[time-nuts] aging/failure of un-powered xtal oscillators?

[Jim Lux]

On 5/17/13 5:07 AM, Grant Hodgson wrote:
> A client company has sourced a quantity of 'New in Box' iSBC series
> memory modules manufactured by Intel in the 1980s for a MULTIBUS based
> computer system. These are still in their original, sealed packaging and
> have been stored (for 25 years) in controlled conditions. These cards
> are required as part of a refresh programme for a mission-critical
> application (electricity generation), which are currently using original
> Intel cards from the same era.
>


Oh you lucky devil. Do you have a big beast (MDS80) and an ICE pod as well?

OK.. the actual crystal may have aged or it may not.  The electronics 
might be ok or might not.  Tin whiskers are always an issue, but at 
least with that vintage, all the solder has plenty of lead in it.

I would think that other things than the oscillator would be the 
problem. It's not like ICs just go bad sitting there unpowered: failures 
are due to packaging issues.  Hermetic seals that aren't hermetic and 
stuff like that. Socketed parts are always an issue.

I'll bet a lot of people on  this list are running equipment with boards 
that are 30 years old in them.

Voyager has lots of 40 year old parts and is still working at the edge 
of the solar system (granted, those parts were specially selected..)

I'd just do the things you outlined, power it up, and see if the 
oscillator module is putting out the 64.1 kHz...

Good luck on the DRAM, though.. I spent a LOT of time tracking down 
seeming double bit errors on DRAM multibus memory cards in the 80s, only 
to find that it was timing issues.  Back then, the part timing varied a 
lot from part to part, and PWB design technique was nowhere near as 
sophisticated as it is today in terms of terminations and so forth.