The components which "age faster" (citing you) at full load must age only due
to increased heat, as per your logical answers.
However, a well designed unit should have adequate cooling provided. I guess
that the physical size of the transistor, for example, limits how much heat it
can dissipate regardless of the cooling (not refrigerated, of course_).
If that is true, and it probably is, then one can baby a RF transistor by
running it at less than full rating. The likely result, however, is so small,
as you say, that over a normal ham rig's lifetime (it being retired for reasons
other than failure), the "saving" is trivial.
Thanks,
Charles Harpole
k4vud@hotmail.com
----------------------------------------
> Date: Fri, 15 Jun 2012 00:25:24 -0400
> From: k8ri@rogerhalstead.com
> To: amps@contesting.com
> Subject: Re: [Amps] Babying radios conclusion
>
> On 6/14/2012 11:49 PM, Charles Harpole wrote:
> > >From all generous replies and my reading Google hits, I conclude that the
> > >only way to "baby" a radio is to leave it always on or always off.
> >
> >
> > As my msg say, I asked to eliminate considerations of "mfg defects" or
> > "misuse" (and poor design that traps heat, etc.). These matters were what I
> > specifically eliminated in my questions. I wanted to know if the owner
> > could do anything to baby a well designed, correctly operated radio. The
> > owner can control the heating and cooling cycles of the radio, which seems
> > to cause problems, so I do have AN answer, but..............
> >
> >
> >
> > 1. If a tube is left on, under continuous proper usage and under correct
> > load, what causes it to fail ? And, what is "soft"?
> >
> >
> >
> > 2. Same question for transistors.
> >
> >
> >
> > Especially for transistors because they are inert devices that do not need
> > to heat up to work, and are made of sand.
>
> Not exactly. Only half sand...IE, sand is quartz SiO2, The solid state
> devices are generally made of either Silicon or Germanium although there
> is a layer of oxide in there.
>
> Solid state devices do age. Older devices age more and faster than most
> of the newer ones due to impurities in the Silicon.
>
> The transistor is created on a Silicon wafer. The wafer is heated and a
> layer of oxide is formed on the face. With wafers of 14 inches in
> diameter you can create a lot of devices with closely matching
> characteristics which reduces the price considerably. Of course large
> transistors will have a much lower yield per wafer than small ones.
>
> BTW every wafer created creates a 50% loss of Silicon from the sawing
> and polishing operation.
>
> Junctions are created by etching a pattern in the oxide and then heating
> the chips (many devices are usually created on one wafer) while passing
> a gas containing the dopant material which difuses into the Silicon. In
> an NPN transistor the base Silicon is doped with a material adding an
> excess of electrons. Then the P type gate is added.
>
> With age, the dopant atoms slowly migrate across the junction which
> contaminates the junction. Heat accelerates the aging process.
>
> This is not the only contributor to the aging but it's a sufficient
> example and beyond here it gets quite complicated.
>
> So, yes transistors do age. Running them near their limits will cause
> them to age faster. However with modern devices the aging *Usually*
> takes many thousands of hours. With all the other components mixed in
> there with them I doubt with normal use it would make little difference
> whether you leave them on or switch them on and off. The solid state
> devices are far more reliable than tubes and likely most of the other
> components in the rig as well. OTOH they are far more sensitive and
> less tolerant to over voltage or spikes of even short duration than are
> tubes.
>
> 73
>
> Roger (K8RI)
>
> >
> >
> >
> >
> >
> > Post script... Running a transceiver at less than its rated RF output DOES
> > NOT "SAVE" it from wearing out, IF its heat dissipation is correct. However
> > heat does seem to accelerate the degradation of many components. Too, most
> > things made with plasticizers (like DVDs and some circuit boards) will see
> > evaporation of the plasticizers by the nature of the chemistry of the
> > materials. Chemical/physical interaction of dissimilar metals bonded
> > together cause the metal lower on the Chart of Elements to gradually lose
> > its molecules (why that action is not immediate is a puzzle) which is why
> > antenna connections fail, for example, where copper and aluminum are
> > joined. Another matter not under the control of operators is "cold flow"
> > inside a curve stressed coax cable, for example, but it also takes time.
> > The idea of slowly raising the voltage on a tube filament upon "turn on"
> > remains a disputed area (to do or not to do, that is the question).
> >
> >
> >
> > So my questions 1 and 2 remain in my weak mind. But, I am sure right now
> > that a ham operator can NOT "baby" his correctly designed and correctly
> > operated radio after he turns it on and uses it.
> >
> >
> >
> > 73
> >
> >
> >
> > Charles Harpole
> > k4vud@hotmail.com
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
>
>
>
>
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