25
Mar
14

Fixing a NEC FD1157C floppy drive

NEC FD1157C

NEC FD1157C

Last time I went to see my family out in the bush I had a look at some of the hardware I had in storage there. I found I had a NEC FD1157C 5.25″ floppy disk drive made in 1989 that had come from an Epson machine one of my uncles had given my father. The drive, whilst badly yellowed looked like it was in good shape mechanically, but upon testing with hardware I had on hand at my parents place it didn’t work. It didn’t even seem to seek properly.

This drive has a number of jumpers on the main circuit board, so I checked online to find out the settings. After trying for a while I still couldn’t get it to work. I decided I’d bring it back with me to try to work out what was wrong. I have better diagnostic equipment here.

The head rails

The head rails

Having been doing other things I hadn’t had a chance to look at it until just this weekend gone. I rechecked the mechanism to see that it moved freely. This type of head travel mechanism is nice in the sense that it doesn’t have a screw to lubricate, so it’s a bit cleaner, easier to adjust, and reliable.  Fortunately it didn’t require service as the heads moved backwards and forwards freely. The spindle motor similarly was in good condition.

It seemed likely a problem on the circuit board, perhaps a bad jumper setting. So I rigged the drive up in my MS-DOS machine and in the process of setting up the BIOS for testing the drive it performed the drive seek test and seemed to work. I was quite surprised by this as I couldn’t get it to do that at all at my folks place. I found the website with jumper settings for some NEC drives.

Circuit board

Circuit board

After setting the jumpers the drive appeared to work but the drive light didn’t ignite when the drive was in use. I tried a few things and found that the LM1 setting on the drive needs to be 1 rather than 0 for the light to work. I was a little disappointed to not get to use my oscilloscope to check the test points.

I’ve done some minimal testing and everything appears fine, but I will test it against my reference working drive to make sure the alignment is right. I want to make sure it reads and writes to disks reliably without damaging them. I might even probe some of the test points just for fun! This drive is a good one to have as it appears more serviceable than others I have. Although I have to wonder why it didn’t work when I tested it at my folks place. Perhaps a bad cable?

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2 Responses to “Fixing a NEC FD1157C floppy drive”


  1. 1 goughlui
    March 25, 2014 at 8:48 am

    Every 5.25″ drive is worth saving nowadays – they’re getting harder to find, they’re also getting harder to keep running sometimes. Glad to see the effort being put in.

    The Panasonic OEM drive for HP that I have only lost its lubrication on its stepper screw, so that was no problem to “fix”. It also needed a clean, which was also relatively painless.

    I’m not as much of a stepper-and-metal-band type system that the Teacs seem to use – they seem a little more mechanically fragile to me, but you’re right – less grease all over the place!

    Getting the jumper settings right can be cryptic. Sometimes you don’t get it working/lighting up because of the Drive Select 0 / 1 difference between IBM and “other” machines. Other times (even just recently), unseating and re-seating the edge connector cleaned off enough “dust” that it made a good contact the second time (it failed calibrating the first time, and worked the second time).

    Glad to hear it sounds good though! It’s definitely a priceless asset when it comes to salvaging those last few 5.25″s that might come your way :).

    • March 25, 2014 at 9:56 am

      I got lucky to be given this particular one, I only had two other drives of this size. They are often quite expensive if you try to buy one, that’s if you can find one!

      I think the stepper screw is a newer type of mechanism, I’ve only seen it in a few 5.25″ drives and only newer ones at that. I agree that this arrangement looks more fragile, but I’ve never seen or heard of them failing. The much older Tandon drives from the first IBM PC and other machines used this arrangement. Maybe I’ve just been lucky.

      At least this particular drive doesn’t require a belt like other older ones. The belts frequently wear out, can melt, and even expire when not used at all.

      One of the best features of this are the numerous test points on the board. I’d actually be able to properly service and align it if I ever need to. My other drives don’t have any labeled test points so I’d have less chance of finding any real issues.

      A factor I didn’t mention for setting the jumpers for the PC is the cabling and whether there is a twist in your cable. If there is a twist, drives should all be configured as the first on the cable, but cables without the twist require the drives be set to the number you wish them to use. 3.5″ and later 5.25″ drives often don’t have the jumper to select which drive, as they are designed for cables with a twist or only one drive. Sometimes they have the pads and a solid link wire you can move if you’re handy with a soldering iron.

      Cheers
      Spacie


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