[Elecraft] No ALC reading

[Ron D'Eau Claire]

> I don't get any ALC reading when pressing the PTT and speaking. I find
> myself in a receiver, both on carrier alone and on audio, but no ALC
> reading. I have already tried changing R14 on SSB board to 5.6 K. Any
ideas
> before tracing every voltage?
>
> Eduardo/EA2BAJ

Eduardo, I suggest you find out whether the problem is low audio, something
wrong in the ALC circuit, something wrong in the ALC metering circuit or low
RF output. You can do this easily by turning down your POWER control and
checking the ALC and RF output on the bar graph while transmitting into a
good dummy load. As you reduce the power output, the ALC has to act more
strongly to keep the power down to your requested level.

Do this test on 40 or 20 meters. Most K2's have the greatest output on these
bands, so the ALC action is strongest there.

Connect your K2 to a good 50 ohm dummy load.

Set POWER to 5 watts.

Watch your RF output on the bar graph. It will read the "peak" RF output
when you speak into the mic.

Whistle or make a loud "Ahhhhhhh" in to the mic while transmitting and watch
your RF output on the bar graph.

If bar graph stops at about 5 watts, your ALC is working. Try turning the
POWER up to 10 watts and see if the RF output on the Bar Graph follows the
POWER setting. If so, the ALC circuit is working.

If the peak output does not reach 10 watts, make sure the transmitter can
produce the requested power when you press TUNE. If it cannot produce the RF
output you request there will be no ALC action. In that case you have low RF
gain. Try realigning the transmitter circuits.

If the ALC seems to be working, set the POWER to 5 watts and switch the
meter to ALC again. Remember that the ALC shows from right to left on the
bar graph to remind you that you are in ALC metering mode. You should see at
least one bar, and probably more when you speak in to the mic at reduced
power. If no bars show, your ALC metering circuits are at fault, although
the ALC itself is working

If you now see ALC on the bar graph at 5 watts, turn up the power and
transmit. As you increase the POWER, fewer bars will show in ALC, but you
should see at least on bar flicker on 40 or 20 meters at 10 watts. If so,
check the other bands again for ALC on the bar graph. Normally, you will see
one bar flicker occasionally on the "weakest" band where the K2 output is
lowest. This us usually 10 meters. If you don't see any ALC on a particular
band, check your RF output on the bar graph. If your bar graph is showing 10
watts in RF mode when you speak into the microphone with the POWER control
at 10 watts, your audio gain is high enough to produce full output even
though you do not see ALC on that bands.

Low audio is most likely a problem with your microphone if everything else
checks out okay as I just described. Some ops put the 1K resistor they
removed from R14 in to replace the 5.6K resistor at  R2 to increase the
audio to the Balanced Modulator to future increase the audio. But this does
not seem necessary in most K2's, and there was some concern that with a good
mic you might over-drive the Balanced Modulator.

Ron AC7AC
K2 # 1289