[aprssig] Amazing resistors

Scott Miller scott at opentrac.org
Fri Sep 5 19:32:27 CDT 2014


I did this several years ago with 200 lb test Spectra line and found I 
could push metal film resistors even further.  It'd melt the solder off 
before the resistor would burn out.

Scott
N1VG

On 9/5/2014 5:10 PM, Robert Bruninga wrote:
> We have been running a 0.25 Watt small resistor at 3.5 Watts ALL DAY and
> it still wont burn out!
>
> We were using it as a "burn resistor" to release a fishing line mechanism.
> It does that in 2 seconds.  But now 10 hours later it is still going and
> wont burn out!  (We had hoped it would eventually open so that we could
> use the same control line for something else after the resistor opened up.
> But it wont.
>
> This is amazing to me.  We know that an old composition resistor will burn
> smoke and crack in only a few seconds at these power levels, but not the
> carbon film at 14 times overload!
>
> Here is the scenario:  7.5v across a 15 ohm  0.25W carbon film resistor.
> . It burns the fishing line in 2 seconds
> . It begins to smoke at 5
> . It smokes for a minute or so
> . Then, is black, but no further visible changes
> . After an hour it has changed resistance to 20 ohms
> . After 5 hours it is up to 29 ohms
> . After 10 hours it is up to 35 ohms
> . Of course the V^2/R power is going down, but it wont burn out!
>
> Just thought you might find this data point useful!
>
> Bob, WB4APR
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