Ken Shirriff on Twitter: "We finally fixed the 1960's IBM mag tape drive @ComputerHistory. Slack tape is held in vacuum columns, with pressure switches to sense the tape position. After probing resistor-transistor
Ken Shirriff on Twitter: "An IBM 729 tape drive holds loops of tape in vacuum columns, allowing the tape to start and stop suddenly. One of the vacuum pumps @ComputerHistory failed and
Ken Shirriff on Twitter: "Old tape drive maintenance at @ComputerHistory. We fixed the door latch on a 729 drive. Also investigated a tape drive malfunction, apparently due to a flaky circuit breaker.
![Ken Shirriff on Twitter: "IBM 729 tape drive repair today @ComputerHistory. The tape moves in the vacuum columns, controlled by vacuum switches. Clutches spin the reels to keep enough slack tape in Ken Shirriff on Twitter: "IBM 729 tape drive repair today @ComputerHistory. The tape moves in the vacuum columns, controlled by vacuum switches. Clutches spin the reels to keep enough slack tape in](https://pbs.twimg.com/ext_tw_video_thumb/1509329322955268098/pu/img/xstwD1cvcY5ZeANd.jpg)