writes:

Walt wrote:
wrote:

Let me guess: It sounds much more warm without the fuse. LOL.

No, I wouldn't describe it as that. Without going into minute details,
the overall resolution is much higher.

Question is: Exactly what risks are there in running an integrated amp
or a preamp sans fuse?

You could burn up the power supply, or it could catch on fire. Put the
damn fuse back in.

Could you describe just what condtions would cause the power supply to
burn up or catch on fire (I would not have thought this component to be
flammable!)?

Let's think your amplifier has a transformer that is designed togive out
100W output power at 90% effeciency. So when amplifier takes 100W,
then tranformer has 10W loss and this is what gets it somewhat warm
(transformer takes somwehat less power loss when it not fully loaded).
If the transformer secondary gots shorted (insulation on transformer
secondary wires fails and thei copper ouches each other, amplifier
brige rectifier fails short, transformer main storage capacitor fails
short or amplifier main output transformer fail fully short...).
In this case the transformer secondary is practically short circuited,
and transformer tries to push as much power as it can to the output...
taking this power from the input. Typically you can expect this
input power become something like 10 times the nominal power power
of the transformer (or somewhat more or less depending on transformer
design, but 10 times is a quite good approximation for average transformer).
No actual power is transported out of tranformer (output is shorted
so lots of current flows but no voltage, thus no power, in actual life
there is some voltage so some little power gets here as well).
So that 100W transformer is now taking in 1000W of and outputting
practically nothing, thus there is 1000W power heatring tht transformer
that was designed to handle 10W heating power loss in it...
You can think how quicly and how hot the transformer and wiring
inside it quicly becomes where is one kilowatt of power heating that
quite small transformer!!

As I say, I've been running it a couple of hours so far
and there's been no change. As a matter of fact, a few weeks ago I had
previously removed the heatsink from the output transistors in order to
improve the sound, and there was never any overheating problem.

You stupid! Heatsinks on the output transistors are there
for a very good reasons. The output transistors have considerable
power loss and get hot. If you remove the heatsinks, then the
transistors gets mugh hotter much sooner. When transistor gets
hot it's parameters change, causing first poor operation of
amplifier (worse sound easily), then starting to smell bad
(your figerprints on the cases start buring...), and then transistors
fail short... not always in this order.

Your amplifier if you are lucky might work some time without
the heatsinks if you play at very low volume... if you use
higher volumes or play longer time, it is very propable that sooner
or later your output transistors fail! The hotter they run the
sooner they fail!

So sooner or later I expect that your output transistors will
fail short... this will cause quite propably a chain-reaction
that would in normal case burn your amplifier fuse...
When you have removed the fuse, then in this case I expect you
get the smome coming out sooner or later from your autput
transistors, amplifier power transformer and/or your speakers.
And possibly flames soon after that..

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/