This past weekend my AL 80-A (1 3-500z) quietly ceased to function
properly. I was attempting to contact the 3C5DX on 20m and
driving the amp at around 400w output when suddenly there
was no longer any indication of either grid or plate
current. The meters were still on and the HV would still
indicate around 3200v but the tube was completely dark.
I use this amp very sparingly (keeps the neighbors quiet) and
never at full output. Since I purchased it used a couple of
years ago, I have no idea how old the tube is but until this
past weekend, I have had no problems with the amp. The serial
number of the amp is 0768 so I would guess it's pretty old.
What two pins on the tube are the filament and if a defective
filament is not the problem, what should I check next?
Thanks in advance for your help,
Wayne AJ5M ehayes@vnet.ibm.com
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