Re: s/n 4276 VCO Alignment issue

[kc4wvl]

K2 s/n 4276

VCO Alignment (p61)
VFO set at 4000 kHz
L30 verified as a 4.7 uH "T005Z"

Adjusting L30 has no effect on R30 voltage reading.

*************************************************

At TP3, there is a 12100.93 kHz signal present.
At TP1, there is a 7717.86 kHz signal present.
R30 is only 0.019v
Visually inspected all components, verified that all are the correct values and no components are installed backwards. Solder joints look ok. No solder bridges or un-soldered connections found.

Changing bands does not change the reading at R30.

Visually inspected D16 and D17, both appear OK.

RFC15 is 8.5 ohms

U6-1 during PLL test, goes from 0.006v to 7.63v

U6-5 is steady at 4.004v

RFC14 leads look good and has 10 turns.

RFC15, C91 and C88 reinspected and appear ok.

T5 looks like the photo. Tried spreading and compressing the windings. No change in voltage readings at R30.

Other measurements:
U6-1 = 7.65v
U6-5 = 4.004v
U6-6 = 4.88v
U6-7 = 0.019v
U6-8 = 8.05v

U4-16 = 4.88v

Please advise.

Thank You
William Smith
KC4WVL

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[Don Wilhelm-3]

William,

That behavior is quite common if there is a solder bridge on the thermistor
board.
Check it over very carefully and I believe you will find it.

73,
Don W3FPR

> -----Original Message-----
>
> K2 s/n 4276
>
> VCO Alignment (p61)
> VFO set at 4000 kHz
> L30 verified as a 4.7 uH "T005Z"
>
> Adjusting L30 has no effect on R30 voltage reading.
>
> *************************************************
>
> At TP3, there is a 12100.93 kHz signal present.
> At TP1, there is a 7717.86 kHz signal present.
> R30 is only 0.019v
> Visually inspected all components, verified that all are the
> correct values and no components are installed backwards. Solder
> joints look ok. No solder bridges or un-soldered connections found.
>
> Changing bands does not change the reading at R30.
>
> Visually inspected D16 and D17, both appear OK.
>
> RFC15 is 8.5 ohms
>
> U6-1 during PLL test, goes from 0.006v to 7.63v
>
> U6-5 is steady at 4.004v
>
> RFC14 leads look good and has 10 turns.
>
> RFC15, C91 and C88 reinspected and appear ok.
>
> T5 looks like the photo. Tried spreading and compressing the
> windings. No change in voltage readings at R30.
>
> Other measurements:
> U6-1 = 7.65v
> U6-5 = 4.004v
> U6-6 = 4.88v
> U6-7 = 0.019v
> U6-8 = 8.05v
>
> U4-16 = 4.88v
>
> Please advise.
>
> Thank You
> William Smith
> KC4WVL
>

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