TI 99/4A Disk Drive Not Initializing Disks

[System Engineer]

Hello Everyone,

 

I just got a PEB and was also able to find a box of SS/SD Floppy disks.

I'm using Disk Manager 2.

When I try to initialize a disk, it finds the disk and says that it is not initialized.

I then start the initialization process:

SS: Yes

SD: Yes

40 Tracks

It runs for about ten minutes and and gets up to around 340 and then fails with a "Disk Error 41".

While it's running, it seems to be doing the correct process based on the LED activity between the flex cable interface and disk controller and the red drive light.

Any help would be greatly appreciated.

 

Thanks,

Scott

 

[HOME AUTOMATION]

Hi Scott,

Welcome to the Forum!

 

Have you checked this?

 

    -Alex

[System Engineer]

Hi Alex,

Thanks but that thread became a non-issue/self fix pretty quickly.

Seems like my problem is different...I took everything apart and all looks fine mechanically.

I don't understand why it would go up to 340 and fail and also take so long to fail.

I'm hoping someone has seen this very high count and long wait issue before.

[HOME AUTOMATION]

3 hours ago, System Engineer said:

I don't understand why it would go up to 340 and fail and also take so long to fail.

That CAN happen!

 

Here's another...

 

[System Engineer]

Got it...I'm going to try using a 5.25" half height drive I have and see if that works.

It will at least tell me if I have a drive issue or a drive controller issue.

Thanks

[System Engineer]

OK...I was able to use another half height 5.25" floppy and everything works great.

So, that means my original full height TI drive has a problem.

It's a Model PHP-1250

I examined the drive mechanics while trying to initialize it and notice that the stepper motor never moves the heads on the carriage.

I can move it manually and it is very clean and moves easily so I don't think it's a lubrication or cleaning issue.

Any suggestions or ideas?

Does anyone repair floppy drives?

Thanks

[+Ksarul]

Is your drive the Shugart or the MPI drive? The MPI drive has a whole door that slides open and the drive flings the disk partway out, whereas the Shugart drive just has a (somewhat) wide latch that you open and close to insert/lock down the disk. Note that the MPI drive is belt driven, and those belts get old and loose. . .

[System Engineer]

Hello Ksarul,

It's a Shugart Associates Model No. - 400L R, Serial No. - MT5616.

The belt is in perfect condition and the drive spins properly.

It just seems like the stepper motor isn't moving the read head back and forth.

I'm not able to see the disk that the stepper motor turns to see if it's moving.

I can only see that the head doesn't move back and forth on the rails.

Any help/direction would be appreciated.

Thanks,

Scott

[Stuart]

Not sure that the head should move easily as doesn't that model have a pin on the head mechanism that engages in a spiral plate that is rotated by the stepper motor to move the head? Can you rig it up so you can see the plate to see if it rotates, and the head mechanism has somehow become disengaged?

[RXB]

12 hours ago, System Engineer said:

Hello Ksarul,

It's a Shugart Associates Model No. - 400L R, Serial No. - MT5616.

The belt is in perfect condition and the drive spins properly.

It just seems like the stepper motor isn't moving the read head back and forth.

I'm not able to see the disk that the stepper motor turns to see if it's moving.

I can only see that the head doesn't move back and forth on the rails.

Any help/direction would be appreciated.

Thanks,

Scott

Personally I use 3.5 Drives as they are faster to carry / store and are more protected from dust and the elements.

Secondly the sheer number of 3.5 drives around is pretty insanely easy to get.

I use Panasonic 3.5 drives or there are many other makes to choose from.

 

After you get the 3.5 drives working you can go back to 5.25 and see it you can fix them.

[System Engineer]

Thanks guys,

 

Stuart: You are correct...It's actually a tiny spring loaded ball bearing that rides inside a channel on a disk that the stepper motor turns.  It is about impossible to see that darn disk but I may be able to tape a small mirror in a strategic location to view it.

 

RXB: Interesting with the 3.5" drives...Are they 720K or 1.44M...Also, do you just use a normal ribbon cable like a windows 98 or XP computer would use with a 3.5" drive?  Will the normal disk manager initialize/format the disks OK and how much space do you get?

 

 

[+Ksarul]

12 hours ago, System Engineer said:

Thanks guys,

 

Stuart: You are correct...It's actually a tiny spring loaded ball bearing that rides inside a channel on a disk that the stepper motor turns.  It is about impossible to see that darn disk but I may be able to tape a small mirror in a strategic location to view it.

 

RXB: Interesting with the 3.5" drives...Are they 720K or 1.44M...Also, do you just use a normal ribbon cable like a windows 98 or XP computer would use with a 3.5" drive?  Will the normal disk manager initialize/format the disks OK and how much space do you get?

 

 

A couple of important things to note on 3.5 drives. Using them with a standard TI controller and the original DSR chips, you get data on the first 40 tracks of each side in single density, format (90K per side, 180K per disk). Note that the last 40 tracks of each side of the disk will be completely unused, and this format will not be easily read by other TI equipment. This is caused by the fact that the TI does not know to double-step when formatting a 3.5 disk in 40-track mode, so it single-steps and makes really strange disk geometries.

 

There is a bit of a solution here, in that you can modify the DSR so that it formats 80 tracks per side (modified DSR chips are available from @atrax27407 for a reasonable fee). These disks would now be 180K per side--360K per disk. It is generally better to use 720K drives here, but the 1440K drives will downshift to 720K mode when used with 720K floppies. Note you can't get double-density from a TI controller, but this method of adapting it to use as much of the 720K disk as it can is pretty much compatible with any TI modified to read/write in 80-track mode.

