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Trying to get a 3.5" floppy to give me Drive 0 on a Color Computer 3

axim

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Jan 29, 2023
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I can build a 3.5" that runs on drive 1 all day long and it works great on my FD-500, FD-501 and FD-502. With pin changes. However, I can only ever achieve Drive 1 , most software wants Drive 0. So I end up paring the drives with a classic 5.25 drive as Drive 0 and a 3.5 with Drive 1.
I have messed with soldering the DS0 and DS1 to try and get the floppy to Drive0. I have even flipped the ribbon cable 12,13,14 . No luck.. Is anyone making an adapter that can give me Drive 0 on 3.5 floppy. I am willing to purchase quite a few from you if they work.

Thanks
 
I have tried with the twist and without the twist. The twist that I am using is flipping 12-14. I will check you link. I am going to try and check my soldering on the drive to make sure it is correct.
 
Is the drive set to DS0? If so, then try isolating pin 34. I remember having to do that years ago for some weird reason on an Epson 720kb drive. If you still have issues, I have an aftermarket pack around here that supports 1.44 drives as well. Its a J&M controller with JDOS, which are pretty rare.
 
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I can build a 3.5" that runs on drive 1 all day long and it works great on my FD-500, FD-501 and FD-502. With pin changes. However, I can only ever achieve Drive 1 , most software wants Drive 0. So I end up paring the drives with a classic 5.25 drive as Drive 0 and a 3.5 with Drive 1.
I have messed with soldering the DS0 and DS1 to try and get the floppy to Drive0. I have even flipped the ribbon cable 12,13,14 . No luck.. Is anyone making an adapter that can give me Drive 0 on 3.5 floppy. I am willing to purchase quite a few from you if they work.

Thanks
Since your 3.5" drive works perfectly as "Drive 1" all you need is a way to fool the drive it is "Drive 0" by routing just the DS1 input on the drive (leaving all other signal connections as-is) to the DS0 connection on the interface cable. The problem with using a PC drive cable with a "flip" in it is that the "flip" changes the connection of both the "drive select" and "motor on" signals, whereas you need to change the connection of only the "drive select" signal.

Use one of these adapters:

On that board, DS0-DS4 are specifically identified for those who need to redirect the cable DS0 line to the DS1 input of the drive, by cutting the adapter board trace leading from card edge connector pin 12 (DS1) and routing that trace to pin 10 (DS0) instead by soldering a short jumper. This leaves the connection to pin 16 (motor on) untouched, following the conventional definition used by 5.25" drives. You will need to use a floppy drive cable that has two card edge connectors on it, and both connectors should be straight through (no flip).

It was suggested above that pin 34 (which is alternately defined as "disk change" or "ready") might be the cause of the problem, but the fact your drive functions perfectly used as-is when functioning as "Drive 1" makes it unlikely this is the cause of your problem.
 
Also some 720kb drives have a jumper, or spot for a jumper. Could always look over the drive, usually its near the stepper motor for the heads.
 
Since your 3.5" drive works perfectly as "Drive 1" all you need is a way to fool the drive it is "Drive 0" by routing just the DS1 input on the drive (leaving all other signal connections as-is) to the DS0 connection on the interface cable. The problem with using a PC drive cable with a "flip" in it is that the "flip" changes the connection of both the "drive select" and "motor on" signals, whereas you need to change the connection of only the "drive select" signal.

Use one of these adapters:

On that board, DS0-DS4 are specifically identified for those who need to redirect the cable DS0 line to the DS1 input of the drive, by cutting the adapter board trace leading from card edge connector pin 12 (DS1) and routing that trace to pin 10 (DS0) instead by soldering a short jumper. This leaves the connection to pin 16 (motor on) untouched, following the conventional definition used by 5.25" drives. You will need to use a floppy drive cable that has two card edge connectors on it, and both connectors should be straight through (no flip).

It was suggested above that pin 34 (which is alternately defined as "disk change" or "ready") might be the cause of the problem, but the fact your drive functions perfectly used as-is when functioning as "Drive 1" makes it unlikely this is the cause of your problem.
Thanks everyone for the help. I am going to get these connectors. Looks like the way to go. I am excited to have a 3.5 x 2 for my setup.
 

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Also some 720kb drives have a jumper, or spot for a jumper. Could always look over the drive, usually its near the stepper motor for the heads.

It seems the original poster to this discussion did find the DS0 and DS1 jumper locations which (as was typical with many later drive models) are "solder jumper pads" rather than the more convenient jumper pin blocks, and tried jumping DS0 (removing DS1) without success. I'm thinking that drive model may switch the logic for the motor on signal along with the drive select logic with that single jumper change - because normally just swapping DS1 to DS0 should have worked if the drive cable twist was removed.
 
I have tried with the twist and without the twist. The twist that I am using is flipping 12-14. I will check you link. I am going to try and check my soldering on the drive to make sure it is correct.

On that board, DS0-DS4 are specifically identified for those who need to redirect the cable DS0 line to the DS1 input of the drive, by cutting the adapter board trace leading from card edge connector pin 12 (DS1) and routing that trace to pin 10 (DS0) instead by soldering a short jumper. This leaves the connection to pin 16 (motor on) untouched, following the conventional definition used by 5.25" drives. You will need to use a floppy drive cable that has two card edge connectors on it, and both connectors should be straight through (no flip).

FWIW, shouldn't you be able to accomplish this with no soldering by twisting the cable so pins 10-12 (*NOT* 12-14) are flipped? On the Shugart wiring standard DS0 is pin 10, DS1 is 12, and the common motor on is 16. Drive B on the PC is DS on 12, motor B on 16. So a flip between 10 and 12 seems like it should do all you need.

If you still have your 12-14 twisted cable lying around that should be the correct twist if you're trying to add a *third* drive on DS2...
 
FWIW, shouldn't you be able to accomplish this with no soldering by twisting the cable so pins 10-12 (*NOT* 12-14) are flipped? On the Shugart wiring standard DS0 is pin 10, DS1 is 12, and the common motor on is 16. Drive B on the PC is DS on 12, motor B on 16. So a flip between 10 and 12 seems like it should do all you need.

If you still have your 12-14 twisted cable lying around that should be the correct twist if you're trying to add a *third* drive on DS2...
Yes, that certainly is an alternative solution to the problem.
 
FWIW, shouldn't you be able to accomplish this with no soldering by twisting the cable so pins 10-12 (*NOT* 12-14) are flipped? On the Shugart wiring standard DS0 is pin 10, DS1 is 12, and the common motor on is 16. Drive B on the PC is DS on 12, motor B on 16. So a flip between 10 and 12 seems like it should do all you need.

If you still have your 12-14 twisted cable lying around that should be the correct twist if you're trying to add a *third* drive on DS2...
Yes, no soldering needed. Flipping 10 and 12 did it. Thank you. Going to assemble a 3.5 x 2 FD-502 drive set. Looking forward to trying it out. I tested this with FD-500 FD-501 FD-502, all worked. I tested 24pin and 32 pin. Both worked. I did not need to do anything with the DS0, DS1 solder points on the drive.
 
Now I need to flip one of my 5.25 and 3.25 drives so I have all combinations.
 

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