Nprod wrote:Anybody know a guide for doing head alignment on 5.25'' drives? I have a J.P.N. Corp. DS-53A drive that doesn't want to read or format any disk. I know at least some of the disks are good because they format and read on another drive (a Chinon one) and after having lubricated the rails, cleaned the heads and the index sensor i can't think of any other options.
Read it all before adjustment.
1. You got to have 2 things: DOS and IMDisk from here http://www.classiccmp.org/dunfield/img/index.htm
If you don't have pure DOS, get FreeDOS. Make a bootable USB pendrive and download SystemRescueCD (it has some console text tools like memtest, mhdd, freedos) and put also unpacked IMD118 files in there. When starting FreeDOS from thumb drive, make sure you pick '0' (zero) to disable all memory managers or it will crash.
2. Make sure that your MB supports 1.2MB 5,25" drives. I tested mine on asus P5W on a quad core cpu - worked fine
3. Unscrew upper shield covering the heads module. Loosen the two big screws that hold step motor in place. You will be moving it back& forth to get a reading. Sometimes, the screws are on the bottom, eg. in NEC drivers. Check with your drive and user manual.
4. Insert a disk and start imd118. Select alignment test. What should interest you are the last two columns which mean: number of ID's that matched the physical cylinder and number of ID's that did not match. 5,25" 1.2MB (double side) are 15 sectors/track/head. There are two heads and it should report 30 0 in last columns. For 3,5" 1.44 is 18 sectors/track/head - should be 36.
5. Basically the procedure is as follows: set a motor position, tighten one screw, then press 0, then 1 to reposition header. If you have stable reading, check other tracks in increments of ten (keys 0-8), if not - repeat previous step. The last track for 1.2MB is 79 so don't be surprised if you see question marks on track 80. On every range it should be 30 0 reading on last column. First column shows current track number. If you for example press zero, first column should be zero, if it is not, then the zero sector sensor should be moved back or forth. Do this after you got stable readings on all ranges.
6. If for some reason you got stable readings on range 0-60 but afterwards it drops (to say 20 and changing), then it would mean that the spring that presses on top header may be worn out. You may try to transplant another one or bend it a little bit to make it press harder. Under no circumstances press header directly with your fingers!!! You may scratch the surface and destroy headers. Do not also change header azimuth on top header (there are usually two small screws for it). If you do it, then get yourself an alignment diskette (if you can find one cheap - let me know) and an oscilloscope 😀
7. If everything is set up, try to read image of the disk, there is an option in imd. And make sure you try several floppy disk and all of them read correctly. One of it could potentially be formatted on a drive with misaligned headers, so better check with more samples.
8. This alignment procedure is obviously no match for oscilloscope, but for home use is absolutely ok.
9. If you have bad luck, headers may already be destroyed before you even try to start this procedure and it won't read a thing, only ? is displayed. Chances are swapping header modules from other similar drive would help
Hope it helps. Also make sure that everything is well lubricated and you should be fine. Don't forget about the second screw before the final assembly.
Edit: tip for FreeDOS. There is a known bug in some versions of format.com. After successful formatting sometimes a message 'driver not found' is displayed. A workaround for it is dir b: before issuing format b: /u command. (provided that b: is your floppy, and a: is freedos ramdisk, when booting from thumb drive/cd)