Servo tracks on SMD disk

Hi Tony, You're speaking of the individuality of a DOG! A cat makes miau! :-) No crash. But I have to admit that I got the drive crashed a few years ago. After cleaning and using another pack it worked. I had 3 packs for it. At some point in history I got a bunch of packs. They were used with a somewhat dubious Nova clone system (DDC or DCC). They never really worked fine. A few months ago now the drive completely broke down: After having successfully used the machine for several hours and pausing for another few weeks, I ran into disaster: A mechanical buffer at the back of the head slide had changed to a sticky liquid and blocked the whole mechanism. That resulted in the heads staying on disk while the drive did an urgency spindown. I disassembled the whole thing and cleaned away the mess as good as possible. I did not touch the head alignment. The heads stayed bolted to their slide and were taken aside as a whole block. I also took care for the heads not getting in contact. This week I reassembled the drive and tried it out. The cartridge that was in the drive during the disaster was far gone and runs with "pre-crash" noise. I realized that I had only the dubious packs. Some of them as I found out yesterday can be formatted by the Emulex SC02 controller's low level format routine, some stop shortly before the end (as I explained before). When I then try to use them, I can run "INIT/BADBLOCKS" under RT11 which says no bad blocks. Then when copying data in, I get write errors and bad blocks. Number increases. They stay and are in the system area most of the time. So I cannot use the packs :-( The whole procedure can be repeated using the low-level formatting routine and then RT11 INIT. That leads to the idea that there's something wrong about the data as well. Exactly. Sorry, meant "inner", of course! I was tiredly writing in foreign English... Yes. But... Sorry for saying that: That machine has a very very low priority in my project queue as it's something from the 80s. I currently have enough older stuff to repair (RK05s, TU56s, PDP8/I, PDP8/Ls, Honeywell DDP-516 and H316 reconfiguration and testing, etc.). I just wanted to get it either working and back in the rack or out of the window (i.e. give it to someone else, NOT trashing it!). Speed might be worth a thought: - If running too slow, servo and data head read levels might be low. I doubt that it's that but this could serve as an explanation for servo AND data problems. - If running too fast, bad things at the end of sectors can happen. And the write current could be insufficient for a good write. Servo should be not affected by this. I esteem that both possibilities need a great variation in speed. So I assume that speed is not the problem. But I'll try to check that next time I get to the drive! I'm not 100% sure but I think to remember that the fixed and the removable disk use separate motors. At least I remember a power plug labelled "motor 2"! I'll try to. I have nothing to single step the drive. No exerciser and no pdp11 programming experience (yet, will come when I get to resurrect the 11/20). And there's that Emulex controller between the pdp and the drive. That remaps the disk afaik. I have the complete manual with schematics sitting here. BTW would it be good to scan it for Bitsavers? I could easily do that as it's a ring binder and my newly acquired scanner is hungry for paper... Good night with kind regards, Philipp