Ok, K2 progresses but now no audio.

[Jess Gypin]

I am testing the 40 meter receive and peaking filters at stage II testing. I
got the problem with the PLL licked and everything was working as
advertised. Now I cannot get any audio out of the radio. No hum, no hiss,
nothing with an antenna connected. I do get side tone and spot tone, so that
tells that the audio amp is working.

Where should I start?

Jess EACH


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[Don Wilhelm-3]

Jess,

Where and how you start depends on what test equipment you have available.
To begin, we need to know whether the problem is in the audio stages or in
the remainder of the receiver.

Do you have a 'scope available?  How about an audio signal generator?  Do
you have a computer with a sound card that can be used as an audio source?
Do you have an audio amplifier available with a phono or mic input
available?

You can connect an audio amplifier input to the RF board J5 location (pin 2
is ground and pins 1 and 3 are the outputs from the product detector.  If
you can hear anything through the external audio amp with that setup, the
receiver is working up through the product detector.

Injecting an audio signal into RF Board J5 pin 1 or pin 3 (ground connection
to pin 2 should produce an amplified audio signal in the headphones if the
audio stages are working. You can use a computer sound card (line out or
speaker out) as the audio source - play a CD on the computer and listen for
any output from the K2 headphones (first make certain you can hear the
computer audio through the normal computer speakers to verify that the setup
is correct).

The fact that you have sidetone only shows that the final audio amplifier IC
is capable of output, the sidetone signal is injected into that IC separate
from the receiver audio path.

What I am really saying is that we need to know which half of the receiver
is at fault here - audio stages or RF/IF, product detector stages.

73,
Don W3FPR

> -----Original Message-----
>
> I am testing the 40 meter receive and peaking filters at stage II
> testing. I
> got the problem with the PLL licked and everything was working as
> advertised. Now I cannot get any audio out of the radio. No hum, no hiss,
> nothing with an antenna connected. I do get side tone and spot
> tone, so that
> tells that the audio amp is working.
>
> Where should I start?
>
> Jess EACH
>
>

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[Matt Osborn]

Jess,

Make sure you have the jumpers installed in place of R18 & R19 on the
bottom of the control board.  These jumpers provide the path for the
output of the product detector U11 on the RF board.

If no go, check the RF board jumpers W1, W6, W5, W2 and W3  to make
sure the RF is getting to the receiver preamp, mixer, the variable
bandwidth crystal filter and then to the IF Amp and Product detector.

>From the product detector, PD1 and PD2 go through RF board J7 to P2 on
the control board. On the control board, you've got Q6 and Q7 which
disconnect the AF amp when transmitting.


On Wed, 17 Aug 2005 19:17:32 -0600, "Jess Gypin"
<[hidden email]> wrote:

>I am testing the 40 meter receive and peaking filters at stage II testing. I
>got the problem with the PLL licked and everything was working as
>advertised. Now I cannot get any audio out of the radio. No hum, no hiss,
>nothing with an antenna connected. I do get side tone and spot tone, so that
>tells that the audio amp is working.
>
>Where should I start?
>
>Jess EACH
>
>
>_______________________________________________
>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

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