>
>This subject has probably be covered before but I thought
>that I would again share this with the group.
>
>The Radio Club here at Diego Garcia has two AL-80B
>Ameritron amps. A month ago we had a 3-500Z short and
>it had to be replaced.
Have any operators heard spitting sounds coming from the bandswitch?
What is the measured resistance of the suppressor R.? // Bandswitch
damage frequently occurs at the 160m and 80m Tune-C padder contacts.
(see AL-80 & SB-1000 bandswitch photos on my Web site) // With nothing
to act as a grid fuse, and no glitch resistor, there is no grid
protection in the AL-80. These design oversights are easily fixed.
However, for those with a free supply of tubes, ... ... ...
>Last night the other amp's 3-500Z
>shorted and we also had to replace that one. While checking the
>schematic during this process, we noticed that the
>OPR/STANDBY switch only enables the keying relay.
>The High Voltage comes on and remains on with the
>OFF/ON switch. We were all a bit shocked by this design
>and wanted to warn others before they are fatally shocked
>by this design!
>
This is normal for communications-duty linear amplifiers. Switching off
the HV supply does not make an amplifier safe. 120vac is potentially
more lethal than several kV. . To see the next sunset, always pull the
mains plug before putting one's hands in a linear amp.
>
later, Joe
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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