From: Peter Coghlan Sent: Saturday, July 18, 2015 1:27 AM > Rich Alderson <ri...@livingcomputermuseum.org> wrote:
>>> It is generally a good idea to re-form electrolytic capacitors in power >>> supplies, and to bench check the power supplies (under some kind of >>> load) before actually applying power to the whole unit. >> It is always a good idea to replace electrolytic capacitors in power >> supplies. >> The rest of the advice is sound. > Can you please clarify if this statement represents the policy of the Living > Computer Museum or is it something more personal? Perhaps some qualification > or a re-phrasing would be useful as it does not appear to make sense as it > stands? This is the policy of Living Computer Museum. It is based on the cumulative experience of multiple very senior electrical engineers[1] doing restorations here, in conjunction with 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. When, in 2004, we first began restorations of the systems that eventually became LCM, we followed the sage advice of those who described how to "re-form" electrolytic capacitors. Months of frustrating results eventually led to the search for industry literature on the topic; the result of that research was the formulation of our policy regarding this practice--that it is not worth the time and effort for minimal results. > I think you may have seen or participated in some of the many discussions we > have had on this topic on this list? In light of these discussions, I find it > hard to see how a categorical statement such as this one could be justified. Since the proponents of this practice make categorical statements with no evidence that they want to listen to reasoned explanations, I long ago gave over trying to convince them, and simply respond when someone makes a statement to a newbie which will result in frustration and failure for the unfortunate recipient of this advice. Rich [1] NB: I am not now, nor have I ever claimed to be, a hardware engineer of any stripe, and more particularly not an electronics specialist. I am, nonetheless, capable of reading and understanding research papers with statistics that back up the claims being made even if I could not devise the experiment to test them. I rely on my colleagues who are experts to assure me that the writers are not smoking crack. Rich Alderson Vintage Computing Sr. Systems Engineer Living Computer Museum 2245 1st Avenue S Seattle, WA 98134 mailto:ri...@livingcomputermuseum.org http://www.LivingComputerMuseum.org/