Tandon TM100-2 appears to be in mechanically working order, but never attempts to read disks.

[zanglucarson]

Hi all,
I've got a Tandon TM100-2 in my IBM XT, that works mechanically fine (spindle spins, head moves at startup, LED flashes, no 601 error), but it won't ever read any disks I attempt to insert. I've tried an official PC DOS 3.3 floppy (which works fine in my AT), as well as an unofficial DOS 6.22 disk, which also did not read.
I've cleaned the heads, but I'm not too sure what else to try.. I'm hoping it's not an alignment issue but I'm afraid I'm not totally sure what the symptoms of that would be.
I'm trying to boot using my XT-CF-Lite, using it and telling it to boot from the floppy simply produces a "2h error."
without it, the computer simply boots to BASIC.
I'm completely stumped! Any advice helps!

 

[hornbetw]

Can you format a disk in the drive and copy files to it and read them off? If you can do that, the drive works. Since the drive won't read disks written in another drive, it most likely needs to be aligned.

 

[zanglucarson]

Can you format a disk in the drive and copy files to it and read them off? If you can do that, the drive works.

I unfortunately don't have any blank 5.25 disks to attempt to write anything to. Even if I did, I have no readable OS on the computer. My known working XT-CF card hangs while attempting to boot into the FreeDOS CF I have written. But I'm fairly certain that's another issue.

Since the drive won't read disks written in another drive, it most likely needs to be aligned.

I was scared of that.. I guess I'll have to fix my oscilliscope first..

 

[SomeGuy]

If it isn't trying to boot the disk already, there is not a lot an XT-CF will do.

I'd first try swapping parts around. Do you have any other drives, controllers, or cables? Make sure the XT can actually boot from a floppy using some other drive. Perhaps try the floppy drive and even the controller on your AT. Try different cables and make sure you are using the proper twisted cables and that they are connected correctly. Perhaps try booting a 720k 3.5" disk on the XT using a 1.44mb floppy drive.

Once that is sanity checked, try booting from a hard drive or CF and try tools like DOS format and ImageDisk. Tools like Imagedisk bypass the BIOS can can sometimes tell you more about what is going on with the drive.

With a TM100-2, make sure to give the logic boards and connectors a good visual inspection. If this machine is new to you, a previous user may have borked it. Also, make sure the index sensor is clean and unobstructed.

 

[zanglucarson]

I'd first try swapping parts around. Do you have any other drives, controllers, or cables? Make sure the XT can actually boot from a floppy using some other drive. Perhaps try the floppy drive and even the controller on your AT. Try different cables and make sure you are using the proper twisted cables and that they are connected correctly. Perhaps try booting a 720k 3.5" disk on the XT using a 1.44mb floppy drive.

Hmm, I've got the two one slot drives, another controller, and some other cables (all known working) in my AT. I'll give them a try tomorrow and see how it goes.

Once that is sanity checked, try booting from a hard drive or CF and try tools like DOS format and ImageDisk. Tools like Imagedisk bypass the BIOS can can sometimes tell you more about what is going on with the drive.

Someone on Reddit suggested Imagedisk, I'll definitely give it a go if I manage to get the drive working with my known working parts.

With a TM100-2, make sure to give the logic boards and connectors a good visual inspection. If this machine is new to you, a previous user may have borked it.

I wouldn't be surprised if it were borked, the dips were all scrambled when I got it and one tantalum cap blew.

Also, make sure the index sensor is clean and unobstructed.

Index sensor? I'm unfamiliar
If you're referring to the sensors on the head, I've already tried that, went over them with isopropyl alcohol twice.

 

[modem7]

Assumption: Your IBM XT has the stock IBM floppy controller, the 'IBM 5.25" Diskette Drive Adapter', fitted. Pictured at [here].

I see a lot of focus on the floppy drive. Of course, the floppy controller has yet to be ruled out. Per [here], expected is that if a 1.44M drive is connected up to the controller, a 720K boot diskette (not a 1.44M one) can be booted from.

Connecting a 1.2M drive to the stock controller will not work, irrespective of whether the floppy is a 360K one or a 1.2M one.

 

[modem7]

My known working XT-CF card hangs while attempting to boot into the FreeDOS CF I have written.

Is that an {XT-CF + CF} combination that boots in other computers, but just not your IBM XT ?

 

[modem7]

Hmm, I've got the two one slot drives, another controller, and some other cables (all known working) in my AT. I'll give them a try tomorrow and see how it goes.

To note is that simply putting a standard high-density (HD) floppy controller and 1.2M drive into an IBM XT does not work.
See the {5.25" 1.2M drives} section of [here], which shows two examples of gaining 1.2M operation.

 

[zanglucarson]

Is that an {XT-CF + CF} combination that boots in other computers, but just not your IBM XT ?

I'm a bit confused by the question, it's a compact flash-card as well as an XT-CF-Lite card to be a bit more specific.
The only other computer I've tested it in is my IBM AT and it works completely fine.

 

[modem7]

Also, make sure the index sensor is clean and unobstructed.

Index sensor? I'm unfamiliar

See [here].

 

[modem7]

Assumption: The cause of the booting problem is the drive.

See also, the 'Deteriorated lubrication' section of [here].

 

[zanglucarson]

Assumption: Your IBM XT has the stock IBM floppy controller, the 'IBM 5.25" Diskette Drive Adapter', fitted. Pictured at [here].

Yep! that's the one.

I see a lot of focus on the floppy drive. Of course, the floppy controller has yet to be ruled out. Per [here], expected is that if a 1.44M drive is connected up to the controller, a 720K boot diskette (not a 1.44M one) can be booted from.

Connecting a 1.2M drive to the stock controller will not work, irrespective of whether the floppy is a 360K one or a 1.2M one.

