[Amps] Babying radios conclusion

[Roger (K8RI)]

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.
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> 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..............
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> 1. If a tube is left on, under continuous proper usage and under correct load, what causes it to fail ?  And, what is "soft"?
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> 2.  Same question for transistors.
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> 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)

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> 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).
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> 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.
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> 73
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> Charles Harpole
> k4vud at hotmail.com 		 	   		
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