K2 VCO alignment

[nn5g]

I am on page 61 of the K2 manual on VCO alignment. All
previous tests have been OK. In connecting a DMM to
ground and R30 I get a reading of 8 volts, which is
unacceptable. I have rewound T5, replaced C72 with a
new cap and replaced L30. I have also verified that
the 6 varactor diodes are of proper values. Any ideas
out there? Thanks Paul, NN5G
_______________________________________________
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

[Don Brown-4]

Hi

This usually means the VCO is not oscillating or is way off frequency. First check with the counter probe that the 12 MHz reference oscillator is working at TP3. Then check the +5 volts on pin 16 of U4 and the 8 volt supply is ok on the input of U8. If all of that is ok then check T5 after you do that check T5 again. Make sure it is wound exactly as shown in the manual and the leads are stripped properly. Check the frequency at TP1. If you have nothing there then check the VFO ALC. With the oscillator not working the voltage on the collector of Q16 should be close to 8 volts and the drain of Q17 should be close to ground. Of course look for backward diodes, transistors, wrong value parts and missed solder joints. As a last resort suspect Q18 or Q17.

Don Brown


  ----- Original Message -----
  From: Paul Kelly<mailto:[hidden email]>
  To: [hidden email]<mailto:[hidden email]>
  Sent: Saturday, August 28, 2004 1:36 PM
  Subject: [Elecraft] K2 VCO alignment


  I am on page 61 of the K2 manual on VCO alignment. All
  previous tests have been OK. In connecting a DMM to
  ground and R30 I get a reading of 8 volts, which is
  unacceptable. I have rewound T5, replaced C72 with a
  new cap and replaced L30. I have also verified that
  the 6 varactor diodes are of proper values. Any ideas
  out there? Thanks Paul, NN5G
  _______________________________________________
  Elecraft mailing list
  Post to: [hidden email]<mailto:[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<http://mailman.qth.net/mailman/listinfo/elecraft>    
  Help: http://mailman.qth.net/subscribers.htm<http://mailman.qth.net/subscribershtm>
  Elecraft web page: http://www.elecraft.com<http://www.elecraft.com/>
_______________________________________________
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

[Don Wilhelm-2]

Paul,

8 volts on R30 usually means the VCO is not oscillating.  Try your counter
probe on TP1 to see if there is any frequency indicated - if so, check that
the frequency is correct for the band you are on (likely 40 meters at this
stage of construction) - the low band edge frequencies are listed in
Appendix B of the manual on the K2 Schematic Key sheet.

If you have no frequency indication at TP1, put the probe (carefully so not
to short adjacent pins) on U3 pin 3.  If you have a nearly correct frequency
at either of these locations, the VCO is oscillating and the trouble lies
elsewhere.

Let us know what you find.

73,
Don W3FPR

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

>I am on page 61 of the K2 manual on VCO alignment. All
> previous tests have been OK. In connecting a DMM to
> ground and R30 I get a reading of 8 volts, which is
> unacceptable. I have rewound T5, replaced C72 with a
> new cap and replaced L30. I have also verified that
> the 6 varactor diodes are of proper values. Any ideas
> out there? Thanks Paul, NN5G
>


_______________________________________________
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