Eudimorphodon
Veteran Member
One of my side projects lately has been coming up with ways to convert a bare Tandy 1000 HX motherboard into a working test mule for expansion boards and whatnot. It's reached the point that it was time to tackle assembling some kind of custom cable or adapter to connect a firmware-modded Gotek to use as a floppy drive. I was in the process of debating between a few different strategies when a light came on for a quick, easy, and reversible way to do it that just needs a 2x17 (or longer cut to length) long-tailed wirewrap or "stacking" 2.54 mm pitch female header and a piece of wire. (That part may be optional if your Tandy has standard power connectors available to tap or split.)
Step 1:
Pick an orientation for your header. Locate what pin will engage with pin 1 on either the motherboard or the floppy drive, and using a pair of needlenose pliers bend the first six pins (technically the first one is optional, it's NC) from pin 1 and the last three pins from pin 33 on the "odd" row down horizontal. Don't cut them off yet.
Step 2:
If you want to draw 5v for your floppy from the motherboard solder a wire to any of pins 3-11. Pins 29-33 will have 12v on them, tap that if you need it. (A Gotek doesn't need it, a real FD probably will.) The other pins on the odd side, 13-27, are grounds. I checked on the Gotek and the ground lines on the floppy power plug are common with the ground pins on the signal plug, so for that at least there's no need for a ground wire to go to the power connector.
How long you make these wires depends on where you intend to put this header. If you're putting a Gotek on the same chain as an original Tandy 3.5" drive you can put the header directly on the drive's signal pins; then you'll only need an inch or two of wire to loop over to the 5v line on the power plug. If instead you'd rather convert all the cabling in the machine to be safe for normal drives then you might want to stick the header on the motherboard's connector; in that case you'll want power wires long enough to run to your drive bays.
(I don't have a complete Tandy with this sort of wiring around to know if there's actually clearance to fit it in the motherboard plug. That's how I did it on my Frankenstein machine because I have no Tandy floppy drives; if I add a physical floppy to the internal chain along with the Gotek it'll be a standard one so I might as well keep the power off the signal cable in the first place.)
After this you'll probably want to cut or tape off any power pins you're not using to avoid the risk of shorting them.
Step 3:
Solder a connector to your power wire that will engage with the power plug pins. Again, for the Gotek I only needed to populate a single wire so I just used one pin of the chunk of stacking connector I cut off when I trimmed a 2x20 down to 2x17, but if you have the correct locking plug lying around by all means use it.
Step 4:
Plug everything together, making *sure* you get the pin 1 orientation correct. Here's a few pictures:
First smoke test of the idea:
Close-up of the modded header in the motherboard connector. I'm drawing the power for the Gotek with that test clip:
The complete mess after I soldered in the power wire. Again, I'm using the "long wire" configuration because the header's going in the motherboard, not on the drive. (Also note I'm using this really long "universal" floppy cable here, and because of the orientation of things I decided to plug the "B-drive" connector into the motherboard and use the "motherboard" connector for the drive. It doesn't matter because the Tandy uses Shugart wiring/jumpering instead of using the twisted cable for A:
Up and working. I went ahead and installed an OLED into the Gotek while I had the soldering iron out for the power cable.
Step 1:
Pick an orientation for your header. Locate what pin will engage with pin 1 on either the motherboard or the floppy drive, and using a pair of needlenose pliers bend the first six pins (technically the first one is optional, it's NC) from pin 1 and the last three pins from pin 33 on the "odd" row down horizontal. Don't cut them off yet.
Step 2:
If you want to draw 5v for your floppy from the motherboard solder a wire to any of pins 3-11. Pins 29-33 will have 12v on them, tap that if you need it. (A Gotek doesn't need it, a real FD probably will.) The other pins on the odd side, 13-27, are grounds. I checked on the Gotek and the ground lines on the floppy power plug are common with the ground pins on the signal plug, so for that at least there's no need for a ground wire to go to the power connector.
How long you make these wires depends on where you intend to put this header. If you're putting a Gotek on the same chain as an original Tandy 3.5" drive you can put the header directly on the drive's signal pins; then you'll only need an inch or two of wire to loop over to the 5v line on the power plug. If instead you'd rather convert all the cabling in the machine to be safe for normal drives then you might want to stick the header on the motherboard's connector; in that case you'll want power wires long enough to run to your drive bays.
(I don't have a complete Tandy with this sort of wiring around to know if there's actually clearance to fit it in the motherboard plug. That's how I did it on my Frankenstein machine because I have no Tandy floppy drives; if I add a physical floppy to the internal chain along with the Gotek it'll be a standard one so I might as well keep the power off the signal cable in the first place.)
After this you'll probably want to cut or tape off any power pins you're not using to avoid the risk of shorting them.
Step 3:
Solder a connector to your power wire that will engage with the power plug pins. Again, for the Gotek I only needed to populate a single wire so I just used one pin of the chunk of stacking connector I cut off when I trimmed a 2x20 down to 2x17, but if you have the correct locking plug lying around by all means use it.
Step 4:
Plug everything together, making *sure* you get the pin 1 orientation correct. Here's a few pictures:
First smoke test of the idea:
Close-up of the modded header in the motherboard connector. I'm drawing the power for the Gotek with that test clip:
The complete mess after I soldered in the power wire. Again, I'm using the "long wire" configuration because the header's going in the motherboard, not on the drive. (Also note I'm using this really long "universal" floppy cable here, and because of the orientation of things I decided to plug the "B-drive" connector into the motherboard and use the "motherboard" connector for the drive. It doesn't matter because the Tandy uses Shugart wiring/jumpering instead of using the twisted cable for A:
Up and working. I went ahead and installed an OLED into the Gotek while I had the soldering iron out for the power cable.
Last edited: