Floppy A is found but won't read disk.

I have an old 486 pc.

I recently took it apart to clean it but when I put it back together the floppy drives are not working.

I have two drives, one 3.5 and one 5.25 both are confirmed working as they were tested on another machine.
The 3.5 one shows up in bios but won't read a known working disk. The 5.25 won't show up at all.

When I have both plugged it the drive usage light stays on.

Welcome to the forum @Jentralith .

Check to make sure that your floppy cable is in good condition. Remember to have the A drive on the last connector, after the twist, like what is shown here:

Also you can check the jumper settings on your drive. For use on a PC, both drives should be set for DS1. Again, the link above can help.

- Alex

Jentralith said:

drive usage light stays on

Click to expand...

I think i've seen that behavior (drive light steady on) when the 34 pin connector to the 3.5 drive has been plugged in upside down?

I check

ajacocks said:

Check to make sure that your floppy cable is in good condition. Remember to have the A drive on the last connector, after the twist, like what is shown here:

Also you can check the jumper settings on your drive. For use on a PC, both drives should be set for DS1. Again, the link above can help.

Click to expand...

I checked that the cable worked on another pc. I tried a different cable that also works with only one connector on it plugged into the 3.5 drive, with no success.

The 3.5 has no jumpers, the 5.25 was set to ds1. I tried setting it to ds0 and only connecting that one, same issue. Drive is found but won't read.

So I know both drives work having just tested them on a separate computer. I know the disks work because they were also tested.
The cable I'm using works as it's been tested.

Separately I can make either drive appear as A: but together I only get A: no B:
And no matter the configuration the A: is found but will not read the disk.
Listening to the 3.5 drive and visually looking at the 5.25 because it's open, there is no spinning occurring at all.

Lastly I decided to check the voltages on the power cable and got a 12v and 5v

Motherboard is an Intel Advanced/ZP (Zappa)

Floppy drives weren't generally weren't detected by the bios in the 486 era, they were set in the bios.

The light staying on for the 3.5 drive is definitely the ribbon cable installed backwards.

The 5.25 drive should be set to DS1, all floppies in an IBM PC compatible are set to DS1. the determination of A is after or before the twist in the cable.

Jove said:

The light staying on for the 3.5 drive is definitely the ribbon cable installed backwards.

Click to expand...

Yes, most likely. Every time that I have done work on a computer, then at power-on time, seen the floppy/diskette drive's LED on solid, I have said to myself, "I must have fitted the cable's connector to the drive on upside down", and sure enough, it turns out that is what I did.

ajacocks said:

For use on a PC, both drives should be set for DS1.

Click to expand...

Jove said:

... all floppies in an IBM PC compatible are set to DS1.

Click to expand...

That is not always correct:

1. There are some IBM PC compatibles (such as the Amstrad PC1640) that do not use the twisted cable that the IBM PC family use; they use a 'flat' cable.

2. For IBM PC compatibles that use the twisted cable, it is the second drive-select position that is used. For drives (such as the Panasonic JU-475-2) that have DS1-DS2-DS3-DS4 jumpers, DS2 is selected. For drives (such as the Toshiba ND-0801) that have DS0-DS1-DS2-DS3 jumpers, DS1 is selected.

Both cables I've tested with have the twist in the wire.

First one is is a single connected. Plugged into a 3.5 drive. POST shows Floppy A Installed. I put in a know working disk select A drive and get the Failure Reading Drive A message.

Second Cable has two connectors the middle one is the 5.25 connector type and the end one is the 3.5 connector type. Set the 5.25 to ds1 and connecting both drives.
POST says Floppy A Installed. Try known working disks in both drives. Failure Reading Drive A or B deppending on which one I try.

@Jentralith can you post pictures of the various setups you've tried.

Jentralith said:

POST shows Floppy A Installed.

Click to expand...

On some computers, the POST (power-on self test) could display that ONLY because the user informed the POST, via CMOS SETUP, that an A: drive is installed.
Personally, if I was the author of the POST, and wanted to indicate to the user that I found drive A:, I would display "Drive A: found".
If the POST did indeed find the drive, we expect that you saw the drive's LED flash on for a short while during the POST.

