EXCHANGE THE DRIVE IN THE SX64 WITH A STAND-ALONE 1541 MECHANISM 9-22-04.
REPLACING THE DRIVE IN THE COMMODORE SX WITH A STAND-ALONE 1541 MECHANISM latest additions and/or corrections 9-22-04 > I want to swap the drive from my SX64 and a 1541 stand alone. > When I took the drive out of the 1541 it had three white wire > connectors and one black. On the SX all the wires go into one white > connector and one black. What is the best way to fix this small > problem? Simple question, complicated answer. ;-) It will take a bit of work to fit that replacement drive because the connectors -are- different although the drives themselves are essentially the same. Fortunately, the color coding of the wires is the same (with some exceptions, discussed later). Swapping a stand-alone drive mechanism into an SX involves changing the three connectors on that drive into one 15 pin plug that fits the FDD board connector. You can use the existing 15 pin plug from either drive as your replacement (see precautions later in this article). The black plug is for the read/write head and it needs to be lengthened to reach the connector on the PC board. You can cut the one from the old drive and splice it onto the existing one when that plug is cut off. The four wires inside the shield are color coded and must be spliced and insulated from each other and from any metal around them. Note that one pin (2) on that black plug is not used and thay provides a "key" for proper orientation. The "missing" socket pin should line up with the "missing" wire in the plug. If you carefully examine each white plug, you will see a number 1 on one end. That identifies pin 1 and is how you know which way to wire up and install the new plug. Mark each connector and board with a magic marker or felt tip pen to identify pin one before you start rewiring. Another important bit of information: the white plug on the SX and the white plug on a stand alone drive look identical until you turn them over. Notice that the only way the replacement will fit on the SX connector is if it's reversed!!! So, if you're going to use the plug from the stand-alone 1541, all pins will have to be removed and refitted so that plug will fit the socket and each wire is oriented to the correct position. It would be easier to just reuse the large white connector off the SX drive. Although it's quite a bit of work, I would replace an SX drive if the existing one could not be easily repaired (bad R/W head, for example). I took my own SX and three different stand-alone drives apart to verify this information. That said, there are always unforseen problems with any first-time project. I don't usually make disclaimers but I feel I must in this case. Some of the wires are the same color, so it's easy to make a mistake when rewiring the connectors. That's why I always rewire plugs one pin at a time. I make notes as I pull things apart and label each item. Rather than cut and solder, it's easiest to remove each wire from the three white connectors by releasing them and pulling them out. The retainers can be seen if you look closely at the openings in one side of the connectors. Each pin has a tab on one side that needs to be pushed flat with a pointed tool so the pin can be pulled out by tugging gently on the wire. Don't use too much force or you'll bend the pins. To reinstall those pins, the tab will have to be pulled back up a little so the pin will snap into the new socket and not fall out. I prefer to use a small jewelers screwdriver (but a large straight pin works fine too) to help slide the pins out of the connectors. The same tool can be used to force the pins tabs back open by pushing the point of the pin into the void under the tab. Too much bending back and forth will break that tab, by the way... and the' pin will not stay in the connector. If that happens, the pin will have to be replaced (another one soldered onto the wire). You will run into a few problems if you try to install a Newtronics drive in the SX. It will work, but there are mechanical differences between the existing ALPS drive and the later Newtronics mechanisms that make it a less than optimal match. Notice that the Newtronics twist-down door latch sticks out about 3/8" further that the ALPS push-down door. The Newtronics latch will hit the keys when the keyboard is fitted onto the front of the computer for storage or transport, but it looks like there is enough clearance. The only way to know for sure is to try it. A more difficult problem with the Newtronics mechanism is the metal plates that stick out on the sides of the case and prevent the SX mounting bracket from being easily installed. Compare the drives side by side to see the difference. One fix is to grind off the excess metal with a file (looks like a real grunt). If you add shims or washers to make the drive fit the SX plate, it will be difficult or impossible to remount that plate correctly in the computer. Not all the screws will line up with the base underneath unless you redrill the plate. Because of those problems, I would go for the ALPS drive as a replacement. They are more reliable in an SX because they don't run as hot as in a stand-alone 1541. You will need the pinouts of the two types of drives. Note that the same wire colors are used more than once. That makes it necessary to trace each one back and find out where it originates so you know each one is re-wired correctly. To make tracing easier, you will probably want to cut the wire ties and free the wires from the bundles. Be careful you don't nick or cut any wires! Retie the wire bundles with string when you're finished. Note: NC below means no connection. 1541 STAND-ALONE SX 1541 INTERNAL DRIVE P5 (SPINDLE MOTOR) P21 (SINGLE WHITE CONNECTOR) 1 BLACK, common 13 2 BROWN, +12V 12 3 ORANGE, motor on/off 11 P6 (SENSORS) 1 YELLOW, wp ground 15 (note: the SX wire is blue) 2 BROWN, wp LED + 14 3 NC 4 NC 5 NC 6 NC 7 NC 8 RED, activity LED anode 8 9 BLK, activity LED cath 7 10 NC 11 NC 12 ORANGE, wp sensor + 4 13 GREEN, wp sensor ground 3 14 NC 15 NC P7 (STEPPER MOTOR) 1 RED, +12V 9 2 RED, +12V 10 3 YELLOW, step 2 6 4 ORANGE, step 0 5 5 BLACK, step 1 2 6 BROWN, step 3 1 Ray Carlsen CET Carlsen Electronics... a leader in trailing-edge technology.