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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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24th May 2021, 4:09 pm | #1 |
Hexode
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
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TEC FB-504 5.25” FDD, Disc centralising
Hi All,
I have just repaired two of these drives out of a Cumana dual unit for the BBC computer. The problem was leaking capacitors on the main board that had corroded the tracks, one drive would read and the other would not read or write. I have replaced the capacitors and cleaned the board, several links had to put on the boards to fix open circuit tracks, a lot of the tracks are only 0.010” wide. Both drives read and write now but I have noticed with both drives that when you insert a disc the spindle motor does not run to centralise the disc. These drives have a lever you turn down through 90 degrees to clamp the disc in place. See picture. Can anybody tell me if this is normal for this type of drive? Regards,
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Andrew Illegitimi non carborundum |
24th May 2021, 4:46 pm | #2 |
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Re: TEC FB-504 5.25” FDD, Disc centralising
Normal, the disk is cantered by its hole, no amount of spinning will make it any better. The head positioning is open loop.
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24th May 2021, 4:56 pm | #3 |
Hexode
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
Thanks Merlin, I could have sworn it span but I must be thinking of other drives. That will save me trying to find a non-existent fault!
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Andrew Illegitimi non carborundum |
24th May 2021, 5:30 pm | #4 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
That’s a brand I’ve not seen for a long time, takes me back to school days.
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24th May 2021, 8:14 pm | #5 |
Hexode
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 298
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Re: TEC FB-504 5.25” FDD, Disc centralising
They were used in TRS-80 computers as well.
They look well made, die-cast alloy chassis, Elna caps on the motor board, pity about those on the main board, 2 of the 4 in each drive had leaked, different ones fortunately so it was easier to trace out the open circuit tracks on these double sided boards. Some of the components are tiny so the next step would be surface mount. I’m glad to have saved them. One of the failed caps attached. Regards,
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Andrew Illegitimi non carborundum Last edited by MeerKat; 24th May 2021 at 8:21 pm. |
24th May 2021, 9:29 pm | #6 |
Dekatron
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Location: West Cumbria (CA13), UK
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Re: TEC FB-504 5.25” FDD, Disc centralising
As far as I recall, this lever is common to most (if not all) 5¼" drives that I've used.
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25th May 2021, 12:24 am | #7 | |
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Re: TEC FB-504 5.25” FDD, Disc centralising
Quote:
The Teac FD-50 had a clamp arrangement. Apple Disk IIs had a flap-type thing. Apple UniDisk and DuoDisk units had a similar clamp to the old Teacs. |
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25th May 2021, 12:30 am | #8 |
Hexode
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 298
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Re: TEC FB-504 5.25” FDD, Disc centralising
These mid 80s Mitsubishi 5.25” drives, the black ones at the bottom, are a different arrangement to the TEC turn lever drives.
LOADING. You insert the floppy, the last inch is against light spring pressure, the floppy clicks lightly as it bottoms in the slot and you can hear the spindle motor start, then push the top lever down, this clamps the disc, locks the floppy in and the motor stops. You are ready to go. I have always presumed, perhaps wrongly, the motor running during the clamping phase helps with alignment of the disc hole. UNLOADING. Push in the lever below the floppy slot, the top lever jumps back up and the floppy emerges about an inch ready for you to slide it out. This is where my thoughts of the spindle motor starting when you insert a disc came from. You can see in the picture the top drive is empty and you can just see a floppy in the lower one. Regards,
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Andrew Illegitimi non carborundum Last edited by MeerKat; 25th May 2021 at 12:35 am. Reason: Post has crossed with arjoll's |
25th May 2021, 9:40 am | #9 |
Dekatron
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Location: West Cumbria (CA13), UK
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Re: TEC FB-504 5.25” FDD, Disc centralising
Now that Arjoll has drawn my attention to Apple using a flap rather than a lever, I can confirm that the drives on my Apple ][ are an exception, whereas most of my 5¼" drives use a lever.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
25th May 2021, 9:50 am | #10 |
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
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Re: TEC FB-504 5.25” FDD, Disc centralising
I've got various BBC Micro floppy drives here. Some of them run the motor when the disc is inserted, some don't. My original Shugart SA-455 drives do run the motor for a moment when the disc is put in, long enough to centre it when you turn the lock lever. Other, more recent, drives (can't remember the manufacturer) don't do it.
Chris
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25th May 2021, 10:12 am | #11 |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
I seem to remember with the flap-type, which originated on full-height drives, that if the disk wasn't fully pressed in then you could end-up bringing the clamp down quite a bit off-centre and so crushing the disk.
Some of these also had an extra slide-lock button I did rather prefer the lever-type, used by Teac etc. on most half-height drives, especially over the less-common smaller-flap ones. And I recall that some lever-types would eject the disk a bit when lever was released, so had to be be a bit careful to push it back in fully, if turning the lever again. I seem to recall a 4th type, with a button that you pressed to lower the clamp, and pressed again to release it and eject the disk a bit. |
25th May 2021, 4:11 pm | #12 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
One of the common makes of push-button lock/eject drives was Epson. You put the disk in and pressed the button to lower the hub cone and lock it in. The press the button again to release it and the disk would then be ejected by a spring thingy so you could grab it.
The half-height one was as far as I know conventional inside. But there was also a 1/3d height one, turns up in the QX10 and the TF20 disk unit for the laptops, that had a voice coil head positioner. It was almost like a miniature RK05 head mechanism for those who remember that far back. Very odd... There was also a drive, I think BASF, where the entire front panel was a door with a press to lock, press to release catch. You opened the door, slid the disk in, then closed it and it latched, lowering the hub cone. Something tells me the drive was an odd overall size, perhaps 2/3rds height. I've come across them in the RML 380Z. My experience is that the very early drives didn't spin the motor when you inserted a disk, later ones often did. It was claimed to help to centre the disk, I have no idea if it actually did. |
25th May 2021, 10:48 pm | #13 |
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Re: TEC FB-504 5.25” FDD, Disc centralising
The disc drive I used with my Beeb was a 40 track, single sided unit. Half height, with a clamp that had to be pulled down to lock the disc in, and pulled down again to release the disc and flick it out enough to grab hold of. It might well have been an earlier version of the Epson mechanism Tony described, just with the clamp actuated directly as opposed to via a plunger and bell-crank arrangement.
I can't remember for sure if or not it did a brief self-centring spin when closed. It might have, but it's just as likely I am remembering a 5.25 drive from one of many other systems I have used since. They definitely did not all do it.
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26th May 2021, 1:09 pm | #14 | |
Octode
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Location: Northampton, Northamptonshire, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
Quote:
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26th May 2021, 5:10 pm | #15 |
Octode
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
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Re: TEC FB-504 5.25” FDD, Disc centralising
The H17 drive cabinet for the H8 has a drive with a full front panel that drops the cone when you close the cover. I think mine is the early WANGCO model 82 that became the Siemens FDD100-5.
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