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VCO Alignment

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Steve Taylor-12

VCO Alignment

Hello All -

I ordered K2 #5329 in January, and was just able to start on it a few weeks ago. After a short break I'm back at it and this afternoon got to the Alignment and Test, Part II. All was well until I got to VCO Alignment on page 61. At first I was not able to adjust L30 and get the VCO voltage to 6.0 volts. All I could get was 7.99 volts. After reading the archives, I spread the turns on T5, and sure enough, I could get 6.0 volts at R30. But, it seems after adjusting, it drifts up slowly. So, I decided to go through the bands and see what I got. At 3500 Khz, it was a little low, and everything 7300 and above is at 7.99 volts. I've looked the board over again and again, and can't see anything wrong. Whenever I check R30 at 4000 KHz, it will be off 6.0 volts, when I adjust it back, it continues to drift, and everything above 7300 is pegged at 7.99 volts.

I hope someone has some suggestions, because I'm stumped.

Thanks in advance, Steve - WD7M
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Don Wilhelm-3

RE: VCO Alignment

Steve,

Check the number of red wire turns on T5 - count the wire as it goes
threough the center of the core - counting only the outside turns can
produce a numer that is one turn less than the proper number. This sounds
like the sitation that occurs when there is one extra turn on T5.

If you find the turns on T5 are indeed correct, the next most probable area
to be investigated is the capacitors in the VFO Range Select area.

If you have installed the rework eliminators, be very certain you follow the
instructions for the rework eliminators carefully - the capacitors for the
VFO Range select area chnge with these instructions.

73,
Don W3FPR

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

I ordered K2 #5329 in January, and was just able to start on it a few weeks
ago. After a short break I'm back at it and this afternoon got to the
Alignment and Test, Part II. All was well until I got to VCO Alignment on
page 61. At first I was not able to adjust L30 and get the VCO voltage to
6.0 volts. All I could get was 7.99 volts. After reading the archives, I
spread the turns on T5, and sure enough, I could get 6.0 volts at R30. But,
it seems after adjusting, it drifts up slowly. So, I decided to go through
the bands and see what I got. At 3500 Khz, it was a little low, and
everything 7300 and above is at 7.99 volts. I've looked the board over
again and again, and can't see anything wrong. Whenever I check R30 at 4000
KHz, it will be off 6.0 volts, when I adjust it back, it continues to drift,
and everything above 7300 is pegged at 7.99 volts.

I hope someone has some suggestions, because I'm stumped.

Thanks in advance, Steve - WD7M

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Steve Taylor-12

Re: VCO Alignment

Don -

Thanks for the reply. I checked as you suggested, T5 turns are okay, I
looked the capacitors over good and resoldered all, okay. I do have the
rework eliminators installed, and I looked them over good, seems okay. No
real change. The strange thing is, when I first power up with the VFO set
at 4000, I measure about 5.3 volts at R30 and it slowly drifts up. After 5
or so minutes it's at 6.3 volts and still climbing. I think the work I did
before that I thought allowed me to adjust L30 really was a matter of me
powering down to spread the windings on T5 and then powering back up. It's
a clue, but I don't know what it means.

Steve - WD7M

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Steve Taylor" <[hidden email]>; <[hidden email]>
Sent: Thursday, May 18, 2006 7:13 PM
Subject: RE: [Elecraft] VCO Alignment

> Steve,
>
> Check the number of red wire turns on T5 - count the wire as it goes
> threough the center of the core - counting only the outside turns can
> produce a numer that is one turn less than the proper number. This sounds
> like the sitation that occurs when there is one extra turn on T5.
>
> If you find the turns on T5 are indeed correct, the next most probable
> area
> to be investigated is the capacitors in the VFO Range Select area.
>
> If you have installed the rework eliminators, be very certain you follow
> the
> instructions for the rework eliminators carefully - the capacitors for the
> VFO Range select area chnge with these instructions.
>
> 73,
> Don W3FPR
>
> -----Original Message-----
>
> I ordered K2 #5329 in January, and was just able to start on it a few
> weeks
> ago. After a short break I'm back at it and this afternoon got to the
> Alignment and Test, Part II. All was well until I got to VCO Alignment on
> page 61. At first I was not able to adjust L30 and get the VCO voltage to
> 6.0 volts. All I could get was 7.99 volts. After reading the archives, I
> spread the turns on T5, and sure enough, I could get 6.0 volts at R30.
> But,
> it seems after adjusting, it drifts up slowly. So, I decided to go
> through
> the bands and see what I got. At 3500 Khz, it was a little low, and
> everything 7300 and above is at 7.99 volts. I've looked the board over
> again and again, and can't see anything wrong. Whenever I check R30 at
> 4000
> KHz, it will be off 6.0 volts, when I adjust it back, it continues to
> drift,
> and everything above 7300 is pegged at 7.99 volts.
>
> I hope someone has some suggestions, because I'm stumped.
>
> Thanks in advance, Steve - WD7M
>
> --
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.1.392 / Virus Database: 268.5.6/339 - Release Date: 5/14/2006
>
>

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Don Wilhelm-3

RE: VCO Alignment

Steve,

I cannot comment a lot about the drift much at this time, but if you have
the rework elminators installed (including the change in capacitors and the
installation of D19 and D20), be certain you have the K2 menu item for D19
set to YES - that should allow you to get all vco voltages within range. (I
ask again for the rework eliminator guys to remove this part of their
instructions - it really complicates the VCO range stuff by changing these
components - and there is no way to properly test it for proper ranges
because you still cannot tune to the critical point at 5300 Hz until you
fully install the K60XV)

On the drift, I would have to ask about the 120 pf cap that you used to
replace the 82 pf cap - is it drifting with temperature changes? What is
its quality? specs? Or might there be some other cause? The same questions
apply to the varactors you installed in the D19 and D20 locations.
Everything is suspect in this area until we know exactly what you have in
these locations. It may just be a case of the VCO/PLL trying to adjust
things, but I have never observed a drift in this measurement - just try to
get all bands within range as a first attempt and then look at any remaining
drift in the VCO as a secondary consideration.

If you continue to have problems, please back out this portion of the
'rework eliminator' changes (remove D19 and D20 and change C71 back to 82
pf) so you can properly test the base K2 function for VCO range.

73,
Don W3FPR

-----Original Message-----
From: Steve Taylor [mailto:[hidden email]]
Sent: Thursday, May 18, 2006 11:13 PM
To: [hidden email]; [hidden email]
Subject: Re: [Elecraft] VCO Alignment

Don -

Thanks for the reply. I checked as you suggested, T5 turns are okay, I
looked the capacitors over good and resoldered all, okay. I do have the
rework eliminators installed, and I looked them over good, seems okay. No
real change. The strange thing is, when I first power up with the VFO set
at 4000, I measure about 5.3 volts at R30 and it slowly drifts up. After 5
or so minutes it's at 6.3 volts and still climbing. I think the work I did
before that I thought allowed me to adjust L30 really was a matter of me
powering down to spread the windings on T5 and then powering back up. It's
a clue, but I don't know what it means.

Steve - WD7M

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Steve Taylor" <[hidden email]>; <[hidden email]>
Sent: Thursday, May 18, 2006 7:13 PM
Subject: RE: [Elecraft] VCO Alignment

--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.392 / Virus Database: 268.5.6/339 - Release Date: 5/14/2006

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.392 / Virus Database: 268.5.6/339 - Release Date: 5/14/2006

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