8" drive supply disparities (was Re: WTB: 8" floppy)

Though I've heard of them, I've never seen an 8" drive that operated from the Vcc supply alone, nor have I seen any printed allusion to them. Back in the days when the 8" drive was in full usage, there were few drives available that didn't use the three available supplies. In the years when smaller drives were becoming popular, manufacturers of 8" drives figured out a few things that might be impacting their reduced 8" drive sales. These included the use of several supply voltage requirements, but that was partially dealt with by using single-supply amplifiers, and the noise of the AC motors, which was dealt with by using DC motors. However, the sheer mass of an 8" drive mandated a cost that was easily beaten in the marketplace by the smaller drives, and, no matter how well the 8" drives did with reduction of power supply demands and in noise, once the smaller drives were able to produce the same capacity, not to mention that the evolution of the hard drives of small form factors were able to offset the capacity demand somewhat, the fate of the 8" drive was sealed, even if its capacity could be doubled or tripled, since the combination of floppy and hard disks was now a reality, and large capacity was no longer of such large interest. 8" drives with which I've had contact, with a VERY few very old exceptions, notably PerSci, have always used the Shugart-defined 6-pin connector with which we all became familiar if we used 8" drives in the '70's. If the drive required a supply, it was normally provided by the PSU that one commonly associated with 8" drive pacakges, e.g. the PowerOne CP206 and others of that ilk. If a drive didn't need the Vee supply, it didn't matter that it was there. If it did need that supply and your particular supply didn't provide the correct voltage, an on-board regulator on the drive could be installed to handle that if it wasn't already there. Moreover, many supplies were adjustable, either by tweaking a pot or by changing a resistor (since they nearly all used the uA/LM 723 regulator, which worked in that way. If you simply hooked up a supply to a drive without first verifying that the Vee supply was properly handled, one might say you got what you deserved, however. Aside from the Vee issue, which only occurred in a very few cases wherein there was no regulator on the drive AND the supply was incorrectly set up, there was little likelihood of damage to the drive or supply. The drive was unlikely to work if Vee was -12 volts, however, if the drive was set up to use -5. Permanent damage to the drive was unlikely however, since the devices involved were of a type normally used with a bipolar 15-volt supply. While the biasing necessary to make these work at bipolar 5 volts wouldn't work if the two supplies were unequal, serious or permanent damage was unlikely. Dick ----- Original Message ----- From: "Tony Duell" <ard(a)p850ug1.demon.co.uk> To: <classiccmp(a)classiccmp.org> Sent: Saturday, June 30, 2001 12:27 PM Subject: Re: WTB: 8" floppy board If possibly