I will certainly give it a try! I don't have any 1.44M drives handy at the moment, but I'll go out to my local e-waste place when I get the chance and do some scavenging!

To note is that simply putting a standard high-density (HD) floppy controller and 1.2M drive into an IBM XT does not work.
See the {5.25" 1.2M drives} section of [here], which shows two examples of gaining 1.2M operation.

I see. For clarification, would the standard stock floppy controller of an IBM 5170 be capable of using a 1.2M drive by default? I understand that the 5160's is uncapable of supporting 1.2M drives as they postdate the creation of the 5160.

make sure the index sensor is clean and unobstructed.

Just found it and wiped it off with isopropyl alcohol. No luck unfortunately.

Assumption: The cause of the booting problem is the drive.

See also, the 'Deteriorated lubrication' section of [here].

I relubricated the stepper motor earlier today, I did not however re-lube the rails. I'll do that right now.

 

[zanglucarson]

New development!!!
I inserted an IBM AT System Diagnostic disk just for funsies, and to my surprise, I got something new!
I got the message: "Bad or missing Command Interpreter"
It's not a great message but it's definitely trying to read the disk!

 

[zanglucarson]

I also just tried my IBM Exploring the PC AT disk which produced a "Disk Boot failure" error.

 

[modem7]

New development!!!
I inserted an IBM AT System Diagnostic disk just for funsies, and to my surprise, I got something new!
I got the message: "Bad or missing Command Interpreter"
It's not a great message but it's definitely trying to read the disk!

The boot sector was was successfully read into RAM then executed. The boot sector then got to the point of loading IBMBIO.COM (or IO.SYS if MS-DOS). Something went wrong when IBMBIO.COM went to load COMMAND.COM

I also just tried my IBM Exploring the PC AT disk which produced a "Disk Boot failure" error.

Per [here], that error is in the boot sector. The boot sector was successfully read into RAM, then something went wrong after that.

It sounds like a stepping problem. Did you get around to re-lubricating the drive's carriage rails?

You can get to Cassette BASIC, and so to gain some confidence (confidence only), you could try running the 'PROGRAM TO MOVE ...' program at [here], and see if you observe smooth and consistent stepping when you command various moves between tracks 0 and 39.

 

[modem7]

My known working XT-CF card hangs while attempting to boot into the FreeDOS CF I have written.

Is that an {XT-CF + CF} combination that boots in other computers, but just not your IBM XT ?

I'm a bit confused by the question, it's a compact flash-card as well as an XT-CF-Lite card to be a bit more specific.
The only other computer I've tested it in is my IBM AT and it works completely fine.

For me, the "I have written" needed clarification: "Is that superfluous, or is the OP informing us that the CF has only just been written to and is unproven?"

So you have a known-working XT-CF-Lite and CF combination, known working in an IBM AT. Sometimes it helps to know exactly which card it is. For example, the 'Lo-tech XT-CF-lite rev.2' default setting for the ROM's base (starting) address is C8000. Per [here], that would be a problem for IBM XT's that contain an MFM controller. Looking at the aforementioned web page, which XT-CF-Lite variant do you have?

And what are the exact symptoms? Getting as far as seeing the XUB's splash/banner screen? Getting as far as the XUB displaying the make-model of the CF card?

 

[zanglucarson]

For me, the "I have written" needed clarification: "Is that superfluous, or is the OP informing us that the CF has only just been written to and is unproven?"

I'm so sorry! major typo.

So you have a known-working XT-CF-Lite and CF combination, known working in an IBM AT.

Yes, I have a XT-CF as well as a 512 MB CF card with FreeDOS installed on it which are both known working in an IBM AT.

Sometimes it helps to know exactly which card it is

I've got Sergey's XT-CF-Lite V4.1 to be more specific.

And what are the exact symptoms? Getting as far as seeing the XUB's splash/banner screen? Getting as far as the XUB displaying the make-model of the CF card?

I get to the splash banner, where it detects the CF card and displays the make and model. From there it attempts to boot from the CF card saying "booting C>>C" at which point it hangs with a flashing cursor.
If it would be helpful I'd be more than happy to provide some proper photos of what I see as soon as I get home.

It sounds like a stepping problem. Did you get around to re-lubricating the drive's carriage rails?

I re-lubricated the rails as well as the stepper motor. It moves with a small amount of resistance (it doesn't move freely but will move if pushed with light force).

you could try running the 'PROGRAM TO MOVE ...'

I'll give that a try as soon as I can.

 

[modem7]

I've got Sergey's XT-CF-Lite V4.1 to be more specific.

I have the same card. As expected, it works in my IBM XT's.

I get to the splash banner, where it detects the CF card and displays the make and model. From there it attempts to boot from the CF card saying "booting C>>C" at which point it hangs with a flashing cursor.
If it would be helpful I'd be more than happy to provide some proper photos of what I see as soon as I get home.

Yes, a photo of the splash/banner/boot text may be helpful.

In the photo at [here], see how there is an "(XT)" appearing. It means that an XT version of the XUB is installed, something that will work on both an XT and AT. If your card shows "(AT") instead, then there is the problem.

When you get a DOS boot successfully happening, try the RAYXTIDE tool at [here]. It may detect a problem.

 

[modem7]

I have never used FreeDOS.
At [here] is "FreeDOS requires a PC/XT machine with at least 640 kB of memory."
Does your IBM XT have 640 KB fitted?

(Not being familiar with FreeDOS, I don't know what the symptom would be if less RAM was fitted.)

 

[modem7]

Something else.
If the two floppy-count switches on the motherboard are set for 3 or 4 floppy drives, that can cause a booting problem.

(One time, there was someone who thought they had the switches set to 1 floppy drive, but they actually had 4 drives selected, because they got on and off mixed up.)