[R-390] Blown B+ Fuse - Cont'd

[Barry]

Fuses are new.

I put the remaining fuse inline with the amp meters.  Circuit drew anywhere
from 70 to 100mA and the fuse held.  Perhaps a bad fuse, perhaps a bad tube.
Dunno.  I thumped all the tubes (except the 26Z5W's) with my finger and
didn't notice any sudden jumps in current.  I'm still figuring something is
lurking, but if I can't get the fuse to blow, then I suppose I can let it
alone.

Thanks guys!

Barry - N4BUQ

>
> Lee wrote:
>
> > Fuses wear out and blow for that reason besides protecting a circuit.
> > Surges and vibration also take their toll on a fuse besides just the
every
> > day daily current flow throught the fuse.
>
>
> Barry mentioned that he had just put in the correct fuse (1/8 instead of
1/4
> amp), though slow blow rather than the F/B that's supposed to be used.
>
> In addition to wear and tear, defective fuses aren't unheard of.  If
NOS --
> really old -- there could be some deterioration on the shelf, depending on
> storage conditions.  Fuses aren't sealed.  I've seen some where the glue
had
> given out and just installing them causes one or both end caps to twist --
> also some that looked corroded inside or had an awful lot of rosin showing
> in the end-caps where the wires are soldered.  I suspect a bit of
corrosion
> or a slight twist can affect the actual current "tolerance".  And there
can
> be some that were just made wrong/defective.  I'd check another one with
> just one of the meters in series, since they read the same when the
current
> was measured before.  May as well put in another order for 1/8th amp
> fuses -- fast blows -- from another source.
>
> Barry
>
>
>
>