On Mon, 20 Jun 2005 09:53:49 -0400, "MZ"
wrote:

That's a good point. If the problem turns out to be a component
inside the amp instead of just a blown fuse, it could have easily
happened because of the "inrush curent" through cold circuits when you
turned the amp on. (The same reason light bulbs usually blow when you
first turn them on.)

Amps are usually protected from voltage spikes and drops while you're
starting your car, since the amp is turned on by the remote turn-on
lead on the head unit, and there's usually a relay in your car's
wiring that keeps things like the air conditioning and head unit
turned off while the engine is being started.

But with the light bulb, it's because the resistance of the tungsten is at
its lowest point when cold. Things are different with an amp. Charge up
the power supply capacitors and that's it. What's gonna go wrong there?
Burn out a trace?

I guess it would depend on what the very first components are in the
circuit path when power is applied. The capacitors you mention appear
as dead shorts in the circuit until they've begun to charge, so that's
another example of a spike in turn-on current. Along the same lines,
what exactly is it that causes "turn-on 'thump' in amps"? Even if his
amp has circuitry to prevent the "thump", that circuitry itself must
have to deal with some kind of spike upon turn-on.

I realize it doesn't happen often, although I've had other electronic
devices fail upon initial powerup. The original poster was asking why
his amp would fail at turn-on rather than under use, and I was just
pointing out that initial application of power can be a risky time for
electronic devices.

For his sake, I'm hoping the problem is just a blown fuse in the bad
channel. The last I heard from him, he had just looked at the fuse in
place - he hadn't removed it to examine it more closely, test it with
an ohmmeter, or to swap it with the other fuse in the amp or a new
fuse.


--
Scott Gardner

"If you sleep twelve hours a day, then the deployment will only be three months long, not six!" (Navy JO saying)