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09.002 How do I add an external speed adjustment to my Disk ][?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
09.002 How do I add an external speed adjustment to my Disk ][?
Reference: FAQs Resource file R006SPDKNOB.GIF
Adding a Speed Control Knob to your Disk ][ Drive
This article tells how to move speed adjustment from the Disk ]['s dark
interior to a handy front-panel location and how to "tune" the drive for
optimal performance.
One drive-test software vendor states that Disk ][ is good for about 500
hours of normal use between speed adjustments-- not exactly a strong argument
for placing the control on the front panel! On the other hand many of today's
Disk ][ owners are interested in applications which go beyond "normal use".
Some utilities (e.g. DiversiCopy II) report rotational speed during
ongoing applications; so, relocating the speed adjuster to the front panel is
especially helpful. Similarly, users who want to back up their old, copy-
protected wares know that ready access to speed control is essential.
Finally, there is no question that, whatever your applications, periodic
speed trimming will be required. When it is, you'll be very glad your Disk ]
[ has a front panel Speed Knob!
Adding Speed Knob
To install Speed Knob you will need a good quality, linear taper 5k Ohm
potentiometer, some wires, and a knob with a pointer mark or some other way to
show position (e.g. a ring of numbers). Most of the work, really, consists of
opening the drive and drilling a hole. There is no need to disconnect the drive
from the controller card.
1. Remove the 4 bottom bolts and slip off the case. Unscrew the 4 bottom bolts
holding the drive to the case bottom, and unplug the main ribbon cable. The
drive can now be moved to your work area.
2. Drill a hole properly sized and centered for mounting your 5k Ohm pot in the
upper right front panel.
3. Place the drive on its face and unscrew the 2 bolts which hold the small
daughter board to the drive. (Be ready to catch loose spacers, washers, etc..)
4. Turn the small board over to the bottom side. Locate and cut the traces
going to the mini-pot speed adjuster as shown in pic R006SPDKNOB.GIF.
5. Cut three wires, White, Gray, Black, long enough to reach from the board to
the front panel. Connect these to your 5k Ohm pot and to the small circuit
board as shown in pic R006SPDKNOB.GIF. (In case you cannot view the pic, what
you're doing is substituting the new pot for the mini-pot. )
6. Re-mount the daughter board. Mount the 5k Ohm pot. Install knob.
7. Bring the drive back to the computer. Slide it onto the case bottom plate,
reconnect main ribbon cable, replace bottom bolts, slide on and re-fasten case
top.
You can use Copy II Plus, XPS, APEX, or one of several other utilities to
set speed (see next question). A good starting adjustment will be near the
center of Speed Knob's range. Once speed is adjusted, you can loosen and re-set
the knob so that its position indicates a "correct" speed setting.
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