I'd figure out where the yellow HD power wire connects to the analog board and visually inspect any filter caps (~1000+ uF) in the area. From the googling I've done and images in the links below it doesn't look like it's easy to trace without taking the board out of the chassis.
http://appletothecore.me/files/mac_tv_restoration.php http://www.mactalk.com.au/62/119154-colour-classic-analog-board-repair.html (This appears to be about the LC 5xx as well...) The other option - if you don't have a known good HD to swap in as discussed by Mack & Dylan - is to attach a voltmeter to the 12V rail and see if it is stable when the HD tries to spin up. If it doesn't you'll see the voltage dip a bit when the disk tries to go. It's easiest to see on and analog VOM but a DMM should work as well. On Thu, Dec 29, 2016 at 6:05 PM, John-Robert La Porta < johnrlapo...@gmail.com> wrote: > Jon, thank you very much for that...I was unaware of how that works. DO > you have any idea and/or way for me to actually trace down that line and > associated components? > > On Thursday, December 29, 2016 at 5:54:28 PM UTC-5, Jonathan Morton wrote: >> >> >> > On 30 Dec, 2016, at 00:38, John-Robert La Porta <johnrl...@gmail.com> >> wrote: >> > >> > Anything that might cause the machine to work fine, but not power the >> HD correctly to be able to spin up? >> >> HDD motors are normally powered from the 12V line. In old computers >> everything else of note is on the 5V or 3.3V lines. It’s entirely >> plausible for the 12V line to fail while the others still work. >> >> - Jonathan Morton >> >> -- > -- > ----- > 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 vintage-macs@googlegroups.com > To leave this group, send email to vintage-macs+unsubscribe@ > googlegroups.com > For more options, visit this group at http://groups.google.com/ > group/vintage-macs > > Support for older Macs: http://lowendmac.com/services/ > --- > You received this message because you are subscribed to the Google Groups > "Vintage Macs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to vintage-macs+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- -- ----- 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 vintage-macs@googlegroups.com To leave this group, send email to vintage-macs+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/ --- You received this message because you are subscribed to the Google Groups "Vintage Macs" group. To unsubscribe from this group and stop receiving emails from it, send an email to vintage-macs+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
