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preserve electronic devices

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coppercone2:
put deoxit on the terminals and put it in a box and forget about it. Moisture proof box with silica gel is as far as I would ever go.

ConKbot:
If you're going as far as adding silica gel packets, you can also add hand-warmers as an oxygen absorber. They are iron powder, salt, and vermiculite, so in a dry environment, shouldnt be emitting anything nasty. That will give you a dry, reduced oxygen environment with readily available products, without having to deal with trying to get a good gas purge, or handling a gas cylinder.

TerraHertz:
Entropy comes in many forms.

Dust - Looks bad, can also be corrosive.
Moisture - corrosion.
Bugs - they chew, pee and poop, plus leave carcasses. All destructive, often corrosive. Often they really like making homes in electronics.
  Large, thick ziplock plastic bags and sealed containers are good against these. Especially if moisture absorbing packs included.
  In Oz stores Coles & Woolies) there's a brand 'Hercules' with a large size 27 x 33 cm and double ziplock. Packs of 40. I use a lot of these, especially to preserve old manuals.

Light - discolors plastics, causes some materials to decay. Store in cupboards, boxes, etc.
    Some plastics go brown with age, due to included Bromine flame retardants. This can be reversed; look up 'retrobright'.
Air - oxidation, especially of contacts made of anything but gold.
   Nothing you can do about this, unless you can arrange long term storage in dry nitrogen or argon. Difficult.
Paper:
  Embrittlement and yellowing of cheap acid paper. Not much can be done to stop this.
  Mildew - keep as dry as possible, stable cool temp. Bagged.
  Silverfish - Bagged or boxed, plus sprinkle camphor flakes in the containers.

Batteries - the _worst_ destroyers of old electronics. Especially check for built-in nicads and other small soldered-in batteries.
  All batteries MUST be removed from anything to be stored long term.
  Leaking nicads especially can irreparably destroy all electronics within a large radius.

Tin whiskers - anything tin plated (with no lead alloyed in) will grow microscopic 'whiskers' of tin, that can short out and damage electronics. Slow but deadly. Inspect before powering, brush off. If on the inside of components - tough luck.

Depolymerization. Rubber parts, feet, and 'grippy' surface coatings turning to sticky liquid gunk, plastics going brittle, etc. VERY hard to remove. The only defense is to check items now and then, and completely remove any rubber parts showing signs of going tacky.

Rubber belts and rollers. You're going to have to replace them, repeatedly in the long term. Find a supplier.

Urethane foam. Commonly used as air filters, sound absorbing and anti-vibration pads. This stuff disintegrates into tacky, corrosive gunk that gets all through equipment. Remove on sight, clean all residue.
Where used in storage boxes to cushion expensive, delicate test gear, replace ASAP with non-decaying foam such as polyethylene. Nothing worse than opening such a box to find some priceless precision metal device corroded to hell.

Flexible plastics losing their volatile plasticiser substances and going brittle.
Cables especially. Anything where thin plastic is used as a hinge.

Hard plastics kept under tension. Will always crack eventually, even if glass fibre reinforced. Self tapping screws in plastic mounting posts for example. Also plastic clips used to retain clip-on covers.

Plasticiser compounds diffusing out of one substance, and damaging nearby incompatible substances. For eg, flexible PVC cables pressed against some kinds of hard molded plastics, will 'melt' indents into the plastic.
Also with toner-based photocopies in PVC binders, the PVC plasticisers will make the toner melt and adhere to facing pages and the binder.

Grease, on moving parts. Often hardens with age. Eg old floppy disk drive mechanisms, pot shafts, etc.
  Can be very difficult to remove once it's really hard. Also may be corrosive.
  Remove with IPA, acetone or other solvents. Experiment. Disassembly may be required. Sometimes only mechanical scraping works.
  Replace with non-hardening Lithium soap or synthetic grease types. Sometimes the right viscosity matters.

Some component types are just plain doomed.
  Carbon composition resistors all drift high with age, going out of tolerance. Faster if operating hot.
  Filament light bulbs (eg indicators, spinner knob sensors, etc) just plain always fail.
  Membrane keys - don't have long lives.
  Silicone rubber pad keys - don't get oils on these. Oil diffuses through the rubber, gets into the conductive pad underneath, and makes it non-conductive. Can sometimes be restored by soaking in solvents.
  LEDs fade with age.
  RIFA mains-rated caps - the outer encapsulation shrinks and cracks, lets moisture into the plastic metalised film, under voltage the film breaks down and arcs. Result - a lot of very stinky, gunky smoke that condenses on surrounding parts and is hell to clean off.
  Remove and replace all RIFA mains caps on sight.
  Electrolytic caps. They all fail eventually. Only the duration varies. For cheap or underrated ones, a few years. Good ones not stressed, can last decades.
  Wet foil tantalum caps with non-ceramic seals - all fail eventually.
  Memory devices using charge retention in cells. eg EPROMS, flash memory... data retention time is not forever, but varies a lot between device types and manufacture. All should be read out and archived if at all possible.
  One-time programmable devices - gate arrays, etc. Especially fuse link types. They can randomly fail. But many are not readable, or have read protection enabled. Read if possible, or try to obtain source code, spare blanks and suitable programming device. But accept that devices using a lot of custom programmed devices are going to die unrepairable eventually.
  Non-volatile memory of the static RAM plus encapsulated battery kind, Dallas, etc - arrgh. Guaranteed fail in a decade or two. There are hacks online for cutting down into these and attaching new external battery. Good luck. Fortunately their contents can usually be read out in a device programmer.

schmitt trigger:
Thanks for your very detailed explanation.

