MPI floppy drive issues

[smbaker]

I have a couple MPI BR8B2A drives with issues. On both of them I performed a test by writing an image to it and then reading back the image. Screenshots are attached. I'm assuming from this that one drive has one bad head and the other has two bad heads. Am I interpreting that correctly?

The one with two bad heads "sounds bad" while it is spinning. I'm not sure exactly how to describe the sound, but it does not sound smooth, so potentially it's not a case of bad heads but a case of the disk not spinning at a consistent speed. I have disassembled it and I find no play in the bearings.

Are there any particular known issues with MPI drives and their heads?

 

[smbaker]

Also, here's the drive that I'm calling "two bad heads" if I use it to read a known good floppy (as opposed to writing and then reading a floppy):

 

[ldkraemer]

The first thing I see is the RPM is 313 versus 300 RPM.

1. Clean the HEADS...GENTLY with a cotton swab dipped in 91% Alcohol. You are looking for
Brown Oxide that gets deposited on the Head(s) from shedding floppy media.

2. Set the RPM to 300RPM plus or minus 1 RPM.

3. Purchase a bottle of cyclomethane to lubricate the disks right before you use them.
A little on a cotton swab goes a long way. It will be evaporated the next day.
You can put a little on the Head(s) too.

Then try again.

More information here at Posting #15.
https://forum.vcfed.org/index.php?t...rvation-of-floppy-disks.1254903/#post-1470370



Larry

 

[smbaker]

Thanks Larry, I did try cleaning the heads with no success. I didn't see any residue on them.

One thing that became clear to me last night is that I don't completely know what I'm doing here... These are 80 track drives with I believe is 250 Kbps data rate. This is what they commonly call DSQD? I have been using DSHD media with it, and the "known-good" disk that I used with it, I wrote in a HD 5.25 drive. Right now I'm not sure whether my Greaseweazle is treating the MPI as a 250 Kbps drive or a 500 Kbps drive. The image I'm writing as a test image is a 250 Kbps image, so it should be writing it at a 250 Kbps data rate. I think.

The other issue is that from what I read, I should be able to use DSDD media in a DSQD drive. That doesn't work at all. If I write DSDD media and try to read it, there's almost no flux transitions on it.

 

[smbaker]

Turns out the media was a problem. I switched to a NIB 3M DS/DD disk and I was able to get one of the two drives to write and read-back without issue.

Both the DS/HD disk and the brand-unknown disk would not work. Upon inspection the brand-unknown disk I thought was ordinary DS/DD was revealed to have ~ 10 index holes, so I guess I have a lucky find as I could probably use some hard sectored disks.

The second drive is not so lucky. This one had been roughly handled by someone and the motor speed potentiometer had been ripped off the pcboard. I had been swapping the "good" pcboard back and forth between the two drives, but now that I have one good drive, I'm no longer interested in that. I soldered in a new potentiometer, adjusted the speed to 300 RPM, but still that drive is not working right. Whomever beat it up may have done more damage. I may give up on it unless / until the need arises to troubleshoot it more.

 

[ldkraemer]

Yes, the proper media is DS/DD Media that is formatted as 80 Tracks,. You can compare the RPM Feedback
Circuit and compare the good drive to the drive that has problems. It shouldn't take long to find what is going
on.

Larry