Seeing there have been several recent discussions of amps blowing fuses, I'd
like to ask for opinions on my Alpha 89. For about two years now the amp
will be trouble free for a couple of months and then while sitting idle in
standby, blow what has been every time but once the upper of the 20A fuses.
I replace the fuse and all is well for a month up to a few months and it
blows another fuse. Most of these have blown when I am out of the shack,
but occasionally I will be watching while it occurs-no pop no snap, but the
amp suddenly is off-no sign of the red fault light. The last time this
happened, I had keyed the amp with very little drive and when I did so I saw
the red fault light turn red as everything coasted to a halt. This was the
first time it had failed during transmit, and again a fuse replacement
revived it. The tubes in this amp probably have 300 hours or so on them and
deliver 2KW without complaint. It is easy to suspect a tube flashover, but
replacing a fuse every few months is a lot cheaper than replacing the tubes,
especially given their relatively low hours. I have snooped around looking
for spit marks and have found none. I have vacuumed the amp with no change.
This amp has been a little squirrelly from the day it arrived from the
factory, in contrast to an Alpha 86 which has not missed a beat other than
having the fan changed-still on the original tubes. I suppose I could swap
tubes at some point to see if the trouble follows the tubes, but I like to
keep the mitts off something which is working. If any of you have
suggestions as to possible causes or methods of tracking down such an
infrequent problem I would appreciate hearing them.
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