On Mon, Jul 24, 2017 at 6:12 AM, Fritz Mueller via cctalk <cctalk@classiccmp.org> wrote:
> "OMG, are you nuts, don't take the heads out, you'll never get them > aligned," > > or is it: > > "Meh, RK05 alignment is not really that tough, and you would be better off > making sure your heads are thoroughly clean and intact." > > Any advice appreciated! I've done it a couple of times. The worst part is that it is somewhat nerve-wracking when you have put the expensive, hard to find, new heads in, load the rare and hard to find alignment pack and are about the load the heads praying to the patron saint of classic computing [St Chad of Hackforth [1] of course] that the heads won't crash. Basically, you connect a 'scope to the outputs of the read amplfier, trigger off the index pulse, move the heads to the right cylinder (just toggle in a few values on the PDP11 front panel) and adjust so that the catseye pattern is even. There are 2 allen setscrews for each head. One locks the head in postion, the other forces the head out towards the spindle. So what you do is slacken the latter off, put the head in as far as it will go, clamp it with the first screw, load the alignment pack then undo the locking screw slightly and screw in the pushing screw until the catseyes look right. If you overshoot you have to unload the heads, loosen the pusher screw, push the head in and repeat. ALWAYS have the head locked to the carriage when loading or unloading. Head alignment is an interchangeability adjustment. An RK05 with misaligned heads will format a blank pack and write/read it with no problems. But that pack won't work in other drives. To get it right you need the alignment pack (incidentally neither of my RK05 alignement disks are red, they are the normal white housings). Now there is a cheat that works some of the time. It goes like this. Before removing the heads, screw in the pusher screws until they are contacting the back of the head mounitng pin. Lock those screws with a drop of nail varnish or an extra nut. Then loosen the locking screws and pull the heads out. When you come to reinsert them, just put them in until they contact the pusher screws and lock them. They are in essentially the same position and may well read the old packs fine. It's up to you if you try it. [1] St Chad was AFAIK a real saint. Hackforth is a village in Yorkshire, England. I don't think there's any connection but the names seem right for classic computing. -tony
