On May 6, 6:57 pm, Chief_Bi...@[EMAIL PROTECTED]
wrote:
> I've NEVER had to replace an input AC fuse on a piece of stereo gear,
> but my old Kenwood KA-9X amp blew one the other day. It's a Toyo 6A
> fuse (thats ALL it says on it..both ends: Toyo 6A) , and I suppose a
> 250VAC/6A fuse would work except I can't tell if it was a slo-blow or
> fast blow cause there isn't much left. I'm surmising its a slo-blow,
> but can anyone tell me what type is typically used for the input fuse
> on solid state integrated stereo amps.
Slow Blow fuses will leave the ceramic rod inside the holder.
Dual-Element fuses will leave the small spring and clip inside the
holder.
Standard & Fast-Blow fuses will leave little or nothing remaining
inside the holder.
6A seems mighty close for a 700-watt @[EMAIL PROTECTED]
120V (5.8A) integrated
amplifier. What does it say on the fuse-holder? Mostly these things
typically use a dual-element or slow-blow as well. IF the fuse blew
because it is a 6A standard fuse, go ahead and replace it with a dual-
element and see what gives. If it blew for some other reason -beware.
But, before you willy-nilly replace the fuse and go back to sleep, you
need to do several things:
a) determine to the degree possible _why_ the fuse blew. Anything
unusual happen? You may just be very lucky that a 6A standard fuse
held for so long anyway.
b) determine what the correct fuse should be. Look up a manual or
service literature or look at the fuse-holder for information. Note
that a fuse at 120V will carry twice the amperage rating than a fuse
at 240V for the same unit - not knowing where in the world you might
be. So, 6A at 240V is "too many". 6A at 120V is "barely enough" if a
standard type.
c) if you cannot do this, determine the actual current required by the
amplifier. You can do this to a degree by connecting it to a sensitive
ammeter and running it hard, or you can intuit from the nameplate
rating (in watts) to a reasonable degree. 700/120 = 5.83A, use 6A
(Dual-Element).
Note that the turn-on surge may be up to 3X the steady-state
requirement - and perhaps why it is that 6A fuse blew - all the
previous owner had was a standard fuse, and 6A was large enough to
handle the turn-on surge for a while.
Dual-Element fuses: Why do I harp? A DE Fuse acts like a slow-blow at
turn-on, handling the surge, but acts as a standard fuse after the
initial surge. So you get maximum protection of the equipment with
little risk of overloading. Note that a Slow-Blow fuse operates on a
function of overload/time. A small overload will be tolerated for a
very long time, a large overload for a much shorter time. That small
overload may be tolerated long enough to cause "other" parts to fail.
A dual-element fuse will tolerate a large load for a brief period, but
then fails at the set-point. Slow-Blow fuses (wire wound around a
ceramic core) protect nothing well.
Peter Wieck
Melrose Park, PA
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