.-.-.-.-.-.-.-.-.-.-.-
...Marc,
... I have had cases were a tube arcing internally caused a big bang, but it
was elsewhere in the amp.
... The amp had rather large filter caps and a fuse in the HV circuit, and
the loud bang was usually the fuse exploding!
... HV testing the tubes is fine, but I have had 4CX250s not start acring
until their filaments had been turned on for some time. In most cases it's in a
homebrew amp were someone was running too high a voltage on the filament and
for some reason it caused one or more tubes to arc internally.
... Finally; I have experienced at least one situation where there was an arc
from the plate HV fuse to the chassis, but only at a certain frequency. That
particular problem was solved by an additional RF choke and another HV bypass
capacitor; but it was sure a tough one to troubleshoot.
... Regards,
...Dennis O.
.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
In a message dated 10/19/03 11:17:20 AM Central Daylight Time, r@somis.org
writes:
> • if the tubes arced internally, there would not have been a bang.
>
> > How could you check the tubes ?
>
> • I would check them for leakage with a high-potential tester. and I
> would also measure the resistance of each suppressor resistor by
> unsoldering one end. If a suppressor resistor is way higher in ohms,
> my guess is that the tube took off on its own.
>
> have phun, Marc
> >
> > 73
> > ON4MA Marc
>
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