Using a Variac to revive power supplies

From: rodsmallwood at btconnect.com To: cctech at classiccmp.org Subject: RE: Using a Variac to revive power supplies Date: Fri, 24 Dec 2010 08:41:09 +0000 I know it's obvious but a Variac is AC out. It's capable of 2.2KVA! You would be relying on the old PSU's transformer and rectifier circuits to generate the reform voltage. DC from a bench PSU across an isolated capacitor via a limiting resistor is probably a better option. As many switchmode PSU's are automatic dual voltage. Usually 110v to 240v They might be OK to run from the Variac. Otherwise probably not. Regards Rod Smallwood -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Tobias Russell Sent: 23 December 2010 14:12 To: General Discussion: On-Topic and Off-Topic Posts Subject: Using a Variac to revive power supplies I've recently acquired a Variac (220V 10A) and was wondering what the collectives views are on using them to revive long dormant power supplies. Previously I have removed the electrolytics and reformed them with a bench power supply setup, slowly ramping up the voltage (as per http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm). Am I right in thinking I can use the Variac to effectively reform the capacitors in circuit? I'm currently rebuilding one of my PDP-8/E's which has a linear PSU which I believe is ok, but will it also work with later DEC switchmode PSUs? All the best, Toby