Friday, June 5, 2015

Studying how to set up escapement and carrier return cords on 1053, plus newly acquired Pertec cartridge disk drive


I need to think about and research how the escapement cord is affixed to the escapement drum - the knot wedged in a slot just popped free when the carrier slammed into the far left end. This could be caused by the spring I stuck on the torque limiter, it may be caused by the way I installed and wound the cords on the drum, or it could be a misadjusted or malfunctioning part in the air piston that decelerates the carrier at the end of a return.


I found a recycler offering a Pertec 4246 unit which had a single platter top loading cartridge (5440 style) which is an IBM repackaging of similar technology to the 2315 cartridges used in the 1130. There are two 14" platters, one fixed inside the bottom of the spindle and the other contained in the cartridge.

I figured that the drive may have disk heads I could use to restore the 2310 compatible Diablo unit I own. When I got it home, I found it had two new-old-stock 5440 cartridges in boxes inside the cabinet.

I hadn't opened up the unit yet to check the condition of the heads, but with a fixed plus a removable platter, there are four heads and I only need 1-2 good ones. Late in the early evening, I did open it all up. I found I had a good removable cartridge inside, plus the two NOS onces. The disk surface on the removable pack and the fixed platter underneath were scratch free, although they had a coat of dust that must be removed.

Inside, I looked at the disk heads in situ, which doesn't give me quite the access I might have if I removed them, but decent enough to see that there are no visible signs of scapes or smears of brown oxide. This is very promising.

The logic comes up enough to indicate the write protect status (using independent rocker switches for the lower and upper platters) and that it was in 'safe' mode - absence of recognized error conditions. However, no fans were spinning, no blower going and no spindle rotation. This may be a safety feature when the interface is not properly terminated; my two ribbon cables were hanging loose.

The biggest issue is that I have no documentation on the drives, no schematics, and no docs on the interface. A quick peek at bitsavers and a few google searches came up with nothing. 


  1. Did you ask Al directly?If he has anything not yet scanned he could probably move it up on the list.

  2. The documentation lists methods but not in full detail. For example, nothing shows what proper positioning should look - should the drum have 200 degrees (partial turn) on the escapement drum when the carrier is at a certain left point? How taut should the cords be? FEs learned this by experience, not from the documentation. So must I.