ACB.TYM@office-2.ARPA (Alan Bomberger) (05/22/85)
Before I rush out and blow money on repairs, a quick question. My 8 incher (morrow disk jockey 2) no longer unloads the head after an idle period. This used to be intermittent then would work for 5 minutes after power up and is now solid. All is well as long as I don't open the door to change disks. When I close door with a new disk the head is still loaded but the controller is confused and no longer can read until the controller is reset AND the drive is powered off and on. I did verify that the LOAD HEAD line is active from the controller but don't know if the controller is responsible for unloading the heads or is it the drive that signals not ready and then the controller unloads the heads. Don't know if the controller or drive is at fault. Any ideas. Thanks in advance.
ACB.TYM@office-2.ARPA (Alan Bomberger) (05/23/85)
Well thanks for the help. I found that the index LED was fading out and finally stopped all output. The drive will not unload the heads if the disk is not ready (weird). Also the disk stays ready once the condition was detected untill the door is opened. Apparently the LED was ok right after power but faded as it got hot. I replaced it with a high output Infrared LED from radio shack and all is well. Weird!
jellis%marlin@nosc.ARPA (John A. Ellis) (05/23/85)
Your problem is not as weird as it may seem at first. The WD179X series of disk controllers unload heads after 15 revolutions if no other command has been received. The way it counts revolutions is by counting the index pulses, which it couldn't do in this case. Also the problem with the drive staying ready even after the index holes could not be detected is a problem with the control logic on the Shugart SA800/801. We were using a power-down circuit to shut off power to the drive motors and after much work found out why our software would never detect that the drive was not ready. Shugart fixed this problem on their 850/860 series. I'm not sure that all floppy manufacturers had the same problem or not. John A. Ellis