Hi Michael, Browsing the link you attached reminds me of one problem I came across some time ago... The drive seems to complain about the missing speed signal. How is the speed signal generated? Is there still an opto coupler under the drive assembly detecting the sector impulses from a crown like mechanic coupled with the spindle? It is perhaps worth to check the LED / photo transistor for dust. When done verify that a proper signal is generated and transmitted to the disk controller assembly. Hope it will help, please keep us updated about your progress. Bernhard Wulf -----Original Message----- From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Michael Thompson Sent: 31 January 2011 09:45 To: cctech at classiccmp.org Subject: RA81 Disks Will Not Spin up at the RICM. So far we have tried 5 RA81 and 1 RA80 disk at the RICM. They all have the same symptom, when you push the RUN button. The drive starts to spin up for just a few seconds, then stops and lights the FAULT light. We ran diags on one of the drives. The details are here: https://sites.google.com/site/ricmwarehouse/Home/equipment/dec-pdp-1144/ pdp-11-44-restoration We made sure that the heads were unlocked and the drive belt was engauged. Debug suggestions would be appreciated. -- Michael Thompson