Elecraft

TP2

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Peter-64

TP2

Hi

I have a K2 rig here for repair and this baby has a instable frequentie reading on TP2
Afther touching a part of the bfo its solid (4,917 mc)
Q24 is working good, but on U11 (bfo) pin 6 and 7 are 1 volt too low.
I a have all ready replace D37 and D38 bun no effect.

Question. Why are there 2 cristals? (X3 and X4)
The low voltage on pin6 and 7 of U11 is this caused by a defect IC or something else?

Peter
PC2A

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Peter-64

Re: TP2

Some ask for more info.

With the probe in TP2 and CALL on FCTR the reading jumps fast around 4.620 mc
Then the voltage on RP6 is stable reading 6,48V

Pressing BAND -
The readout is 4,917 mc and stable but the voltage on RP6 has jumped to 8,0V

>
> I have a K2 rig here for repair and this baby has a instable frequentie reading on TP2
> After touching a part of the bfo its solid (4,917 mc)
> Q24 is working good, but on U11 (bfo) pin 6 and 7 are 1 volt too low.
> I a have all ready replace D37 and D38 bun no effect.
>
> Question. Why are there 2 cristals? (X3 and X4)
> The low voltage on pin6 and 7 of U11 is this caused by a defect IC or something else?
>
> Peter
> PC2A
>

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Don Wilhelm-3

Re: TP2

Peter,

My guess is that there is a bad solder connection somewhere in the BFO area.
The fact that things stabilize when you touch something in the area strongly
suggests something wrong with the soldering.

Pressing BAND+, BAND- when in CAL FCTR should swing the voltage between 0
and 8 volts, so it seems things are likely OK with the control voltage.

The only other thing I can think of which would cause similar behavior is a
weak crystal. If you suspect the crystals, try removing one of them and see
if the behavior stabilizes (the BFO range will become more narrow - so that
is only for a test, not a cure). 2 parallel crystals are used to 'de-Q' the
crystals and provide a greater BFO range than one alone would provide.

73,
Don W3FPR

----- Original Message -----

> Some ask for more info.
>
> With the probe in TP2 and CALL on FCTR the reading jumps fast around 4.620
> mc
> Then the voltage on RP6 is stable reading 6,48V
>
> Pressing BAND -
> The readout is 4,917 mc and stable but the voltage on RP6 has jumped to
> 8,0V
>
>>
>> I have a K2 rig here for repair and this baby has a instable frequentie
>> reading on TP2
>> After touching a part of the bfo its solid (4,917 mc)
>> Q24 is working good, but on U11 (bfo) pin 6 and 7 are 1 volt too low.
>> I a have all ready replace D37 and D38 bun no effect.
>>
>> Question. Why are there 2 cristals? (X3 and X4)
>> The low voltage on pin6 and 7 of U11 is this caused by a defect IC or
>> something else?
>>
>> Peter
>> PC2A
>>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

Peter-64

Re: TP2

>

Don and all

I did carefully removed L33 and both crystals. Replace L33 but with room to solder both
crystals on the solder side. When solder 1 crystal at the time they both give the wanted
reading and they are stable. But when both are solderd its jumping around.

>
>
> My guess is that there is a bad solder connection somewhere in the BFO area.
> The fact that things stabilize when you touch something in the area strongly
> suggests something wrong with the soldering.
>
> Pressing BAND+, BAND- when in CAL FCTR should swing the voltage between 0
> and 8 volts, so it seems things are likely OK with the control voltage.
>
> The only other thing I can think of which would cause similar behavior is a
> weak crystal. If you suspect the crystals, try removing one of them and see
> if the behavior stabilizes (the BFO range will become more narrow - so that
> is only for a test, not a cure). 2 parallel crystals are used to 'de-Q' the
> crystals and provide a greater BFO range than one alone would provide.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>
> > Some ask for more info.
> >
> > With the probe in TP2 and CALL on FCTR the reading jumps fast around 4.620
> > mc
> > Then the voltage on RP6 is stable reading 6,48V
> >
> > Pressing BAND -
> > The readout is 4,917 mc and stable but the voltage on RP6 has jumped to
> > 8,0V
> >
> >>
> >> I have a K2 rig here for repair and this baby has a instable frequentie
> >> reading on TP2
> >> After touching a part of the bfo its solid (4,917 mc)
> >> Q24 is working good, but on U11 (bfo) pin 6 and 7 are 1 volt too low.
> >> I a have all ready replace D37 and D38 bun no effect.
> >>
> >> Question. Why are there 2 cristals? (X3 and X4)
> >> The low voltage on pin6 and 7 of U11 is this caused by a defect IC or
> >> something else?
> >>
> >> Peter
> >> PC2A
> >>
> >
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> >