On 2/23/2015 11:58 PM, Brent Hilpert wrote: My experience is different. 1940's through 1960's -- I replace all AECs because most are either bad or too far on their way out. 1970's-1980's, depends on too many variables to give simplistic rules, but I will test and reform all AECs. Some are found to be bad, but most are still ok -- again, depending on many factors. 1990's onwards, I don't worry about as there's rarely a failure (unless of those bad Chinese variety). ** I do, all the time, as per above. ** I don't concur with this statement because the charge rate is too high. Countless times, there's been caps I couldn't reform with too high a charge rate, but when it was slowed down, they came back around. Many factors are at play.. amount of leakiness to begin with, level of operational voltage vs. cap's rated voltage, etc. BUT, AECs *do* benefit from and *do* require periodic use... which keeps them from losing their oxide layer to a certain degree (within the circuit's applied voltage range). ** Because they go bad... even those big computer grade ones. I've got a whole bucket here full of them. ** Here, agreed.... *blanket* replacement isn't.. but they should all be checked. ** 1980's DEC stuff still seems to be OK, although I frequently find bad caps in the 3rd party power supplies like those from Astec (eg. BA123, BA23)... but ALL the AECs benefit from reforming -- you can see right then and there how they do, how they perform before and after. And you can tell whether a cap does or not by how it RESPONDS during the reforming process. 1970's DEC PSUs like for an 11/34 also have bad caps in them by now.... I just rebuilt 6 modules, and all had at least one bad AEC... now, mind you, most not to the point where the PSU had actually failed completely, but to where it *would* have. I don't replace caps but reform them if their performance during the reforming process indicates that they still have plenty of life left in them. I reform instead of replace when I can in order to save money, and because going through the process of finding the right sizes and right models is a real major pain in the ass. - J.

On Mon, 23 Feb 2015, Brent Hilpert wrote: To be clear, I'm not in the business of arcade machine refurbishment, however I know many people who are. When these machines are used in an arcade environment, they are often powered on 24/7/365, not really unlike a vintage computer coming out of a production environment (and they also suffer from the same sort of TTL logic chip failures we've discussed here on classiccmp). More often than not, when a "vintage" 80s/90s coin-op machine is being refurbished or having extensive maintenance done, all of the electrolytics in the monitor chassis and PSU (linear or switchmode) get replaced as a maintenance item. Some of those machines later end up back in the field earning revenue for operators, but a large portion of them end up resold to individuals too. When you look at the construction and chemistry of aluminum electrolytics, the fact that they are as reliable as they are is quite amazing. The typical part is rated for 2000 hours at either 85C or 105C (even less for some older or specialty parts), at its maximum ripple current. The life of the part also doubles for every 10C below its rated temperature. Say a nearly ubiquitous 85C part is used at very reasonable 40C (104F). That 2000 hour rated part then has an estimated lifespan of 48,000 hours at its maximum ripple current (more often than not, parts are not operated at anywhere near their maximum ripple current, so the expected life is going to be even longer). Just for simplicity, say the part is operated at a low enough ripple current where that 2000 hour part is then good for 100,000 hours (which is of course being /very/ generous). That still only works out to about 11.5 years of expected service life. Larger more modern or high temperature rated parts may have a rated life of 3000 or 4000 hours, but older parts made in the 80s and 90s are still largely going to be in that 2000 hour ballpark. It is 2015, so just going with 2015 - 12 = 2003, I'd say the typical aluminum electrolytic operated at an average temperature present in a monitor, switch mode PSU, etc (higher than 40C) from the 1980s or 1990s which has seen daily or regular use is /probably/ going to be at or near its rated life expectancy. Since a picture is worth a 1000 words, here are some photos of actual failed computer gear that was made in the 1990s. This gear was used by me in a home environment so it wasn't even subjected to the sort of heavy use/abuse found in a commercial setting. This one is a photo of a 12V/5V DC power supply from an external SCSI drive enclosure made in 1992 where the Nippon Chemi-Con KMF series capacitors are leaking their electrolyte out of bottom around the rubber end seals: http://strudel.ignorelist [dot] com/~tothwolf/classiccmp/Electrolytic_Capacitors/autec_powersupply.jpg Here are the parts I'll be using when I rebuild it: http://strudel.ignorelist [dot] com/~tothwolf/classiccmp/Electrolytic_Capacitors/autec_powersupply_parts.jpg This is a photo of the board from a USRobotics Courier V.Everything modem. The three small radial Nichicon PL series capacitors are leaking electrolyte out the bottom around the end seals. Look near the empty U21 location and you can see corrosion just beginning to form: http://strudel.ignorelist [dot] com/~tothwolf/classiccmp/Electrolytic_Capacitors/usr_courier_veverything.jpg The main filter capacitors are also out of spec, and the modem's speaker emits a constant digital "hiss" sound (which is an extremely common fault with these modems since the original capacitors run moderately hot due to passive cooling). You'll also notice USR used 4 horizontal chip-type aluminum electrolytics on this particular board (there are several versions of these modem boards which use slightly different parts). Those particular chip-type electrolytics are no longer manufactured, and since those type are also known to be problematic and eventually leak, they will be replaced with common radial types stuck down to the board. These are the replacement parts: http://strudel.ignorelist [dot] com/~tothwolf/classiccmp/Electrolytic_Capacitors/usr_courier_veverything_parts.jpg This particular modem was one of the best ever made, but every single one that I own (I have at least 4) has the same problem with the main filter capacitors being out of spec causing hiss from the speaker and the smaller 6.3mm Nichicon PL series parts beginning to leak electrolyte. These are just two out of about 250-300 projects currently in my queue (each has a parts bag just like the two I photographed). Both of these two are pre-"capacitor plague" with all the problems starting around 2000-2001 with the cheaply made ultra-low ESR parts swelling up and popping their top vents. -This- is one of the reasons why I'm for replacement of these sort of aluminum electrolytics as preventative maintenance in older gear. You wouldn't have expected either to fail, but they did. How often are you going to pop the top on something like an external modem and inspect, let alone test the electrolytics?