KPA100 First tests (p 22)

classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

KPA100 First tests (p 22)

MARY HAYS CARNEY
Time to add some extra kick to my K2-10; but, of course, problems arise along the way:
 
I find that U1 pin 2 to ground is only 5 kohms rather than > 10K.  I can find no  solder bridges or misplaced components.
  Resistors R24 and RP1 show the correct values.  Should I suspect that Q10 is shorted?  Other pins on U1 give correct resistances.
 
U4, pin 8 shows a resistance of only about 2.8K rather than the expected >10K.  (As directed, the +ve lead of the meter is on pin 8, -ve lead to ground.)  The circuit diagram suggests that this is to be expected since the measurement is made through two forward-biased diodes (D7 and D8) to ground.  Reversing the meter leads gives the expected high value of resistance.
 
Voltage tests as indicated on p 26 of the manual give expected voltages with only 300 ma total current (20 ma increase over the K2 alone).
 
Joe Carney, KB3FBR
     
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: KPA100 First tests (p 22)

Don Wilhelm-4
Joe,

It is entirely possible that your ohmmeter is using polarity that is
different than normal for DMMs.
You *are* using a DMM are you not?  If you are using a VOM or VTVM, stop
- the voltage used in those meters (ohmmeter function) may be high
enough to saturate semiconductor junctions and possibly cause damage.

If you do have a DMM, try the U1 pin 2 resistance with reversed leads.

73,
Don W3FPR

On 1/23/2014 11:23 AM, MARY HAYS CARNEY wrote:

> Time to add some extra kick to my K2-10; but, of course, problems arise along the way:
>  
> I find that U1 pin 2 to ground is only 5 kohms rather than > 10K.  I can find no  solder bridges or misplaced components.
>    Resistors R24 and RP1 show the correct values.  Should I suspect that Q10 is shorted?  Other pins on U1 give correct resistances.
>  
> U4, pin 8 shows a resistance of only about 2.8K rather than the expected >10K.  (As directed, the +ve lead of the meter is on pin 8, -ve lead to ground.)  The circuit diagram suggests that this is to be expected since the measurement is made through two forward-biased diodes (D7 and D8) to ground.  Reversing the meter leads gives the expected high value of resistance.
>  
> Voltage tests as indicated on p 26 of the manual give expected voltages with only 300 ma total current (20 ma increase over the K2 alone).
>  
> Joe Carney, KB3FBR
>    
> ______________________________________________________________
> 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
>

______________________________________________________________
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