I have experienced depolimerization.  It was a big mystery to me until you explained it above.

CatalinaWOW:

--- Quote from: TerraHertz on October 25, 2020, 11:42:04 am ---Entropy comes in many forms.

Dust - Looks bad, can also be corrosive.
Moisture - corrosion.
Bugs - they chew, pee and poop, plus leave carcasses. All destructive, often corrosive. Often they really like making homes in electronics.
  Large, thick ziplock plastic bags and sealed containers are good against these. Especially if moisture absorbing packs included.
  In Oz stores Coles & Woolies) there's a brand 'Hercules' with a large size 27 x 33 cm and double ziplock. Packs of 40. I use a lot of these, especially to preserve old manuals.

Light - discolors plastics, causes some materials to decay. Store in cupboards, boxes, etc.
Air - oxidation, especially of contacts made of anything but gold.
   Nothing you can do about this, unless you can arrange long term storage in dry nitrogen or argon. Difficult.
Paper:
  Embrittlement and yellowing of cheap acid paper. Not much can be done to stop this.
  Mildew - keep as dry as possible, stable cool temp. Bagged.
  Silverfish - Bagged or boxed, plus sprinkle camphor flakes in the containers.

Batteries - the _worst_ destroyers of old electronics. Especially check for built-in nicads and other small soldered-in batteries.
  All batteries MUST be removed from anything to be stored long term.
  Leaking nicads especially can irreparably destroy all electronics within a large radius.

Tin whiskers - anything tin plated (with no lead alloyed in) will grow microscopic 'whiskers' of tin, that can short out and damage electronics. Slow but deadly. Inspect before powering, brush off. If on the inside of components - tough luck.

Depolymerization. Rubber parts, feet, and 'grippy' surface coatings turning to sticky liquid gunk, plastics going brittle, etc. VERY hard to remove. The only defense is to check items now and then, and completely remove any rubber parts showing signs of going tacky.

Rubber belts and rollers. You're going to have to replace them, repeatedly in the long term. Find a supplier.

Urethane foam. Commonly used as air filters, sound absorbing and anti-vibration pads. This stuff disintegrates into tacky, corrosive gunk that gets all through equipment. Remove on sight, clean all residue.
Where used in storage boxes to cushion expensive, delicate test gear, replace ASAP with non-decaying foam such as polyethylene. Nothing worse than opening such a box to find some priceless precision metal device corroded to hell.

Flexible plastics losing their volatile plasticiser substances and going brittle.
Cables especially. Anything where thin plastic is used as a hinge.

Hard plastics kept under tension. Will always crack eventually, even if glass fibre reinforced. Self tapping screws in plastic mounting posts for example. Also plastic clips used to retain clip-on covers.

Plasticiser compounds diffusing out of one substance, and damaging nearby incompatible substances. For eg, flexible PVC cables pressed against some kinds of hard molded plastics, will 'melt' indents into the plastic.
Also with toner-based photocopies in PVC binders, the PVC plasticisers will make the toner melt and adhere to facing pages and the binder.

Grease, on moving parts. Often hardens with age. Eg old floppy disk drive mechanisms, pot shafts, etc.
  Can be very difficult to remove once it's really hard. Also may be corrosive.
  Remove with IPA, acetone or other solvents. Experiment. Disassembly may be required. Sometimes only mechanical scraping works.
  Replace with non-hardening Lithium soap or synthetic grease types. Sometimes the right viscosity matters.

Some component types are just plain doomed.
  Carbon composition resistors all drift high with age, going out of tolerance. Faster if operating hot.
  Filament light bulbs (eg indicators, spinner knob sensors, etc) just plain always fail.
  Membrane keys - don't have long lives.
  Silicone rubber pad keys - don't get oils on these. Oil diffuses through the rubber, gets into the conductive pad underneath, and makes it non-conductive. Can sometimes be restored by soaking in solvents.
  LEDs fade with age.
  RIFA mains-rated caps - the outer encapsulation shrinks and cracks, lets moisture into the plastic metalised film, under voltage the film breaks down and arcs. Result - a lot of very stinky, gunky smoke that condenses on surrounding parts and is hell to clean off.
  Remove and replace all RIFA mains caps on sight.
  Electrolytic caps. They all fail eventually. Only the duration varies. For cheap or underrated ones, a few years. Good ones not stressed, can last decades.
  Wet foil tantalum caps with non-ceramic seals - all fail eventually.
  Memory devices using charge retention in cells. eg EPROMS, flash memory... data retention time is not forever, but varies a lot between device types and manufacture. All should be read out and archived if at all possible.
  One-time programmable devices - gate arrays, etc. Especially fuse link types. They can randomly fail. But many are not readable, or have read protection enabled. Read if possible, or try to obtain source code, spare blanks and suitable programming device. But accept that devices using a lot of custom programmed devices are going to die unrepairable eventually.
  Non-volatile memory of the static RAM plus encapsulated battery kind, Dallas, etc - arrgh. Guaranteed fail in a decade or two. There are hacks online for cutting down into these and attaching new external battery. Good luck. Fortunately their contents can usually be read out in a device programmer.

--- End quote ---


Great summary.  Good advice for anyone truly serious about long term preservation.

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