Help with K2 recieve troubleshooting

[Brian -2]

Hello everyone,

 

I am having trouble figuring out where to go next with my troubleshooting.
Here is what I have so far.  

 

I have poor receive on all bands.  The 1st thing I did was check my
soldering. Then I did the cheap and dirty signal tracing as suggested by
N0SS.  Here are my results from that.  

 

I tuned into a loud broadcast station on 7256 khz.  I was receiving 5 led
lights with the antenna plugged in normally.  (this station was 60db over s9
on my TS-2000)

Using the recommended probe I got the following:

 

1 RF Board (2 of 4), C143, input to the TUF-1 Receive Mixer.

            6 led lights

2 RF Board (2 of 4), C141, input to the Preamp. Test with the preamp ON and
OFF.

Signal levels should drop somewhat (but not disappear) when the Preamp is
OFF.

            8 led lights (preamp on)  6 led lights (preamp off)

3 RF Board (2 of 4), C53, input to the Attenuator. Test with Atten. ON and
OFF. Signal

levels should drop somewhat (but not disappear) when the Attenuator is ON.

            4 led lights (att on)  6 led lights (att off)

4 RF Board (2 of 4), D6, output of the BPF (Band-Pass Filter).

            9 led lights

5 RF Board (3 of 4), junction of C4 & C5, wiper of K1a (output 40M BPF).

            9 led lights

6 RF Board (3 of 4), junction of C7 & C8, wiper of K1b (input 40M BPF).

            9 led lights

7 RF Board (3 of 4), Jumper W6, input to BPF.

            9 led lights

8 RF Board (3 of 4), junction of D2 & D3, part of the T-R switch

            9 led lights

9 RF Board (3 of 4), junction of D3 & D4, part of the T-R switch

            Flux from 4-6 led lights

10 RF Board (3 of 4), Jumper W1, output of LPF (Low-Pass Filter)

            5 led lights

11 RF Board (3 of 4), C225, wiper of K12a, output of 40M LPF

            5 led lights

12 RF Board (3 of 4), C226 middle of 40M LPF

            3 led lights

13 RF Board (3 of 4), C227, wiper of K12b, input of 40M LPF

            5 led lights

 

I'm really stumped at this point.  Any and all help would be appreciated.  

 

 

Brian

N1WNC

K2 5946

 

 

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[Don Wilhelm-3]

Brian,

You had a good signal at the junction of D2 and D3, but it dropped
substantially at the junction of D3 and D4 (and also the remaining
places closer to the antenna).  That alone should indicate that there is
a problem with the T/R switch.

First, check the orientation of the diodes - that is most easily done by
comparing with the parts placement diagram at the back of the manual.
Of course, remove the heat sink (if it is attached) and check the
soldering carefully.

Next, refer to the RF Board DC Voltages chart at the back of the manual
and check the beginning of the leftmost column (D1 thru D7 and Q2).

If you find all the above in proper order, it *should* work (or at least
you should not still have the severe dropoff in signal between the D2/D3
junction and the D3/D4 junction).

73,
Don W3FPR

Brian wrote:

> Hello everyone,
>
>  
>
> I am having trouble figuring out where to go next with my troubleshooting.
> Here is what I have so far.  
>
> I have poor receive on all bands.  The 1st thing I did was check my
> soldering. Then I did the cheap and dirty signal tracing as suggested by
> N0SS.  Here are my results from that.  
>
> I tuned into a loud broadcast station on 7256 khz.  I was receiving 5 led
> lights with the antenna plugged in normally.  (this station was 60db over s9
> on my TS-2000)
>
> Using the recommended probe I got the following:
>

... SNIP

>
> 7 RF Board (3 of 4), Jumper W6, input to BPF.
>
>             9 led lights
>
> 8 RF Board (3 of 4), junction of D2 & D3, part of the T-R switch
>
>             9 led lights
>
> 9 RF Board (3 of 4), junction of D3 & D4, part of the T-R switch
>
>             Flux from 4-6 led lights
>
> 10 RF Board (3 of 4), Jumper W1, output of LPF (Low-Pass Filter)
>
>             5 led lights
>
> 11 RF Board (3 of 4), C225, wiper of K12a, output of 40M LPF
>
>             5 led lights
>

...
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[Brian -2]

Don,

I had some incorrect voltages on D1, D2, and D3.  I reheated the solder from
the top and that fixed my problem.  Everything looks good.  Before I
couldn't hear WWV on 10mhz. Now I'm hearing both stations at 20db over S9.
It may not be perfect yet but It's good enough for now.  

Thank you so much

Brian
N1WNC


-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Monday, April 30, 2007 8:48 PM
To: Brian
Cc: [hidden email]
Subject: Re: [Elecraft] Help with K2 recieve troubleshooting

Brian,

You had a good signal at the junction of D2 and D3, but it dropped
substantially at the junction of D3 and D4 (and also the remaining
places closer to the antenna).  That alone should indicate that there is
a problem with the T/R switch.

First, check the orientation of the diodes - that is most easily done by
comparing with the parts placement diagram at the back of the manual.
Of course, remove the heat sink (if it is attached) and check the
soldering carefully.

Next, refer to the RF Board DC Voltages chart at the back of the manual
and check the beginning of the leftmost column (D1 thru D7 and Q2).

If you find all the above in proper order, it *should* work (or at least
you should not still have the severe dropoff in signal between the D2/D3
junction and the D3/D4 junction).

73,
Don W3FPR

Brian wrote:

> Hello everyone,
>
>  
>
> I am having trouble figuring out where to go next with my troubleshooting.
> Here is what I have so far.  
>
> I have poor receive on all bands.  The 1st thing I did was check my
> soldering. Then I did the cheap and dirty signal tracing as suggested by
> N0SS.  Here are my results from that.  
>
> I tuned into a loud broadcast station on 7256 khz.  I was receiving 5 led
> lights with the antenna plugged in normally.  (this station was 60db over

s9
> on my TS-2000)
>
> Using the recommended probe I got the following:
>
... SNIP

>
> 7 RF Board (3 of 4), Jumper W6, input to BPF.
>
>             9 led lights
>
> 8 RF Board (3 of 4), junction of D2 & D3, part of the T-R switch
>
>             9 led lights
>
> 9 RF Board (3 of 4), junction of D3 & D4, part of the T-R switch
>
>             Flux from 4-6 led lights
>
> 10 RF Board (3 of 4), Jumper W1, output of LPF (Low-Pass Filter)
>
>             5 led lights
>
> 11 RF Board (3 of 4), C225, wiper of K12a, output of 40M LPF
>
>             5 led lights
>

...


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