jeffj@sfsup.UUCP (02/07/87)
I never pulled the 'emergency pull' switch for fear of crashing the disks. As it turns out, he heads are loaded by a solenoid, so turning the power off raises the heads. I'm not sure if they'd retract properly when powering up again (to load properly on the outer tracks). Professor Costello (of The Cooper Union), however, always wondered what happens, so he pulled it. The power went off to everything. You see, the switch turns off the main power relay, and turns everything off without regard to the sequencing. There is a collar on the knob shaft, behind the panel. There is a spring resting on the collar, like this side view: panel | | [[]] [] [[]] switch ========[]===========[[]] [] [[]] / | [[]] / / spring The spring snaps behind the collar, preventing you from pushing the button back in. I know because I have the button and panel piece right here. (Yup, I have pieces of the 1130 all over my home and office). This is the same on the system 3. Just a poke with a screwdriver gets it reset. The spring can be bent to never interfere again. In <3378@milano.UUCP>, John Fehr says that "after 15 years, the plastic becomes a bit brittle". I guess that the knobs were changed to plastic at some time. Mine is all metal. The Amdahl's are metal too. In <706@argus.UUCP>, Art Marriott says that the IBM CE had to reset the switch. Yup, that's the function of the spring and collar. I guess that the power sequencing was important enough that maybe things would lock up or get damaged (like the disks?). Or it was a gimmick to get extra service calls (if you're desperate enough to pull the Emergency Off switch instead of just turning it off, you deserve to be punished). Jeffrey 'paper based lifeform' Skot {ihnp4 | allegra | cbosgd} attunix ! jeffj P.S. I had two of the hole punches used for the 1132 printer's carriage control tape (remember the 12 channel tapes?). I remember places like INMAC charging around $200 for them. After nobody wanted to buy them, I donated them to The Smithsonian. They truly are "The Nation's Attic".
toma@tekgvs.UUCP (02/09/87)
In article <1092@sfsup.UUCP> jeffj@sfsup.UUCP (J.S.Jonas) writes: >I never pulled the 'emergency pull' switch for fear of crashing the disks. ... >Professor Costello (of The Cooper Union), however, always wondered what happens, >so he pulled it. The power went off to everything. >You see, the switch turns off the main power relay, >and turns everything off without regard to the sequencing. ... >In <706@argus.UUCP>, Art Marriott says that the IBM CE had to reset the switch. >Yup, that's the function of the spring and collar. I guess that the power >sequencing was important enough that maybe things would lock up or get >damaged (like the disks?). Or it was a gimmick to get extra service >calls (if you're desperate enough to pull the Emergency Off switch >instead of just turning it off, you deserve to be punished). > The power-down sequence for these old machines left the cooling fans on for a long period to remove the residual heat. Pulling the Emergency Off switch cuts all the power, even the fans, causing the temperature in the cabinets to *rise*. This could cause damage to sensitive components such as memory cores (or drums, etc). The switch would lock up forcing the service call and the (more important) running of diagnostics to insure no damage was caused. To quote from IBM Form 22-6060-1, IBM 650 Manual of Operation, 1953 (portions marked with "*" were italisized in the manual): Power-Off Button When this button is depressed, the following sequence of events occurs: 1. DC power is turned off. 2. AC power (except that supplied to the blower motors) is turned off. 3. The blower motors are turned off after a five minute delay. DC-Off Button ...Depressing the DC-OFF button will cause all DC power to be turned off and the ready light will go out. The DC-OFF button has no effect on the AC power. When this button is used, the machine can be shut down for comparitively short periods (e.g. an hour) without necessitating cooling off and reheating the electronic tubes in the machine. Master Power Switch The master power switch is for *emergency use only*. When this switch is depressed [sorry, predates "Emergency PULL"], all power, including that to the blower motors, is removed from the machine *immediately*. The depression of this switch also activates a locking device which makes it *impossible* for the operator to turn the machine back on. A customer engineer *must* be called in order to get the machine back in operation. Tom Almy Tektronix, Inc. tektronix!tekgvs!toma
warren@pluto.UUCP (02/10/87)
At Yeshiva University, there once was an 1130 (heard it caught fire) and we were told that exceedingly terrible things would happen if you pulled the Emergency Pull, as if the CE would have to come in and do some very involved operation to fix it (rethread the wires in the core? :-) ). After it somehow got pulled, the CE showed us how to pop it back out and we used it whenever we didn't want people on the system. --