[Elecraft] K2 audio output low after upgrades

[Don Wilhelm]

Iain,

I suspect it is not really an audio problem, but a problem somewhere in 
the receiver front end or IF or product detector.  If the S-meter is 
less lively than before, the problem is prior to the Product Detector, 
but if the S-meter has the usual response, look at the product detector 
and audio amp connections.  Was the KAF2 plugged into the headers one 
pin too high - that leaves only half of the audio path operative.

I would suspect the K60XV above all the other options.  Pull it out of 
the socket and jumper J13 between pins 3 and 5 with a short wire.  If 
the receive comes alive (it is not expected to work on 40 meters), then 
the K60XV is the problem spot.
It is easy to remove the KAT2 for a test, just pull the cables out and 
connect the antenna to the base K2..
If the other options were removed, make certain they are plugged in 
correctly and not one pin off.
You can bypass the KSB2 for receive (not transmit) with a wire jumper 
plugged between pins 1 and 3 of J9 and J10.
The K160RX can be bypassed by putting a wire jumper between pins 1 and 7 
of J14.

If all those things check out OK, then look for something that was 
inadvertently moved during the addition of the new options.

73,
Don W3FPR

On 8/31/2013 11:34 AM, Iain Kelly M0PCB wrote:
> Greetings list,
>
> I've been assisting my partner Chloe M0GEJ with some upgrades to her 
> K2 (s/n 5484) and we've come a bit unstuck.
>
> It's  a base K2 with SSB, 160m and the KAF2. She has added the 
> internal ATU and the 60M module. She also had to replace a faulty 
> headphone jack on the front panel as it had gone u/s. When 
> re-assembled we noticed the audio output level is significantly down 
> on what it was before.
>
> The CW side-tone level is unaffected. Both the speaker and phone jack 
> are affected. The audio level at maximum volume setting is just below 
> normal levels required in headphonesand not very loud for internal 
> speaker use.
>
> What we have tried:
>
>  - Full receive and transmit alignment: signals are received well and 
> showing good strength on the s-meter, both off-air and from my signal 
> generator.
>  - RF Gain set to Max
>  - Checked RANT selection
>  - Checked R1 (AGC Threshold setting)
>  - Measured the 5V and 8V lines
>  - Replaced U9 (LM380N-08) on the main board in case the old damaged 
> headphone jack had caused damage.
>