>> Now I've never used a RL02 drive on 50Hz power, but I'm 99% certain that
>> the motor speed in a RL02 is determined by a servo loop, and thus
>> not locked to a multiple of the AC frequency.
>>
>> I think the fan in a 50Hz RL02 will run a bit slower, but I don't think
>> this will hurt anything.
>Motor speed is controled by line mains freq. I think the 50hz unit has
>a differnt spindle size. I havent looked under one in 15 years.
What you say certainly describes the RK05, lots of 8" floppy drives
with AC-drive motors and belts, and many other 14" disk drives,
but I'm now 99.44% certain that there's a servo loop for motor speed
regulation in a RL02 and that it's not tied to having a mathematical
relationship of pulley sizes or the AC line frequency.
In fact, my "RL01/RL02 Disk Drive Maintenance Course" textbook says:
The circuits controlling the drive motor in line are
located on two modules. The drive logic module
decodes the speed of the rotating spindle and sends
the signals to the AC servo module which controls
the drive motor's duty cycle.
The disk speed control portion of the DLM monitors
the sector pulse that is created from the reluctance
pick-up and shaped by the circults on page DL6. This
shaped sector pulse, called sector detect, and the
clock from the interface logic are used by the
counting logic to determine how much time is elapsing
between sector pulses. The result is a
signal called Control Speed-up, which is sensed by
the AC servo module. When active, it increases the
duty cycle of the drive motor from 20% to 60%,
speeding up the cartridge. If the disk is within
the speed limits., Control Speed-up is negated, allowing
the drive motor to run at a 20% duty cycle.
This indicates that the master clock setting the drive rotation rate
comes from the interface board in the Q-bus/Unibus/Omnibus (I believe
this is in turn derived from a crystal oscillator), and that
it is not directly tied to the AC line frequency. Indeed, if you
put a not-RL01 or not-RL02 pack in a RL drive and try to spin it up,
the fact that the sector gaps aren't present in the same number means
that it'll spin up to a different speed than if you have a real RL pack
in the drive.
There may be a separate "50Hz" RL drive variant, but I've not seen any
indication of its existence here in North America, in parts lists,
user's manauls, or in maintenance guides. I'm sure some of our
more international members will have better information than I do.
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Received on Fri Oct 15 1999 - 11:09:16 BST