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k2 VCO at 12900kHz, no LSB power out

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charles_kg5cwp

k2 VCO at 12900kHz, no LSB power out

I have a k2 revB, serial #3241, that I bought off an old-timer. When I bought
it, it was "CW only". I built and installed the SSB module and discovered
that I have good power out on USB and CW, but none on LSB (at least as far
as the meter on my antenna tuner registers). I then started checking the
alignment and test and found that the VCO on 4000.1 kHz reads about 12900,
and the pot that adjusts it is already bottomed out.
I'm hoping that someone can help me identify which component is out of spec.
I removed the SSB module and re-installed C167, and here are the voltages
for control board and rf board, omitted if they're close to the value in the
table, and with an "!" annotation if they're way out.

Control Board:
U3
2 12.3
3 12.3
5 2.4
6 2.4
7 2.4
8 12.3

U4
IN 12.3

U5
IN 12.3

U6
1 5.14
9 5.11
11 5.14
18 5.15 !reversed?
19 5.13
20 5.13
24 0 !reversed?
30 5.7
32 5.1
33 5.1
37 5.1
40 5.68

U7
1 5.13
2 5.13
3 5.13
5 5.13
7 5.13
8 5.13

U8
3 5.13
6 5.13
7 5.13
8 5.13
10 5.13
11 0 !should be 5
13 5.13

U9
1 0
2 0
3 0
4 0
5 0
6 6.2
7 12.3
8 6.2

U10
6 5.14
7 5.14
14 2.3

RF Board
I didn't check the Diode or Q components yet.
U1
9 0
10 0
28 5.57

U2
IN 12.3

U3
2 4.02
3 4.02
6 4.02

U4
2 0 !
5 0 !
7 5.1 !
13 5

U5
1 5 !

U6
6 5

U8 (not sure I checked this one)

U12
1 7.7
2 7.7
5 4.75
6 2.8
8 7.8

Thanks in advance, 73's.

--
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Don Wilhelm

Re: k2 VCO at 12900kHz, no LSB power out

Charles,

12900kHz sounds like a proper frequency for the PLL Reference Oscillator
(measured at TP3). The VFO frequency is at TP1 and should be quite near
8913 kHz when tuned to 4000kHz.

Trim the corner of the KSB2 board so it clears TP1. There are no PC
traces on that corner of the board, only a ground plane on the bottom side.

As for the USB/LSB problem - what are the BFO settings for LSB and USB
for bands below 15 meters (use 40 meters)? The FL1 SSB filter must be
set to OP1. Typical BFO frequency setting for LSB should be in the
4913.6 kHz vicinity and for USB the BFO frequency should be near 4916.7 kHz.

Check those frequencies at TP2 (the test point accessible through the
hole in the KSB2 board). Go to CAL FIL in the menu, edit the parameter
(you will see the DAC value) then tap DISPLAY to see the frequency. Set
to LSB mode and you should see the LSB frequency, then go to USB mode to
read its BFO frequency.

Bottom line, I suspect your BFO frequencies are reversed or way off
where they should be.

Your voltage measurements are correct. Yes, the manual voltage listings
for the SDO and SCK signal lines are backwards from what you would read
on a DMM. The listed voltages are for the active state of those lines
which can only be observed by an oscilloscope when the VFO knob is turned.

73,
Don W3FPR

On 3/17/2019 4:00 PM, charles_kg5cwp wrote:

> I have a k2 revB, serial #3241, that I bought off an old-timer. When I bought
> it, it was "CW only". I built and installed the SSB module and discovered
> that I have good power out on USB and CW, but none on LSB (at least as far
> as the meter on my antenna tuner registers). I then started checking the
> alignment and test and found that the VCO on 4000.1 kHz reads about 12900,
> and the pot that adjusts it is already bottomed out.
> I'm hoping that someone can help me identify which component is out of spec.
> I removed the SSB module and re-installed C167, and here are the voltages
> for control board and rf board, omitted if they're close to the value in the
> table, and with an "!" annotation if they're way out.
>
> Control Board:
> U3
> 2 12.3
> 3 12.3
> 5 2.4
> 6 2.4
> 7 2.4
> 8 12.3
>
> U4
> IN 12.3
>
> U5
> IN 12.3
>
> U6
> 1 5.14
> 9 5.11
> 11 5.14
> 18 5.15 !reversed?
> 19 5.13
> 20 5.13
> 24 0 !reversed?
> 30 5.7
> 32 5.1
> 33 5.1
> 37 5.1
> 40 5.68
>
> U7
> 1 5.13
> 2 5.13
> 3 5.13
> 5 5.13
> 7 5.13
> 8 5.13
>
> U8
> 3 5.13
> 6 5.13
> 7 5.13
> 8 5.13
> 10 5.13
> 11 0 !should be 5
> 13 5.13
>
> U9
> 1 0
> 2 0
> 3 0
> 4 0
> 5 0
> 6 6.2
> 7 12.3
> 8 6.2
>
> U10
> 6 5.14
> 7 5.14
> 14 2.3
>
>
>
>
> RF Board
> I didn't check the Diode or Q components yet.
> U1
> 9 0
> 10 0
> 28 5.57
>
> U2
> IN 12.3
>
> U3
> 2 4.02
> 3 4.02
> 6 4.02
>
> U4
> 2 0 !
> 5 0 !
> 7 5.1 !
> 13 5
>
> U5
> 1 5 !
>
> U6
> 6 5
>
> U8 (not sure I checked this one)
>
> U12
> 1 7.7
> 2 7.7
> 5 4.75
> 6 2.8
> 8 7.8
>
>
>
> Thanks in advance, 73's.
>
>
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
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Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html