 

Ribbon cables are a bit different. TI controllers don't expect the twist in the cable that is normal for PCs--the TI wants the cable to be straight through. This is yet another reason to use a 720K drive, as most of those actually have drive select jumpers for up to four different drives on a cable (some use 0-3 as the ID on the mask, others use 1-4, but all distill down to the same four electrically identical addresses as far as the computer is concerned), so no modifications to the cable are required.

 

With 1.44M drives, most of them are hardwired to be drive "B" (disk 2), and don't have options to set the drive selection differently. You can build a cable that moves the desired drive select wire in the cable to the disk 2 select position on the drive to get it to respond as a different drive (that's what the twist does for the PC, but it also switches other wires that mess up the TI controller, which is why you need a "mostly" straight through cable at all times).

[System Engineer]

Ksarul: Thank you for the clear and thorough explanation...I have a couple 1.44MB drives I can experiment with.  I'll use the non-twisted connection on a multi-drive ribbon cable I have.  I will tape over the hole on a 1.44MB floppy to fool the drive into thinking it's a 720K.  I'll just stick with the 40 tracks for now and maybe play around with the 80 track modification later.  Have a nice weekend, Scott

[mvancopp]

On 12/11/2023 at 11:55 PM, System Engineer said:

Hello Everyone,

 

I just got a PEB and was also able to find a box of SS/SD Floppy disks.

I'm using Disk Manager 2.

When I try to initialize a disk, it finds the disk and says that it is not initialized.

I then start the initialization process:

SS: Yes

SD: Yes

40 Tracks

It runs for about ten minutes and and gets up to around 340 and then fails with a "Disk Error 41".

While it's running, it seems to be doing the correct process based on the LED activity between the flex cable interface and disk controller and the red drive light.

Any help would be greatly appreciated.

 

Thanks,

Scott

 

The TI formats from the outside of the disk and marches inwards towards the middle for the higher track numbers. If the lower tracks (outer tracks) are working but the higher tracks (inner tracks) fail, then this is likely a speed issue. The outer tracks have more surface area to store the flux changes (your data and the overhead data). As the head moves inward that surface area decreases but you're trying to store the same amount of data. Some systems use a variable number of sectors per track to adjust for this. Commodore does that I believe. 

My suggestion is to adjust the speed of the drive rotation and see if you can make it work. A lot of drives have a sticker on the spindle to set the speed visually. The sticker usually has 50hz and 60hz lines, use the 60hz for the USA. On the back of the Tandon drives is a PC Board with and adjustable resistor, a potentiometer (a POT). Before changes its position, you should note its starting point. When the drive is spinning, like in formatting, watch the lines on the sticker and adjust the POT to change the speed. The goal is to make the lines look like they are standing still, not moving left or right. This is best done under an artificial light source; an incandescent bulb should do.

No guarantee it's the issue but it should be fairly easy to test and adjust if needed.

 

Fingers crossed and good luck!

[RickyDean]

 

11 minutes ago, mvancopp said:

 

My suggestion is to adjust the speed of the drive rotation and see if you can make it work. A lot of drives have a sticker on the spindle to set the speed visually. The sticker usually has 50hz and 60hz lines, use the 60hz for the USA. On the back of the Tandon drives is a PC Board with and adjustable resistor, a potentiometer (a POT). Before changes its position, you should note its starting point. When the drive is spinning, like in formatting, watch the lines on the sticker and adjust the POT to change the speed. The goal is to make the lines look like they are standing still, not moving left or right. This is best done under an artificial light source; an incandescent bulb should do.

 

 

Back in the 90's when I bought out the stock of DWright Stuff, Delbert Wright taught me that under a florescent light was the best way to adjust the spin as it cycled at the 60hz require and was much easier to see the lines stand still.

[System Engineer]

mvancopp & RickyDean:  Thanks guys...This is good information...I will clean my eyeglasses and give this a shot.

[mvancopp]

On 12/17/2023 at 1:36 PM, System Engineer said:

mvancopp & RickyDean:  Thanks guys...This is good information...I will clean my eyeglasses and give this a shot.

If the speed does not work, there is one other thing I can think. Once, just once, (sorry couldn't resist the "Johnny Dangerously" quote) I ran into a Tandon drive that the alignment was so for off it went beyond the area the magnetic material on the inner tracks. This was on an Atari 810. The Tandon drives have what I consider a painful alignment mechanism. So, to prove if it an alignment is an issue. Format a disk in the HH drive you have and then try and read it with the Tandon. If it works, then it is not likely a far-off alignment. If it doesn't work, you can try and align the Tandon using the HH formatted disk.

For the Tandon, the entire head mounting mechanics are moved during the alignment. You must loosen two screws underneath and one on top. You then use the screw to the left of the mechanism set screw (looking from the front). On the drive I mentioned above I had to remove the "alignment" screw, there wasn't enough adjusment range when it was in place. Once removed and with and lot of delicate manual movement of the head mechanics, the drive was able to read other drive formatted disks, was able to successfully format a disk, and it's formatted disk was successfully read by other drives. I do not know why the alignment was so far off. Nothing looked very worn.

Just FYI in case the speed suggestion doesn't pan out.

 

[System Engineer]

Thanks mvancopp...The more ammunition in the arsenal, the better!

[+OLD CS1]

3 hours ago, mvancopp said:

(sorry couldn't resist the "Johnny Dangerously" quote)

You fargin bastige!