5 1/4" Floppy Drive Not Reading?

[CuriousMarc]

The plot thickens. I was curious to see if there was some signal at the drive heads, so I partially opened the drive until I could access the head connectors. I eventually found which pin was write of Head 0.

Here is what I got, while using ImageDisk, and forcing formatting at 1.2M (500 kHz rate) green=write gate (my trigger), yellow= write data at the connector, blue=head 0 write signal. Not much signal at the head

But here is the same thing at 360k density (300 kHz rate), plenty of signal at the head

Could it be that I could format and write at 360k? Going back to the DOS prompt, I tried:
FORMAT B: /F:360
It sure worked! Then I can write files to the disk, see the directory, etc... Everything is fine.

Then I tried:
FORMAT B: (formatting to default 1.2M)
It fails with track 0 unreadable. Makes sense since there is no signal going to the write head.

So I can only write at 360k density. But this is a 1.2M drive (Chinon FR-506)! Actually it reads a 1.2MB diskette fine. What gives? Is there another jumper that would cause it only to write at 360k?

Past 2 am now, time to go to bed and mull on the newly acquired knowledge...

Marc

 

[CuriousMarc]

Epilogue 1: the drive was faulty, details of the fault below.

I monitored the pin 2 status (density change), and the disk responds abnormally to it.

When jumper MS1 is on (which I think is auto density), read is fine but write is inverted
- reads correctly at low density when pin 2 is low, and high density when pin 2 is high.
- writes correctly at low density when pin 2 is low, but doesn't write at high density as it should when pin 2 is high

When jumper MS1 is off (which I think is fixed high density), write is fine but read is inverted.
- reads at low density, refuses to read at high density, which is incorrect (should be the opposite).
- writes correctly at high density.

So there is no setting that will make this faulty drive both read AND write at HD. Which is why if fails to format or write an HD diskette, although it can read an already formatted one.

 

[CuriousMarc]

Epilogue 2: Just picked up the exact same 5.25" Chinon FR-506 drive at VCF MidWest this week-end, and this unit works perfectly.

The proper jumper config for this Chinon FR-506 drive on a PC is:
TM - on (termination resistors on)
DS0 - off
DS1 - on (must be jumpered as B: )
DS2 - off
DS3 - off
IU - off (In Use LED front light)
MS1 - on (auto density switch according to Pin2 density select pin)
D-R - on (Disk Change signal)
MS2 - off (Single speed 360 rpm. When on, speed changes between 300 and 360 rpm depending on Pin 2)

 

[CuriousMarc]

Morality: don't trust bits coming off old hardware...

 

[billdeg]

Some of these drive repair tips are very well explained, I think this thread should be cleaned up and made sticky.

Having read this thread, I would have taken the "replace the drive" strategy almost right away for non rare drives like this. Specifically replace with the same drive/model/rev. If not a duplicate at least known working. My logic
1) you can get back to work.
2) A known-working drive will expose problems with the controller/BIOS/cabling so you know you have control over those variables separately from the drive itself.
3) you can fix the bad drive by compare/contrast technique

Downside - You don't learn as much if you never get around to fixing the replaced drive.

 

[mrc333777]

i dont know if any one still reads this, but i was having similar issues with the chinon fr-506 and 2 of the epson sd-600
i was trying to format with format /s /u b: and kept getting errors on the epsons at around 53% and about 83% with the chinon.
i tried many disks used and new of many types, same issues, then finally i opened another box of new disks and they formated perfectly.
i think the problems were the disk types, the ones that worked 100% are on the box printed if this helps anyone.
" BONUS by verbatim high-density minidisks MD2-HD Soft Sectored ".

 

[cj7hawk]

Try degausing the diskettes.... Especially 5.25" disks.

Also, I find a lot of disks will fail formatting due to stepping issues, especially 3.5" worm drive disk drives. Cleaning like crazy, relubricating and running the heads back and forth a lot seems to work. I just use Greaseweasel to run the seek back and forth with a batch file so it seeks to 79 then to 0 then 79 etc, over and over.

It will fail with an error if there's an issue.

Then I clean the heads and let them dry, then try reading and writing again. Also, always check the disks after a new disk is accessed, especially if it had issues ( and check the one before it ) to see if there was any shredding.