I apologize for the question, but I have many doubts regarding some answers found on the web.In the past I powered an old Apple IIe, which had been at a stand still for several years, obtaining the "cooking" of the infamous RIFA 0.47 uF power supply capacitor; the problem was solved by replacing the capacitor.Now I have to revitalize another computer, my question is this:Does it make sense to use a variac to progressively power the computer?Would I have saved the original capacitor with this procedure?If so, what is the feeding progression to use?With what tension to start and how to understand when and to what extent I can raise the tension?Once I reach my voltage (220V) and the computer works, the next time I feed it, can I connect it directly to 220V, without using the variac?
Thank you for any useful information.
Short answer: NO.
You are thinking about the reforming of old electrolytic capacitors. Modern switching power supplies will not be happy with your idea of slowly increasing voltage using variac.
The RIFA caps are failing due to breakdown over time. If you look at one before it gets powered up, you can usually tell it'll be failing shortly anyway. They "maze" with the skin becoming cracked all across.
Chesh
I understand; I didn't think switching power supplies were already in use at the time of the Apple IIThe RIFA that I had replaced had a perfect appearance that respected my idea of restoration.Is this capacitor okay?https://www.ebay.com/itm/254936424473It is X2 type so the application is appropriate, but the RIFA filter capacitor on Apple power supplies is typically 0.1 uF.
My preference is this or similar. X2 rated: https://www.digikey.ca/en/products/detail/kemet/PHE840MB6100MB05R17/1927371
OP stated this is a 220v psu. Assuming it's the ASTEC AA11042/C / 699-0161-A, then based on the cap list on Console5, the 220 psu uses two mains caps: .1 and .47. Both should be replaced, as it's just a matter of time before the other one blows. The apppropriate safety rating should be used on both. Without a schematic handy, not sure what that would be for each specific cap.
C1 0.1uF 250VAC Safety Cap
C2 0.47uF 250VAC Safety Cap
I purchased https://console5.com/store/apple-2-power-supply-cap-kit-p-n-605-5703-astec-aa11040b-aa11040-b.html and then went ahead and replaced all of the caps. You can read about all of that at https://www.applefritter.com/content/apple-ii-plus-capacitor-replacement.