[Amps] Question on Troubleshooting an Alpha 8410 Problem

[gudguyham at aol.com]

Hi Mike, my experience is limited with that amp but I found what might be a universal problem with that amp. There’s a separate chassis for the tube and there’s a terminal strip on the tube chassis with ring terminal wires on it so the wires can be removed easily if the tube chassis needs to be removed. There is a bunch of blue ring terminals that are crimped to all the wires that go into the tube chassis.  One wire carries considerable current and the wire is too small for a blue ring terminal, therefore the crimp isn’t sufficient.  Over time the connection becomes poor.  In the amp I fixed the wire got so hot it burned up.  I fixed it by cutting it back and soldering a smaller ring terminal.  I can see that being a universal problem.  You might want to check those wires.  Take the inspection plate off underneath and have a look.


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On Tuesday, November 29, 2022, 3:57 PM, k9mk at flash.net <k9mk at flash.net> wrote:

Greetings to the Group,

    I have been working with a friend with an Alpha 8410.  The amp has been
working well until recently when one evening the main fuses popped.  A
careful check for faults with the tubes out revealed no hard failure.  We
replaced the tubes and main fuses and amp powered right up. It worked fine
for another 3 weeks and then one night a second set of fuses popped.  This
time it occurred while operating.  Again, there was a careful search for a
hard fault, and we found nothing, and no faults were reported either.  We
replaced the fuses again and the amp is working but I expect this to be
recurring until we find the culprit.  For me this one is puzzling.  The
shack wiring is sound, weather was good, and the amp is basically treated
like a Sunday driver.  I have little experience with 4CX1500 tubes and their
failure modes. As the amp uses fast blow fuses, I thought maybe a random
electrically fast transient on the lines (truly a stretch).  Aside from that
does anyone have any thoughts on things to check or watch out for?
Intermittent soft failures like this are very frustrating....  Thanks in
advance....

73, Mike  K9MK



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