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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