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[K2] KSB2 Module Question

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Brian Handy

[K2] KSB2 Module Question

Dear Readers,

I am right now working on the KSB2 module. It's built, been installed into my K2, and I was able to hear a few stations with it. This gave me a false sense it was working, which is not actually true.

I now find that when I put the K2 into TUNE with this gizmo installed, I don't make power: set 5W on the dial, and get 0.1 indicated when I hit the TUNE button. I started going back through the DC measurements in RX mode and have turned up the following:

U2-5: 6V (should be 0.6)
U4-3: 6V (should be 0.6)

These are the ALC THR voltage, seemingly coming out of U2. I looked up the specs for U2 and I'm not quite sure what to do with this information.

What does this potentially mean?

Cheers

Brian Handy AE7JW
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Brian Handy

Re: [K2] KSB2 Module Question

To answer my own question, the problem was in T1. I didn't look at it in detail but clearly something was up; I re-wrapped it and now I'm getting all kinds of power!

Thanks to the individual who replied off-line with this hint!!

Cheers

Brian AEJ7W

________________________________
From: Brian Handy <[hidden email]>
To: "[hidden email]" <[hidden email]>
Sent: Saturday, March 16, 2013 10:27 PM
Subject: [K2] KSB2 Module Question

Dear Readers,

I am right now working on the KSB2 module. It's built, been installed into my K2, and I was able to hear a few stations with it. This gave me a false sense it was working, which is not actually true.

I now find that when I put the K2 into TUNE with this gizmo installed, I don't make power: set 5W on the dial, and get 0.1 indicated when I hit the TUNE button. I started going back through the DC measurements in RX mode and have turned up the following:

U2-5: 6V (should be 0.6)
U4-3: 6V (should be 0.6)

These are the ALC THR voltage, seemingly coming out of U2. I looked up the specs for U2 and I'm not quite sure what to do with this information.

What does this potentially mean?

Cheers

Brian Handy AE7JW
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Help: http://mailman.qth.net/mmfaq.htm
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Don Wilhelm-4

Re: [K2] KSB2 Module Question

In reply to this post by Brian Handy

Brian,

You may have had a problem with T1, but that is not in the transmit path
for a TUNE operation, so you have another problem to find if I
understood your post correctly - no power output during a TUNE operation.

TUNE uses the same path as CW, and the path for CW through the KSB2 is
short.
The BFO signal enters at P1 pin 12, goes through C42 then through diode
D3 and on to the base of Q3.
In order for that to happen, D3 must be conducting - the TXC signal
applies voltage to the cathode to forward bias D3, so be certain there
is at least 2.5 volts on the cathode.
Q3 must also conduct - again the TXC signal biases the Q3 base in
addition to D3. The 8T signal voltage flows through D5 (you should have
7+ volts on the cathode of D5 and the collector of Q3.
With those conditions present, the BFO signal should go through C39 and
exit at P1 pin 7.

The voltages I mentioned are only valid for CW transmit or a TUNE.

73,
Don W3FPR
On 3/16/2013 8:27 AM, Brian Handy wrote:

> Dear Readers,
>
> I am right now working on the KSB2 module. It's built, been installed into my K2, and I was able to hear a few stations with it. This gave me a false sense it was working, which is not actually true.
>
> I now find that when I put the K2 into TUNE with this gizmo installed, I don't make power: set 5W on the dial, and get 0.1 indicated when I hit the TUNE button. I started going back through the DC measurements in RX mode and have turned up the following:
>
> U2-5: 6V (should be 0.6)
> U4-3: 6V (should be 0.6)
>
> These are the ALC THR voltage, seemingly coming out of U2. I looked up the specs for U2 and I'm not quite sure what to do with this information.
>
> What does this potentially mean?
>
>
> Cheers
>
> Brian Handy AE7JW
> ______________________________________________________________
> 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
>

______________________________________________________________
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Brian Handy

Re: [K2] KSB2 Module Question

Don,

Thanks for the note. TUNE seems to work fine now, and I have no explanation for you why fiddling with T1 would have any effect on this. But the levels you suggest below to check are all in line, and when I plug in the dummy load I see power there. It appears, at first blush, to be working.

What isn't cooperating is ALC THR. I see 6V on U2-5 and U4-3 when I should be seeing 0.6V. Could you give me a little insight into how this part of the circuit works?

Kind regards

Brian AE7JW

________________________________
From: Don Wilhelm <[hidden email]>
To: Brian Handy <[hidden email]>
Cc: "[hidden email]" <[hidden email]>
Sent: Sunday, March 17, 2013 12:52 AM
Subject: Re: [Elecraft] [K2] KSB2 Module Question

Brian,

You may have had a problem with T1, but that is not in the transmit path
for a TUNE operation, so you have another problem to find if I
understood your post correctly - no power output during a TUNE operation.

TUNE uses the same path as CW, and the path for CW through the KSB2 is
short.
The BFO signal enters at P1 pin 12, goes through C42 then through diode
D3 and on to the base of Q3.
In order for that to happen, D3 must be conducting - the TXC signal
applies voltage to the cathode to forward bias D3, so be certain there
is at least 2.5 volts on the cathode.
Q3 must also conduct - again the TXC signal biases the Q3 base in
addition to D3. The 8T signal voltage flows through D5 (you should have
7+ volts on the cathode of D5 and the collector of Q3.
With those conditions present, the BFO signal should go through C39 and
exit at P1 pin 7.

The voltages I mentioned are only valid for CW transmit or a TUNE.

73,
Don W3FPR
On 3/16/2013 8:27 AM, Brian Handy wrote:

Don Wilhelm-4

Re: [K2] KSB2 Module Question

Brian,

In an idle (no voice) state, the ALC Threshold will start high and be
reduced as required. You 6 volt reading is OK - I just checked on a
working KSB2.

The KSB2 ALC operation is explained on page 22 of the KSB2 manual. Look
at the entire content of that page to get a view of how the ALC and
power control operate - they will compliment each other in controlling
the PEP value of the SSB signal. The values are computed in the
firmware which in turn are passed as data to the U2 DAC and then used to
control the base voltage (and therefore the conduction) of Q1.

73,
Don W3FPR

On 3/18/2013 8:27 AM, Brian Handy wrote:
> Don,
>
> Thanks for the note. TUNE seems to work fine now, and I have no explanation for you why fiddling with T1 would have any effect on this. But the levels you suggest below to check are all in line, and when I plug in the dummy load I see power there. It appears, at first blush, to be working.
>
> What isn't cooperating is ALC THR. I see 6V on U2-5 and U4-3 when I should be seeing 0.6V. Could you give me a little insight into how this part of the circuit works?
>
>

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