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K2 meter alignment issue

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VE3WDM

K2 meter alignment issue

On page 48 of the K2 manual the S-meter alignment is done. I was able to
get the Cal S low done just fine. When I then moved on to the Cal S HI (
with the RF gain fully counter clockwise) I was not able go get any
segments of the S meter to light up. I adjusted the VFO full circle and
not one segment of the S meter would light up. The AGC voltage was
adjust to 3.80 volts DC without any problem. Also I read on the list of a
similar problem and Don suggested to check RP6 pin's 9 and 10 and U6
pin 3 (all on the control board) I reheated and soldered these, actually
all the pins on U6 and RP6 and this did not solve the problem. Just
wondering what the next step would be?MikeVE3WDM

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Don Wilhelm-4

Re: K2 meter alignment issue

Mike,

That means you have some problem with U2 or Q12. Something not
soldered? D1 not installed correctly?
Once you make those checks, if you find nothing incorrect, I can make
some voltage measurements for you.to compare.
What value did you get for the CAL S LO parameter? Something in the 175
to 190 range is normal. CAL S HI will normally be in the 18 to 25 range.

73,
Don W3FPR

On 5/30/2013 5:54 AM, Mike Weir wrote:

> On page 48 of the K2 manual the S-meter alignment is done. I was able to
> get the Cal S low done just fine. When I then moved on to the Cal S HI (
> with the RF gain fully counter clockwise) I was not able go get any
> segments of the S meter to light up. I adjusted the VFO full circle and
> not one segment of the S meter would light up. The AGC voltage was
> adjust to 3.80 volts DC without any problem. Also I read on the list of a
> similar problem and Don suggested to check RP6 pin's 9 and 10 and U6
> pin 3 (all on the control board) I reheated and soldered these, actually
> all the pins on U6 and RP6 and this did not solve the problem. Just
> wondering what the next step would be?MikeVE3WDM
>
> ______
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> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Please help support this email list: http://www.qsl.net/donate.html
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VE3WDM

Re: K2 meter alignment issue

Good evening Don, I checked the solder connections on Q12 and U2 all were good and I even reheated each connection allowing it to flow. I also checked for proper orientation for U2 and that's ok as well.
D1 is good with band facing toward Q12 and to me that is the proper direction.
As for CAL S LO the value at which the first bar goes out is 255 and comes back on at 000
As for CAL S HI I am not able to get any of the bars on the meter to light up so I do not have a value for you.
Thank very again for your time.
Mike
VE3WDM

Don Wilhelm-4

Re: K2 meter alignment issue

Mike,

That value for CAL S LO is way off. And that indicates that something
is not connected properly. Look at the schematic for the Control Board
in the lower left corner and check the values and soldering for all the
components around U2 and Q12. You also could have a problem with the
connections (including the connectors) between the Control Board and the
Front Panel RF Gain control.

I measured the voltages on a good working K2 - note that the AGC
Threshold (U2 pin 5) was set to 3.74 volts instead of 3.8 volts which
will make a little difference, but not a whole lot - the voltages should
be proportional (or set your U2 pin 5 voltage to 3.74 before measuring).

With the RF Gain control set to full clockwise:
U2 pin 5 -- 3.74 volts
U2 pin 6 -- 3.74
U2 pin 7 -- 3.73
U2 pin 8 -- 8.34 (this voltage will depend on the output of the 8 volt
regulator)
U2 pin 1 -- 3.74
U2 pin 2 -- 3.44
U2 pin 3 -- 3.42
U2 pin 4 -- 0.00

Q12 base -- 3.68
Emitter ----- 3.42
Collector -- 8.22

Then with the RF Gain set to full Counterclockwise:
U2 pin 5 -- 4.77 volts
U2 pin 6 -- 4.77
U2 pin 7 -- 4.76
U2 pin 8 -- 8.34 (this voltage will depend on the output of the 8 volt
regulator)
U2 pin 1 -- 4.30
U2 pin 2 -- 4.30
U2 pin 3 -- 4.30
U2 pin 4 -- 0.00

Q12 base -- 4.58
Emitter ----- 4.29
Collector -- 8.22

If you find the voltages for U2 pins 5, 6, and 7 do not track my
readings between full clockwise and full CCW, you can suspect a problem
in the connection between the Control board RP6 resistors and the front
panel RF Gain control.

OTOH, if the voltages for pins 5, 6, and 7 do track somewhat similar to
mine, then the RF Gain is OK and the problem is with the components
feeding U2A (pins 1, 2, and 3).

73,
Don W3FPR

On 5/30/2013 7:30 PM, VE3WDM wrote:

> Good evening Don, I checked the solder connections on Q12 and U2 all were
> good and I even reheated each connection allowing it to flow. I also checked
> for proper orientation for U2 and that's ok as well.
> D1 is good with band facing toward Q12 and to me that is the proper
> direction.
> As for CAL S LO the value at which the first bar goes out is 255 and comes
> back on at 000
> As for CAL S HI I am not able to get any of the bars on the meter to light
> up so I do not have a value for you.
> Thank very again for your time.
> Mike
> VE3WDM
>

VE3WDM

Re: K2 meter alignment issue

Good morning Don, I check the voltages on my K2 last night and here are the results.
I set my
AGC back to 3.746 from the 3.80 this way I could compare your results to mine.
With RF gain set to clockwise or full. My voltage readings are to the right of yours.

