K2 - S-Meter alignment/Bargraph segements

[Löbel]

Dear OM's,

 

thank you for reading this.

 

Yesterday I finished the control board, the front panel board and

the first stage of the RF-board - ready for the alignment, part 1.

 

Yesterday I did all the steps from the manual, alignment part 1

sucessfully - even the S-Meter alignment and the bargraph current test.

 

Today I switched on the K2 again and the bargraphsegment number 2 was

lighting. So I decided to do the S-Meter alignemnt again.

 

And so the mistery began. First with "CAL S LO" by turning the VFO-knob

the bargraph segments hop from nr. 10 to nr. 7 and then to nr. 3 ....

Similiar behavior with "CAL S HI".

 

I did the "GRPH BAR" - Test and only saw the first 3 segments on.

Then I tried again the S-Meter alignement but no segement visible any
more....

So back to the "GRPH BAR" - now not one segment is on....

 

I have to mention, that I didn't changed anything from yesterday

to today an the R1 was adjusted to 3,8 Volt as shown in the manual.

 

Has my K2 destroyed himself or what could be the reason for that

bad behavior? All other things in the alignment part 1 still are ok.

The RF-Gain control does not change anything.

 

I am really thankful for every help.

 

73 de Guenther / OE2LCM

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[Don Wilhelm-4]

  Geunther,

The most likely cause of bargraph LEDs not lighting is an intermittent
soldering connection, and since some LEDs light while others do not, the
problem is most likely found on the Front Panel board.
I would suggest you re-flow the soldering of Front Panel U4, RP2, R12,
and the bargraph itself.  Use a hot soldering iron and add a little new
solder to add a bit of new flux.

Examine your soldering critically, it should flow out to an almost
invisible edge line on both the solder pad and the component lead.  Only
enough solder to fill the thru-plated hole is required, but I like to
see a small fillet of solder too.  If there is just a lump of solder,
you have applied excess (which can hide a bad connection), use solder
wick or a de-soldering tool to remove the excess and re-solder with only
a minimum of additional solder.

If you are trying to use lead-free solder, be aware that it does not
flow very well and requires a higher than normal soldering temperature.  
I would recommend that you use a 63/37 alloy lead-tin solder with a
mildly reactive flux instead of trying to struggle with the lead-free
solder.  Even with much practice, I have not been able to make any
lead-free solder flow well.  There is a reason that lead-free solder is
not to be used for avionics or space gear!

73,
Don W3FPR

On 2/13/2011 8:54 AM, Löbel wrote:

> Dear OM's,
> thank you for reading this.
>
> Yesterday I finished the control board, the front panel board and
> the first stage of the RF-board - ready for the alignment, part 1.
> Yesterday I did all the steps from the manual, alignment part 1
> sucessfully - even the S-Meter alignment and the bargraph current test.
>
> Today I switched on the K2 again and the bargraphsegment number 2 was
> lighting. So I decided to do the S-Meter alignemnt again.
> And so the mistery began. First with "CAL S LO" by turning the VFO-knob
> the bargraph segments hop from nr. 10 to nr. 7 and then to nr. 3 ....
> Similiar behavior with "CAL S HI".
>
> I did the "GRPH BAR" - Test and only saw the first 3 segments on.
> Then I tried again the S-Meter alignement but no segement visible any
> more....
> So back to the "GRPH BAR" - now not one segment is on....
>
> I have to mention, that I didn't changed anything from yesterday
> to today an the R1 was adjusted to 3,8 Volt as shown in the manual.
>
> Has my K2 destroyed himself or what could be the reason for that
> bad behavior? All other things in the alignment part 1 still are ok.
>
> The RF-Gain control does not change anything.
>

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
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Please help support this email list: http://www.qsl.net/donate.html