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Tandy 1000 RL floppy drive replacement

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geiger9

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Feb 10, 2022
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Hey everyone,

I just bought my childhood computer - a Tandy 1000 RL but the floppy drive is dead. I have cleaned the heads and lubed the rods but it's still dead. I was reading on the oldskool.org website that only these low density floppy drives will work in my RL:

Sony MFD-63W-70D
Sony MP-F11W-71
Sony MP-F11W-72
Sony MP-F11W-72D
Sony MP-F63W-01D
Teac FD235-136U
Teac FD235F-105U
Teac FD235F-106U

Are these the only models that will work because they have the power and data coming through one cable? Will these only work because they are low density? Is it both things?

Is there any way to use a high density floppy drive with my RL?

Can I use this adapter from https://www.tindie.com/products/cyberneticsys/tandy-1000-internal-35-fdd-adapter/ and use any old low density floppy drive? Or can I use a high density one with some modification to the computer?

And yes, I know there are options besides using a floppy but I want to use floppies.
 
All answers here

Tandy 1000-series FAQ

Frequently asked questions file for the Tandy 1000-series computers.
www.oldskool.org

Although it would look ugly and stupid
if you mod / repin one end of the floppy cable you can make an adapter from Tandy to a bog standard floppy drive, you won’t have the cool blue button though.

If you want high density as far as I know you will need a gsi (or similar) floppy controller with bios, the Tandy may not want to have a secondary controller and likely won’t disable the OEM but never tried when I had an RL.

If the GSI would work you could then likely use both standard IDE and Floppy drives )my GSI would run its own bios for both floppy and HD(
 
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geiger9 said:
Are these the only models that will work because they have the power and data coming through one cable? Will these only work because they are low density? Is it both things?
Click to expand...

The big deal is the power lines. Those will let the magic smoke out of any floppy drive that follows the standard of tying all the odd-number pins of the connector to ground. (And possibly take the computer with it.) FWIW, an alternate way of defanging the power problem (vs an adapter board or cutting up the cable) is to just slap a stacking header in between the cable and the socket at either end; here's how I did it with an HX motherboard, at the motherboard end. The header is a cut-down 40 pin stacker intended for Raspberry Pi applications and cost about $2.

High-density 3.5" floppy drives will run on low-density controllers just fine. You'll only be able to use low-density disks, but considering how actual low-density drives are a little thin on the ground anymore it's still nice you can sub them. The other problem, though, specifically with Tandy machines, is that many newer floppy drives don't have drive select jumpers anymore. The PC wiring standard is that all drives have their selects set for "Drive B", and for drive A there's a twist in the cable that flips over the select/motor lines so the B-selected drive comes on when the controller activates the "A" select on the motherboard end. If you want to use a drive that doesn't have select jumpers with a Tandy 1000 as drive A then you have more work to do, like hacking/soldering the drive's PCB or rearranging some wires in the cable.
 
I can confirm that you can use a high-density drive in a 1000RL/SL/TL; it will only function as a 720K drive, but will work fine.

And I doubt the 1000RL's 25-watt power supply has anywhere near enough current to smoke a floppy drive. The overload protection circuitry will kick in and it'll either quickly shut down or refuse to power on at all.
 
vwestlife said:
And I doubt the 1000RL's 25-watt power supply has anywhere near enough current to smoke a floppy drive. The overload protection circuitry will kick in and it'll either quickly shut down or refuse to power on at all.
Click to expand...

It's still not an experiment I would recommend anyone try; I vaguely remember a YouTuber smoking a Gotek with a Tandy 1000HX, and that machine has a similarly feeble power supply. You're right that with a direct path between ground and the rails it definitely should trigger the short protection, but torturing thirty year old electronics like that on purpose seems like maybe not the brightest idea in the world. So far as it goes smoking the power supply would be a bigger deal than killing the floppy drive.
 
Thank you to everyone so far with your advice this is exactly the kind of info that I was looking for.
Eudimorphodon said:
High-density 3.5" floppy drives will run on low-density controllers just fine. You'll only be able to use low-density disks, but considering how actual low-density drives are a little thin on the ground anymore it's still nice you can sub them. The other problem, though, specifically with Tandy machines, is that many newer floppy drives don't have drive select jumpers anymore. The PC wiring standard is that all drives have their selects set for "Drive B", and for drive A there's a twist in the cable that flips over the select/motor lines so the B-selected drive comes on when the controller activates the "A" select on the motherboard end. If you want to use a drive that doesn't have select jumpers with a Tandy 1000 as drive A then you have more work to do, like hacking/soldering the drive's PCB or rearranging some wires in the cable.
Click to expand...
So if I connected a newer floppy drive without drive select jumpers, would I only be slightly inconvenienced because I have to type b: instead of a: at a DOS prompt? Or are there other issues?

Can anyone recommend me a floppy drive solution here? Has anyone had success using that adapter I mentioned in my OP and using any old disk drive? Did it fit with the bezel or did you have to hack up the bezel to make it fit?
 
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geiger9 said:
So if I connected a newer floppy drive without drive select jumpers, would I only be slightly inconvenienced because I have to type b: instead of a: at a DOS prompt? Or are there other issues?
Click to expand...
Tandys use the original Shugart drive interface which uses a flat cable with the A: drive set to DS0 and the B: drive set to DS1. If you use a drive which is hard-wired to DS1 (as most newer 3.5" drives are), it will be B:, but I don't know how the 1000RL would deal with not having an A: drive -- it might get hung up trying to look for a drive that doesn't exist.

And if you try to replace the cable with one that has the twist in it, that won't work. I've tried, but no amount of fiddling with jumper settings will get a floppy drive to work with a twisted cable on a Tandy.
 
vwestlife said:
And if you try to replace the cable with one that has the twist in it, that won't work. I've tried, but no amount of fiddling with jumper settings will get a floppy drive to work with a twisted cable on a Tandy.
Click to expand...

I haven't actually tried this so, well, assume this suggestion will melt your computer until proven otherwise, but if you're willing to make/modify your own cable I think putting a twist in it so pins 10 and 12 are swapped will do the needful.

(PC twisted cables won't work because the Tandy wiring scheme uses a common "Motor On" signal that's no longer connected properly after the twist. Just swapping lines 10 and 12 should put the "A" drive select from the computer on the "B"-jumpered drive's select while preserving Motor On on pin 16.)
 
You just need a matching button, but nobody's come forward with a suitable 3d-printable button. If your replacement drive is the same brand the button should transfer over.
 
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