 on relays K3 and K4
and they function as you would expect from the relay truth table.  I even

           tried a relay reset (control board removed on power up) and
then rechecked with identical results.  I also have cheched that the
signal line
           (W1, W6 and BPF T.P.) is not shorted to ground on 20/30.

        * When feeding a signal from my sig generator through the coax
connector and checking at the BPF T.P. there is no noticeable attenuation

            on any bands except 20 and 30 which was down about 70 dB.

        * L8 peaks properly on 30 meters.  With the added cap acrross L9
it peaks about two turns from the top of the can.

At this point I had already decided to arbitrarily replace C24 and C25
but I don't really expect any change since they check okay with a
capacitance meter in circuit. (C19 and C20 check the same as C24 and
C25).  I am really getting discouraged at this point, but like Little
Orphan Annie sings, "The sun will come out tomorrow!"  Thanks to all for
your suggestions.  If I have an epiphany, I'll let you know!

73,

Pat-K4BEH
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[Don Wilhelm-3]

Pat,

One further check - RFC7 (15 uH) and C104 (68 pF).  This is a series
resonant circuit tuned approximately to the IF frequency - if for some
reason these 2 components are series resonant somewhere around 12 mHz, it
could reduce the 30 and 20 meter signals significantly.  As a quick check,
you could lift one end of RFC7 and see if you can tune the bandpass on 30
and 20.

73,
Don W3FPR

> -----Original Message-----
>
> Over the weeks now of  troubleshooting this problem here are some of the
> steps I have taken:
>
>         * I suspected either a defective low pass filter or bandpass
> filter for this band and one other. (I had damaged K7 with a soldering
> iron that
>            put an ever-so-small dimple in one end of the relay case.
> This prevented the slide from fully engaging one set of contacts. I
> replaced it and
>            that band was then okay.) After replacing the defective relay
> I lifted one end of W1 to isolate the two sections of filters and hooked
> a
>            signal  generator to the antenna connection.  I hooked my
> scope to W1 and found all low pass filter characteristics as one would
> expect,
>            no loss of signal strength on the selected band but noticeable
> attenuation on the next higher band.  I forgot to say that I had already
>            reflowed all solder connections on both the LPF and BPF
> circuits.
>
>         * I replaced C22 (2.7 pF).
>
>         * I hooked a jumper to the BPF test point (I had soldered a loop
> of wire onto D7 cathode to prevent damaging the component leads with
>            my scope probe) and could hear stations on both 20 and 30
> meters.  I coupled this lead through a capacitor (to prevent shorting 8R)
> and
>            the signals were as loud on the two bands in question as the
> other, functional bands.
>
>         * My friend Ron used a high quality capacitance / inductance
> meter and found L9 to vary from, as I recall, about 3.9~4.9 uH with the
> slug
>             top to bottom. The capacitors in circuit measured
> approximately their stamped values considering stray circuit
> capacitances.  Each of us
>             checked and rechecked the values of all components and they
> were correct.  Neither capacitors nor inductor were shorted to ground
>             except the ends of caps that were supposed to be.
>
>         * I have measured contacts 2,3,4 and 7,8,9 on relays K3 and K4
> and they function as you would expect from the relay truth table.  I even
>
>            tried a relay reset (control board removed on power up) and
> then rechecked with identical results.  I also have cheched that the
> signal line
>            (W1, W6 and BPF T.P.) is not shorted to ground on 20/30.
>
>         * When feeding a signal from my sig generator through the coax
> connector and checking at the BPF T.P. there is no noticeable attenuation
>
>             on any bands except 20 and 30 which was down about 70 dB.
>
>         * L8 peaks properly on 30 meters.  With the added cap acrross L9
> it peaks about two turns from the top of the can.
>
> At this point I had already decided to arbitrarily replace C24 and C25
> but I don't really expect any change since they check okay with a
> capacitance meter in circuit. (C19 and C20 check the same as C24 and
> C25).  I am really getting discouraged at this point, but like Little
> Orphan Annie sings, "The sun will come out tomorrow!"  Thanks to all for
> your suggestions.  If I have an epiphany, I'll let you know!
>
> 73,
>
> Pat-K4BEH
>

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