[Elecraft] no audio output: K1

Wed Jan 14 10:21:01 2004

Steve,

I just thought I'd make sure that that you had the jumper on the filter
board installed, as you subsequently verified.

The simple way that I trace for an audio signal is to connect one lead of a
capacitor (value not critical, but above 0.1 uF or so) to the tip of an
earphone's jack, and the shaft of the jack to ground on the K1.  Then I
stick the unconnected lead of the capacitor to whatever PCB point I want to
check while listening for noise in the phones.  Tracing backward, in the K1
receive (non-muted) mode there should be low level audio detected at RF
board connector P1 pin 2, Q11 drain, U3 pin 5, and U3 between pin 2 and pin
3 (remove the phone's ground lead from ground and connect the phone across
pin 2 and 3).

Loss of audio could be due to defective U3 (not likely), shorted muting
transistor (source to drain) Q10 (possible due to the delicate nature of
MOSFETs), open muting transistor (source to drain) Q11, along with various
other signal loss paths.

If you got desparate, you could lift the source or drain of Q10 and see if
audio returns, but remember that this transistor can be easily damaged in
the process if it isn't already.

The fact that you hear the MCU-generated sidetone shows that U4 and
downstream is probably OK.

Usually audio problems are pretty easy to find and solve, but your's will be
complicated by the fact that the filter board hasn't been aligned yet so
there's not going to be a whole lot of audio noise to detect.

Good luck,
Mike / KK5F

-----Original Message-----
From: Steven J Baumrucker, MD <[email protected]>
To: Mike Morrow <[email protected]>
Date: Wednesday, January 14, 2004 8:38 AM
Subject: RE: [Elecraft] no audio output: K1

>not a hint of noise!
>
>the jumper is in place (I thought of that, too!) I think it's audio,
>unfortunately!
>
>
>steve
>
>
>
>> -----Original Message-----
>> From: Mike Morrow [mailto:[email protected]]
>> Sent: Wednesday, January 14, 2004 9:27 AM
>> To: [email protected]
>> Subject: Re: [Elecraft] no audio output: K1
>>
>>
>> Steve,
>>
>> Do you not get even a hint of noise?  If you did, I'd ask if
>> you've got the
>> jumper installed on the filter board connector that has to be in
>> place until
>> the KAT1 is installed.
>>
>> 73,
>> Mike / KK5F
>>
>> -----Original Message-----
>> From: Steven J Baumrucker, MD <[email protected]>
>> To: [email protected] <[email protected]>
>> Date: Wednesday, January 14, 2004 8:27 AM
>> Subject: [Elecraft] no audio output: K1
>>
>>
>> >I'm in the testing and alignment phase prior to constructing the
>> transmitter
>> >section.  All has checked out perfectly until time to get some noise out
>> for
>> >the 4 band filter board alignment.  I get no audio out at all.
>> >
>> >1) sidetone generator puts out sound so U4 must be working
>> >2) all voltages for U3 are correct
>> >3) I can't see any missing components
>> >
>> >
>> >I suspect I have a component failure somewhere...Q10 or Q11 perhaps?
The
>> >manual states to "trace the audio chain" or something similar and
frankly
>> >I'm too dumb to figure this out!
>> >
>> >thanks for any help!  I'm getting desperate! :-)
>> >
>> >73!
>> >
>> >
>> >--Steve
>> >
>> >_______________________________________________
>> >Elecraft mailing list: [email protected]
>> >You must be subscribed to post to the list.
>> >To subscribe or unsubscribe see:
>> http://mailman.qth.net/mailman/listinfo/elecraft
>> >Elecraft Web Page: http://www.elecraft.com
>> >Also see: http://www.elecraft.com/elecraft_list_guidelines.htm
>>
>