OT: Trying to get a 3" FDD working.

[wyerd]

Yes, you did read it correctly, it's a Teac FD-30A 3" FDD. I recently acquired a Tatung Einstein TC01, so it's very, very slightly connected to the TI as it has the TMS9129.

 

The problem with the drive is that the read/write head doesn't move. The stepper motor tries to push the head, and then makes a buzzing noise after moving it about a millimetre or 2. I've tried to move it with my finger, but it feels jammed on something. I can't see anything causing the jam and it loads and ejects a Floppy disk ok.

 

Any ideas on what the problem is? Thanks.

[Stuart]

Can you push it easily that millimetre or two with your finger? Could be solidified grease/lubricant on the guide rail/rod that it moves on?

 

EDIT - there's a brochure that appears to show the drive - https://archive.org/stream/bitsavers_teacbrochueJan84_4393819/TEAC_FD-30A_Brochure_Jan84#page/n1/mode/1up. Looks like two screws securing the stepper motor in place. If you can get to those and remove them, then you should be able to check if the head is jammed on the guide rail, or the motor or lead screw is jammed.

Edited February 13, 2017 by Stuart

[wyerd]

Yes, I can easily push it the mm or 2, then I can feel the jam. The rail looks clean.

Edited February 13, 2017 by wyerd

[wyerd]

Looks like two screws securing the stepper motor in place. If you can get to those and remove them, then you should be able to check if the head is jammed on the guide rail, or the motor or lead screw is jammed.

Does one of the screws have a spring on it?

[Stuart]

Looking at the photo at the bottom of page 2 of the brochure linked to in post #2. At the extreme right of the photo are two screws, screwed in from the right to the left, one near the top of the photo and one near the bottom (the heads of the screws have been partially cropped from the photo). They appear to the holding a plate that secures the stepper motor to the chassis. If I'm right, and if you can get to them and remove them, then you can probably slide the stepper motor and head assembly to the right a bit, which gives you a bit more room to carefully wiggle bits and see where the obstruction is. I may be wrong about what those screws are holding though - difficult to tell from the photo at that angle.

 

Have you tried rotating the lead screw from the stepper motor to the head by hand? Assuming it isn't seized (which may be what the problem is), it's probably possible to turn it and it will feel probably feel 'notchy'. (Don't turn it too far though in case the head is tight up against a limit switch)

[wyerd]

Looking at the photo at the bottom of page 2 of the brochure linked to in post #2. At the extreme right of the photo are two screws, screwed in from the right to the left, one near the top of the photo and one near the bottom (the heads of the screws have been partially cropped from the photo). They appear to the holding a plate that secures the stepper motor to the chassis. If I'm right, and if you can get to them and remove them, then you can probably slide the stepper motor and head assembly to the right a bit, which gives you a bit more room to carefully wiggle bits and see where the obstruction is. I may be wrong about what those screws are holding though - difficult to tell from the photo at that angle.

 

Have you tried rotating the lead screw from the stepper motor to the head by hand? Assuming it isn't seized (which may be what the problem is), it's probably possible to turn it and it will feel probably feel 'notchy'. (Don't turn it too far though in case the head is tight up against a limit switch)

 

I've linked a video and some photos I look the last time I took it apart. You can see the spring on the screw - is there a special purpose for it? I don't want to take it apart without knowing why it's there!

 

http://kimberlinwyer.com/tatung/IMG_0158.mov

 

 

 

[+Schmitzi]

Sounds like a tattoo machine

 

is this 3" drive for Compact Floppy Disks like "CF2" used by Amstrad machines ?

[Stuart]

The spring allows that side of the motor mounting to move a bit - it is held to the chassis under spring pressure rather than being firmly screwed to it.

 

Looking at the video - before taking the motor off, look at the bit that rotates a little in the video. With power off, can you rotate that by hand in the opposite direction to move the head towards the disk centre? If yes, repeat your test and the head moves back towards the stepper motor and starts buzzing? The head mechanism should actuate a switch when it gets to the outermost disk track - track 0 - then stop. If that switch (or the associated electronics) has failed then the motor will just keep on trying to move the head and make that buzzing noise. The bit of board with the three wires going to it - has that got an optical switch like this http://cpc.farnell.com/productimages/standard/en_GB/491342-40.jpg on it, and there's a bit of plastic on the head assembly that breaks the beam between the two halves?

[wyerd]

is this 3" drive for Compact Floppy Disks like "CF2" used by Amstrad machines ?

Similar. The Amstrad uses a belt driven drive and my Einstein uses a vastly superior direct drive, which is better as there isn't a belt that can wear and need replacing In fact, the previous owner thought it was the belt that had broken causing the buzzing noise and had included a spare one with the purchase!

Edited February 16, 2017 by wyerd

[wyerd]

The bit of board with the three wires going to it - has that got an optical switch like this http://cpc.farnell.com/productimages/standard/en_GB/491342-40.jpg on it, and there's a bit of plastic on the head assembly that breaks the beam between the two halves?

Which 3 wires are you referring to Stuart?

[Stuart]

wyerd, on 16 Feb 2017 - 7:08 PM, said:

Which 3 wires are you referring to Stuart?

 

In the last of your pictures above, there are three wires (white/blue/red) going from the green PCB to a small board next to the black plastic bit. Is there an optical sensor on that small board?

[wyerd]

 

In the last of your pictures above, there are three wires (white/blue/red) going from the green PCB to a small board next to the black plastic bit. Is there an optical sensor on that small board?

 

No, no sensor.

 

I removed the stepping motor and was then able to rotate the rod in the middle of the motor freely.

 

 

I was also able to move the read/write carriage freely along the rail too.

 

 

So it looks like an issue with the stepper motor somehow. I need someway of testing it while it's removed from the FDD unit. Any ideas?

 

Thanks for your help so far Stuart.

[Stuart]

Can you do a couple of close-up pics of that small board from various angles? What's on it?

 

Do you have a multimeter available?

Edited February 18, 2017 by Stuart

[wyerd]

Can you do a couple of close-up pics of that small board from various angles? What's on it?

 

Do you have a multimeter available?

 

 

 

 

The small board just has wires going to the read/write carriage. Can't see anything else of interest. I do have a multimeter

[Stuart]

Hmm. I reckon there's got to be a switch or sensor associated with that small board. In the first two photos above there are some silver pins coming out the opposite side to where the wires come in - can you see where they go to?

 

With the photo of the removed motor, there are two bits of black plastic on the motor shaft. Are they both free to rotate on the shaft, or locked to the shaft? The piece nearest to the motor - is that completely round or does it have anything projecting from it? Is there anything set into the plastic, like a small magnet?

[wyerd]

Hmm. I reckon there's got to be a switch or sensor associated with that small board. In the first two photos above there are some silver pins coming out the opposite side to where the wires come in - can you see where they go to?

The pins go into the side of the carriage. Can't see much else.

With the photo of the removed motor, there are two bits of black plastic on the motor shaft. Are they both free to rotate on the shaft, or locked to the shaft? The piece nearest to the motor - is that completely round or does it have anything projecting from it? Is there anything set into the plastic, like a small magnet?

The piece on the end of the shaft has a tongue that sits in the carriage which then moves it during operation. The movement I detected earlier was the play between them. The other piece is round and is free to spin. A small section has some metal on it.