Better later than never, as the historical importance of these earlier forum threads (and the units they supported) shouldn't be relegated to the rubbish bin.

As far as old technologies are concerned, yes- it's possible that an EPROM could go bad with age, certainly older backup batteries can, but the number one thing that will fail statistically is capacitors! Silicon-based devices are actually pretty stable, and unless overstressed by too much current demanded of them, or an overvoltage condition, they can last decades in a well designed circuit. Resistors fair well also, and certain film and ceramic capacitors can as well, but electrolytics are generally notorious for "drying out", or requiring sustained voltages or application of varying voltages to "fully form".

In an earlier post altruistica had mentioned that his Non-Working MTS-1000 suddenly sprang back to life. It's not unheard of for capacitors to do this- to be marginal until subjected to something like an actual in-circuit condition for a while.

There are many other conditions that are tricky in actual electronic devices, such as thermally related failures (usually intermittent ones) which might come from flaky, cracked or marginally "cold" solder joints (solder, if viewed in the very large timescale is actually a liquid- it can "cold flow", much like glass). Oxidation is obviously another thing that can affect older circuits- scrubbing or chemical cleaning of header pin connectors is advisable, for example, or occasionally (and very carefully) removing and re-inserting removable IC's from their sockets (to "freshen up" the contact pins) can be helpful.

For my money, I would start troubleshooting NW units in the following ways:
1. "Idiot check" for the obvious: unit properly plugged in, power switch on, fuses not blown, interconnect cables properly made, "volume" pots or other controls such as switches in a "neutral" state, etc.
2. Check for bulging, or leaking electrolytic capacitors (look for a shiny or sticky residue around the capacitor ends) - if necessary remove a suspect electrolytic and either replace immediately with a new one or test it with an LCR meter before returning it to its in-circuit position (always observe polarity when replacing polarized electrolytics).
3. Look for component "browning" of resistors which indicates an overheating condition. Likewise check the areas of the PCB's themselves for "browning" , which may indicate an overheating condition, particularly near higher-powered circuit components, such as voltage regulators.
4. With circuit turned on, very carefully feel the tops of IC's etc. for too much heat (do not ever touch bare metal, such as conductive leads, pins etc., or the backs of voltage regulators- which are often carrying a voltage). Better yet, use one of those non-contact Infra-Red thermometers, and check for elevated temps of particular devices including diodes, caps and resistors, as well as IC's.

Beyond these initial checks (which can be made by anybody with minimal tools required) solutions would probably require tech-like troubleshooting with scopes, meters, signal generators, or other more sophisticated gear. Occasionally some correctly applied intuition with a complete and accurate set of schematics can yield results on its own, but usually some knowledge of the "Theory Of Operation" of a given circuit design will be required.

So speaking of the practical, did anyone posting here manage to off-load the EPROM image files for the MTS-1000 and save them to hard disc? If so would you please consider posting the ".bin" files to a website like someone here had suggested? At least the rest of the world could possibly reconstruct future EPROMS for those of us who don't have an EPROM reader/burner. Thanks for all your help.