U2 pin 5 -- 3.74 volts 3.05 volts
U2 pin 6 -- 3.74 3.06
U2 pin 7 -- 3.73 3.05
U2 pin 8 -- 8.34 8.05 (note I measured 8 volt regular and it was 8.05v)

U2 pin 1 -- 3.74 2.59
U2 pin 2 -- 3.44 2.59
U2 pin 3 -- 3.42 2.58
U2 pin 4 -- 0.00 0.00

Q12 base -- 3.68 2.85
Emitter ----- 3.42 2.58
Collector -- 8.22 8.03

Then with the RF Gain set to full Counterclockwise:
U2 pin 5 -- 4.77 volts 3.74 volts
U2 pin 6 -- 4.77 3.74
U2 pin 7 -- 4.76 3.74
U2 pin 8 -- 8.34 8.04

U2 pin 1 -- 4.30 3.26
U2 pin 2 -- 4.30 3.26
U2 pin 3 -- 4.30 3.25
U2 pin 4 -- 0.00 0.00

Q12 base -- 4.58 3.53
Emitter ----- 4.29 3.53
Collector -- 8.22 8.03

These are the voltage results and I did remove the control board from the front panel board and examined P1 and J6. I have to give the connector on the front panel a look at but the knobs have to come off so I can get a good look at the board.
I hope these readings my help you out with further narrowing it down.
Thanks very much Don for spending all this time on the issue.
Mike

VE3WDM

Re: K2 meter alignment issue

Don just by way of update, I have now tried again to do the CAL S LOW and CAL S HI here are the results.
The CAL S LOW reading is now at 164
The CAL S HI reading is now at 23

Some odd things that have happened.
1. I adjusted R1 to get a voltage at U2 pin 5 of 3.80 volts. When this was done I was back to the old bad readings again. CAL S LOW of 255 and CAL S HI of nothing at all it just would not work for me I was not able to any LED bars to light when the RF gain was turned fully clockwise.
2. I then adjusted R1 so U2 pin 5 was back to 3.74 and then I tried to adjust again and still no luck
3. I then removed the boards again and looked at them as they were put back together. I did notice J8 was not seated fully. As I looked I found (looking from the back of the rig) the 2D fastener on the right side had a washer on it and it was under the control board and not allowing J8 to seat flush. I loosened the phillips screw and moved the washer forward and out from under the control board.When I put it back together all was working well again and I was able to align the S meter.
4. The last thing was after the alignment was done I came back to the radio and turned the RF gain fully counter clockwise and the S meter would not go to 10 but was flashing between 9 and 10 bars. I then went into CAL S HI and tweak it a bit from a reading of 23 to 22. All seems to be ok now.
That's where I stand at the moment Don.
Mike

Don Wilhelm-4

Re: K2 meter alignment issue

Mike,

That is good news. It sounds like the connector passing the RF Gain
lines between the control board and the RF board was the problem - high
resistance in the contact - they must be fully seated.

73,
Don W3FPR

On 6/1/2013 5:06 PM, VE3WDM wrote:

> Don just by way of update, I have now tried again to do the CAL S LOW and CAL
> S HI here are the results.
> The CAL S LOW reading is now at 164
> The CAL S HI reading is now at 23
>
> Some odd things that have happened.
> 1. I adjusted R1 to get a voltage at U2 pin 5 of 3.80 volts. When this was
> done I was back to the old bad readings again. CAL S LOW of 255 and CAL S HI
> of nothing at all it just would not work for me I was not able to any LED
> bars to light when the RF gain was turned fully clockwise.
> 2. I then adjusted R1 so U2 pin 5 was back to 3.74 and then I tried to
> adjust again and still no luck
> 3. I then removed the boards again and looked at them as they were put back
> together. I did notice J8 was not seated fully. As I looked I found (looking
> from the back of the rig) the 2D fastener on the right side had a washer on
> it and it was under the control board and not allowing J8 to seat flush. I
> loosened the phillips screw and moved the washer forward and out from under
> the control board.When I put it back together all was working well again and
> I was able to align the S meter.
> 4. The last thing was after the alignment was done I came back to the radio
> and turned the RF gain fully counter clockwise and the S meter would not go
> to 10 but was flashing between 9 and 10 bars. I then went into CAL S HI and
> tweak it a bit from a reading of 23 to 22. All seems to be ok now.
> That's where I stand at the moment Don.
> Mike
>
>
>
>
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VE3WDM

Re: K2 meter alignment issue

Don just wanted to say thanks very much for your time in assisting me getting to the bottom of the problem.
Mike