I discovered that if you turn the potentiometer R20 in the frequency
counter portion of the Input T/R PWB (Assy ABX-X182) fully clockwise,
it disables the frequency counter and auto band-switching that goes with
it. Assuming the proper load and tune capacitor settings are stored for
each band and segment, manual band-switching works perfectly and will
get me by for now.
73, Mike W4EF................................
On 3/2/2026 3:30 AM, Michael Tope wrote:
One of my Alpha 87A has a problem with the frequency counter that is
used by the amplifier to automatically switch bands based on the
frequency of the input signal. Normally this is a desirable feature,
however, my amp has this problem whereby it will work fine for a
while, then the frequency counter will start to malfunction. The
counter appears to produce erroneous readings whereby it thinks its on
a different frequency than it actually is. This causes the unit will
try to re-tune right in the middle of a transmission. Eventually it
gets so bad that it renders the amp unusable.
Does anyone know if there is an easy way to turn-off or the disable
the frequency counter in such a way that the amplifier won't be able
to recognize the frequency of the input signal, but it will otherwise
operate normally (with the exception that you would have to select the
band manually). I tried doing this with remote control software, but
that didn't work. I think that just turns off the auto-tuning whereby
it defaults to the stored tuning parameters for the band determined by
the frequency counter instead of following the AlphaMax auto-tuning
algorithm. Eventually I'll want a proper fix for this problem, but I
need to use the amplifier in the short-term, so I need a band-aid that
won't involve hours of troubleshooting.
73, Mike W4EF................
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