[MFJ-Ameritron] Help With Amp Issue

[Duane Fischer, W8DBF]

Hello All,

W8DBF, Duane from Flint, MI. I am totally blind and live alone.

Several days ago my Ameritron AL-82a did something that may indicate a
problem. I need your wisdom and experience, please.

The amp is 18 months old and has never been mistreated or overdriven. I use
only 35 watts of drive. It was tuned using 45 watts and then I turned the
drive down. It is used only on 20 meters USB.

The SWR on all antennas is less than 1.5 on all antennas 'without a tuner'.

I warmed the amp up, then did an on air check on 14.315 MHZ. All was as it
should be. I then sat and waited for some Ham friends to arrive.

I heard a loud "SNAP!", while sitting there listening. I immediately put the
amp on "standby" while I checked around.

I found nothing amiss or different.

Then the amp made another "SNAP", which I believe is a high voltage arc. The
amp was still in the "standby" mode.

I thought it might be the reclining/swivel heavily padded Ham Shack chair
making the sound, so I got out of it. I moved the chair several times and
heard the sound. Just to be sure, I shut the amplifier totally off.

I could not reproduce the "snap" with the chair.

I remained standing and switched the amp back on. At about the one minute
point in the three minute warmup cycle I heard the "SNAP". I had my finger
on the power switch, so I powered her down.

I never change the position of the band switch, as it is tuned for 20 meters
and that is where I use it.

I also never move the load and tune knobs. It is tuned for the midpoint of
the band +/-75. Since it is always used on 20 meters, no reason to retune.
Provided I do not accidentally move one of the knobs, of course.

I am being told two things.

1. The fact that I never move the band select, plate or tune knobs may be
allowing dust particles to get between the plates and arc.
I have had this happen once in a great while, maybe three times in eleven
years. However, this did not arc once, but about a dozen times, total.

2. That sometimes the finals have some kind of 'something' inside them that
they simply burn off and that is the arc I am hearing. Nothing to worry
about. Keep using it.

There has been no other noise from the amp, such as capacitor blowing. There
has been no odd smell from it. No burned odor. Nothing else unusual.

When I did the on air check, the amp was showing 3600 HV, before I keyed it,
of course. The amp was delivering the output it is tuned to produce.

One amp expert told me under the conditions described, not to worry. This
sometimes just happens and will correct itself. He told me to just use it.
The blocking resistor would absord the arcs and prevent any damage to the
pair of 3-500 finals. If there was a problem, the amp would shutdown and I
would know something was wrong.

So, gentlemen, what should I do?

Thank you.


Duane Fischer, W8DBF - WPE8CXO
E-Mail: dfischer at usol.com
Hallicrafters web site: www.w9wze.net
HHRP web site: hhrp.w9wze.net