On Mon, Jul 20, 2015 at 4:46 PM, Rich Alderson <ri...@livingcomputermuseum.org> wrote: > industry white papers with tables of decay rates for > the aluminum electrolytics that indicate that, *no matter what*, they lose > capacitance over time, until c. 14 years from manufacturer date they are at > 10% > of rating.
That's very interesting. I haven't seen those white papers, but the "no matter what" must in fact depend on something, since on the PDP-1 Restoration Project we found that most of the 40 year old aluminum electrolytic capacitors still met their original specifications, including capacitance within rated tolerance. Of the few electrolytic capacitors that had failed, the problem was a catastrophic failure, not the capacitance being outside the rated tolerance. In the PDP-1, we preferred to keep the original components as much as possible. Had there been a capacitor, the failure which would have caused extensive damage to other components, we would have given serious consideration to replacing it. However, that was not the case for any of the capacitors in the PDP-1. Had our analysis indicated any expected benefit to replacing all of the electrolytic capacitors, we would have done so, and bagged and tagged the originals similar to what we did with failed components, so that they could be replaced if it ever was desired to return the artifact to its pre-restoration condition. I'm not recommending against LCM's policy, but I also wouldn't necessarily encourage anyone to adopt it, nor to adopt the practices of the CHM PDP-1 Restoration Project, without studying the issue. Eric
