At 17:19 +0100 1/26/10, [email protected] wrote: >>I'm assuming >> it's an issue with flat PRAM batteries, as I've read that the IIfx >> can't power on without batteries, and the machine hasn't been started >> properly since the end of the last millennium, but I'm just wondering >> if there are any other terrible defects (dead capacitors ect..) that >> may contribute to causing this issue.
I plan, right soon now, to fix my IIFX of its startup problem. Batteries are not the whole problem but it does appear that they need to be right up to new specifications. Somewhere I found this: <ftp://ftp.macnauchtan.com/Circuits/macIIfx_startup.GIF> I'd like to give the originator credit but I donno who did it. Look at C42 which is one of those aluminum electrolytics which are known failure points. Look for acid leaks around the circuitry. I think it is used to provide a larger pulse current than the lithium cells can supply by themselves. C9, C27, and C24 are involved with timing sensitive flip-flop action to make a start and stop action of the pushbutton at the rear work. I'm not sure how critical they are but it would be pretty easy to replace them with tantalum versions. Why Apple's engineers make such a simple concept as start and stop require 8 gates, 3 transistors, and 6 diodes is beyond my ken. My desk lamp does it with one bistable spring. -- -> The US of A is getting pelloreid <- -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
