How long do old circuits/electronics last for?

who the f*ck cares. You'll be dead by then anyway.

Do you mean if they're left unused? If in constant use, something will fail sooner or later.

Larger geometry chip internals of that era will last longer than modern small geometries, due to cosmic ray damage and tin-whisker growth. Metallisation creep will eventually destroy the older ones with or without non-hermetic seals and airbourne corrosion ingress

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

snipped-for-privacy@yahoo.co.uk wrote in news:c549b51c-7ef3-4b82-9daa- snipped-for-privacy@v3g2000hsc.googlegroups.com:

In addition to the comments others have made, there are a couple of other factors

1) fungal growth, insects, rodents, can destroy electronics. MIL SPEC equipment receive special coatings and treatments to reduce these problems. Most civilian items do NOT. 2) ceramic capacitors 'age', decreasing in value from the last time they were 'deaged'. Deaging occurs when the capacitor is heated above the Curie point of the ceramic. Aging rate depends on the formulation of the capacitor's ceramic. High K ceramics can decline in value by as much as as a few percent per decade. A decade = log(time since last deaging) So if the cap drops 1% in the first hour after deaging, it drops 2% in the first 10 hours, it drops 3% in the first 100 hours it drops 4% in the first 1000 hour, it drops 5% in the first 10000 hours, etc.

Almost all components age in some way. When the value of any component gets outside the design limits of the circuit, the circuit stops working as it was intended.

--
bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

bz+ser@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

Part of what the OP is asking is whether devices inherently deteriorate * / self-destruct, even when not being used, or they have to be in use to fail.

The answer is that almost everything eventually falls apart, whether or not it's in use.

Of all components, I'd expect vacuum tubes to last the longest -- perhaps hundreds of thousands of years -- simply because glass is highly stable, and the internal metal elements are in a vacuum, where "...rust doth [not] corrupt".

• Don't say degrade. Degrade is a transitive verb.

/

fail.

not

and

I always wonder why air does not pass between pins on the base and the glass of the envelope. Unless knocked or cold effects they are highly reliable, despite , i would have thought. glass/metal (even without corrosion) would be suspect over time

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Not actually true. Over time their characteristics drift from ionic contamination mainly IIRC and the emissivity of the cathode gradually reduces too. I've seen tubes that have actually gone zero emission even though the filament still works.

Graham

"N Cook" wrote in news:fr5uj0$i8e$ snipped-for-privacy@inews.gazeta.pl:

It can't. There is no room.

The metal is first treated to form a layer that will chemically bond with the glass. A layer of glass is then put onto the lead. It 'wets' the lead, bonding to it strongly. This glass must have the SAME coefficient of expansion as the metal!

In general, there may be several different layers of glass applied, each with a slightly different coefficient of expansion. Finally, the base of the tube is molded around the set of leads, the electrodes are spot welded to the leads, the envelope is applied, the vacuum is pulled and the tube is sealed and the 'getter' is fired'.

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

bz+spr@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

TVs and radios with valves ( tubes) close to for ever but unfortunately limited to their weakest link, the capacitors. They are good for 35 years then dry up.

Modern electronics are probably good for 20 if they are of the highest quality. Computers somewhere around 8 years because of crappy capacitors on the motherboards. MP3 players roughly 2 years because of planned ( by design) obsolescence.

In general the main culprits for old equipment dying are bad caps, wiring that becomes brittle. Solder joints that become brittle or cold joints over the years of hot/cold cycles. Traces on circuit boards may also lift with repeated on/off cycles ( heat) over time.

But the biggest reason for old electronics no longer being around after a few years is that my wife will get a hold of everything when I am on a business trip and chuck it all out on garbage day.

old electrolytic and paper capacitors will most likely be duds as they dry out. construction quality of other components makes a difference; how tightly metal caps are crimped to carbon resistor elements, for instance (i have a story...), how well sealed the innards of a component are against moisture, etc.

then there's the circuit boards themselves, for equipment which has them. open a military piece of equipment and a consumer piece of equipment, even an expensive one, and compare.

"professional" stuff can be well built; a few years back i found a fender guitar amp that had either fallen or been tossed from a vehicle and buried in a snowbank; a branch had stuck through the speaker cone. i replaced the speaker and the power switch, whose toggle had been broken off, and it worked fine ever since. but the quality of circuit board inside looked milspec.

Depends on what you mean by 'modern'. I've got solid state equipment from the era the OP mentions (70's), most of which is working fine. I have computers older than eight years which also work fine...for what they're worth.

IME, the main problems with older computers is the onboard battery backups dying. Caps, except for the infamous problem--largely dealt with by now--with bootleg electro's a few years ago, have not been that much of an issue.

It's worthy of note that the Voyager probes have been operating in the most extreme conditions for over thirty years now. They're expected to continue working until the 'batteries' go dead, no sooner than 12 years from now.

jak

s

on

Very many thanks everyone - all your comments have been very helpful. Additionally can I just ask about how long light emitting diodes last for? Also processors (cpu chips) on motherboards? Lastly when did engineers start building electronics with planned obsolescence - is this a recent thing? thanks again

Most parts like that could last 100 years if not abused, though flash RAM may lose the data. Use and environment will have a larger effect on life than anything else.

Planned obsolescence is largely a myth. No engineer that I've met designs something specifically to fail. Rather they design something to be as cheap to produce as possible, while still lasting "long enough". This is nothing new, it's been going on for decades.

good point, but let's now add the lack of availability of spares and service documentation to a lot of this stuff. This probably is an even greater cause of its reduced life!

-B

Again it all comes down to cost. Companies produce what the consumer demands, and most consumers will not pay a dime more for something that has parts and service documentation available a few years later than for something that does not. I would, because I service things and expect them to last, but to most people, appliances are disposable and are thrown away when they break.

I've seen a lot of cases where tubes that weren't used for many years took some time to 'wake up'. At first they test bad and perform poorly, but after a few hours, they test strong and work well. This is particularly common with old CRTs that haven't been used for 20 or

30 years. Andy Cuffe

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