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Re: [Shop-talk] Fuses

To: shop-talk@autox.team.net
Subject: Re: [Shop-talk] Fuses
From: Jimmie Mayfield <mayfield+shoptalk@sackheads.org>
Date: Fri, 12 Jan 2024 10:07:51 -0500
Delivered-to: mharc@autox.team.net
Delivered-to: shop-talk@autox.team.net
References: <OF8EF41E32.05B97747-ON85258AA0.0081822D-85258AA0.0081ECD3@mail.megageek.com> <1370429843.203224.1704977963889@mail.yahoo.com> <OFB52CE02C.CA4D6450-ON85258AA2.003E4560-85258AA2.003E6FE0@mail.megageek.com>
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On 1/12/24 06:21, Moose wrote:
> Dave,
>
> This is brilliant (figuratively AND literally) 8>)
>
> But is this safe?  Couldn't it melt wires if there is a short?

As long as your wire won't melt when powering the bulb directly from a 
power source, it'll be fine.

A light-bulb current-limiter is a technique that techs and hobbyists 
sometimes use when repairing old audio amplifiers.

When the bulb's filament is cold, it has a pretty low resistance so it 
doesn't usually affect the circuit.  A 100W light bulb, for instance, 
has a cold resistance of about 10 ohm.  When plugged into a working 
circuit that doesn't normally carry a lot of current, the bulb's 
filament conducts but not enough to glow.  If there's a short circuit 
somewhere, much more current flows and it all gets dumped through the 
bulb and it gets bright.  Since the bulb is part of the circuit, it sets 
an upper bound on the amount of current that can flow so by choosing 
your bulb carefully, you can protect your fuses and the rest of the 
circuit while you troubleshoot.




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    <div class="moz-cite-prefix">On 1/12/24 06:21, Moose wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:OFB52CE02C.CA4D6450-ON85258AA2.003E4560-85258AA2.003E6FE0@mail.megageek.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <font size="2" face="sans-serif">Dave,</font>
      <br>
      <br>
      <font size="2" face="sans-serif">This is brilliant (figuratively
        AND
        literally) 8&gt;)</font>
      <br>
      <br>
      <font size="2" face="sans-serif">But is this safe?  Couldn't it
        melt wires if there is a short?</font></blockquote>
    <p>As long as your wire won't melt when powering the bulb directly
      from a power source, it'll be fine.  <br>
    </p>
    <p>A light-bulb current-limiter is a technique that techs and
      hobbyists sometimes use when repairing old audio amplifiers.  </p>
    <p>When the bulb's filament is cold, it has a pretty low resistance
      so it doesn't usually affect the circuit.  A 100W light bulb, for
      instance, has a cold resistance of about 10 ohm.  When plugged
      into a working circuit that doesn't normally carry a lot of
      current, the bulb's filament conducts but not enough to glow.  If
      there's a short circuit somewhere, much more current flows and it
      all gets dumped through the bulb and it gets bright.  Since the
      bulb is part of the circuit, it sets an upper bound on the amount
      of current that can flow so by choosing your bulb carefully, you
      can protect your fuses and the rest of the circuit while you
      troubleshoot.</p>
    <p><br>
    </p>
    <br>
    <p><br>
    </p>
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