[Jukebox-list] Fw: Question

[Ron Rich]

Hi Mel,
Thanks for the info--got one question left (well, got all kinds of questions regarding "fuses"--but we'll leave that for later). Does the newer type construction of a "MDL" fuse qualify it for the better protection catagory?
This fuse is the "Old" Buss construction type with the spring inside.
Ron Rich


--- On Sat, 4/26/08, Mel Knight <jukeboxmel at verizon.net> wrote:

> From: Mel Knight <jukeboxmel at verizon.net>
> Subject: [Jukebox-list] Fw: Question
> To: jukebox-list at lists.netlojix.com
> Date: Saturday, April 26, 2008, 5:15 AM
> Hi Ron & David!
> 
>            I have seen this happen many times over the
> years, and it almost always was a NOS 5U4 or other
> rectifier tube that was at fault! Mostly I believe the tube
> has been vibrated a lot in someone's service truck for
> many years, or just a poor job at the factory. What I have
> found is that either the tube has some air infiltration
> allowing it to arc or some of the cathode coating has
> flaked off and is creating a bridge which creates a short
> when power is applied. Usually the air will cause the tube
> to glow really weird internally and the loose cathode
> coating will cause a cool light show, lot's of
> spitting, sparks and such! These faults almost never show
> up on a tube tester, as a rectifier tube has lots of
> voltage across the elements, and moderate current,
> especially the startup inrush. As for the fuse not blowing
> in the amp, the tube was probably shorted on one element
> and was causing a half cycle pulse, the MDL fuse takes
> several minutes to heat up and blow, as the MDL fuses that
> Seeburg and other manufacturers used were to prevent
> "needless" blowing! Needless to say, the newer
> type slo-blow types available today provide better
> protection for the transformers......   Mel
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