Note too that the POST of some motherboard BIOS may attempt to see if A: is present, but make no attempt to see if B: is present.

Jentralith said:

I recently took it apart to clean it but when I put it back together the floppy drives are not working.

Click to expand...

And from that, we know that your motherboard/BIOS is not the type that only supports one floppy/diskette drive.

(I.e. You didn't write something like, ".. and I decided to add a second floppy drive whilst I had the computer open.")

Refer to the diagram at [here].
In my opinion, there is no point in trying configuration #3 if configurations #1 and #2 do not work ('work' = I can read a floppy/diskette put into the drive).

Am I understanding right that both the drives and the cables have been tested and work fully on another computer?

That does not really leave a lot left to test. Check the header on the motherboard and see if any pins are bent or broken.

If it were me, I'd try testing with ImageDisk, as that bypasses any DOS or BIOS issues. Although, do make sure the right drive types are set in the BIOS setup.

First make sure the drive lights come on when the drive is accessed, and that the drive spins when accessed with a disk in the drive.

With Imagedisk, you can use an "alignment" test to manually step the head. Verify that the heads move and seek back to track zero. (Note that alignment is not the issue here)

The alignment test also will try to read the tracks, and display information about any sectors it can find under the head - even if the head is over the wrong track. That will let you know if it is reading or not.

Imagedisk can also test formatting and writing sectors, but clearly the machine is not getting far enough for those to matter at the moment.

VeryVon said:

@Jentralith can you post pictures of the various setups you've tried.

Click to expand...

I can try taking pictures if you want, however it's currently in a case and it's not easy to see the cables and such in terms of what connects where.

Basically the tests look something like this (= is twist)

MB------EMPTY---=--3.5
MB-----=---3.5
MB------5.25(Set to ds1)----=----3.5
MB-----5.25(Set to ds0)-----=-----EMPTY

modem7 said:

If the POST did indeed find the drive, we expect that you saw the drive's LED flash on for a short while during the POST.

Click to expand...

Any of the drives I had plugged in would have the led flash briefly.

modem7 said:

And from that, we know that your motherboard/BIOS is not the type that only supports one floppy/diskette drive.

(I.e. You didn't write something like, ".. and I decided to add a second floppy drive whilst I had the computer open.")

Click to expand...

In the BIOS there are settings for Drive A and B and they list all the usually floppy types.

SomeGuy said:

Am I understanding right that both the drives and the cables have been tested and work fully on another computer?

That does not really leave a lot left to test. Check the header on the motherboard and see if any pins are bent or broken.

Click to expand...

Yes they have all be tested on another computer a few days ago when this issue first started.

There are no bent or missing pins(other then the usual missing pin in the floppy connector)

SomeGuy said:

If it were me, I'd try testing with ImageDisk, as that bypasses any DOS or BIOS issues. Although, do make sure the right drive types are set in the BIOS setup.

First make sure the drive lights come on when the drive is accessed, and that the drive spins when accessed with a disk in the drive.

Click to expand...

I've not yet tried the mention ImageDisk but I do know that the drives are NOT spinning at all.

With the 3.5 I can usually here the spinnig sound but not in this case. As for the 5.25 I've had the drive connected but sitting out of the case.
The disk did not spin and the head did not move.

If you were as diligent in cleaning as I suspect, removing the CMOS battery to get the gunk out from under it forced you to "load defaults" the first time you booted it. There's a really good chance that the defaults aren't necessarily what the drive's capabilities are. I have a MB that defaults to low density settings that will result in a seek at boot but no disk read.

Go into setup, make sure both floppies are set correctly in size and capacity, and let us know.

I managed to get the 3.5 drive working correctly by setting it correctly in setup. It was initially set as 360k 5.25

I still can't get the 5.25 to do anything. The light comes on when the computer first boots and it comes on when trying to access the drive.
The drive however does not spin or move the head. The drive is a 360k one and has been set to that in setup.

What happens if you place the 5.25" drive at the end of the cable instead of the 3.5"? Does it then spin?