On May 9, 2004, at 6:46 AM, K4RO Kirk Pickering wrote:
A friend has asked me to look at his Ameritron AL-572.
The amp quit functioning about 7 months ago, after two
years of dependable service. The amplifier was used
almost exclusively on 17 meter SSB. The symptoms are
as follows:
Very low output - 100W on 20m-10m, 300W max on 160m-40m
Kirk --- Low output in 10m can be caused by a missing 10m contact in
the L-tap section of the output bandswitch.
Very high input SWR - > 3:1 on all bands, over 5:1 on 17
meters. This is the SWR the radio "sees" looking into
the input of the amplifier.
My first guess was that a component (which is common to
all bands) on the tuned input circuit has smoked. A
quick visual inspection does not reveal any burned parts.
Higher than normal input SWR with a multi-tube setup can be caused by a
tube with an open filament. I have seen this in an AL-811.
Before I go digging deeper, does anybody have any
experience with this amp or suggestions on what may
have failed? Thanks for any assistance.
-Kirk K4RO
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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