PDA

View Full Version : Quadram flaky disk drive



falter
March 16th, 2014, 10:13 AM
Hey guys,

I have a Quadram expansion unit for my PCJr that I got really cheaply. The second drive needed a little work (needed lubrication) but it seems to write and read ok, but only it's own disks. If I put in a disk from another drive in there, it might read it somewhat but usually starts throwing up data errors. It also will only format disks to 180k.

It is working fine enough for my purposes (I use it as a save game drive) -- I'm assuming we are dealing with an alignment issue, and from what I've read it's not really possible to fix without the proper disks and a scope? Nothing I can try?

mbbrutman
March 16th, 2014, 11:06 AM
I've rarely had a drive that was totally out of alignment. I'd give the rails another full cleaning and lubrication to see if that helps the positioning.

The heads could be dirty - clean those too. Just don't pull or push on them too hard. If it only can format to 180K then one of the heads is really bad or not functional anymore. It might take several cleaning cycles to make progress - use a real cleaning diskette (not Q-tips) to be safe. I use 91% isopropyl alcohol for things like this; the more pure you can get it the better. There are other noxious chemicals you can use; I'm sure ChuckG will chip in with that list.

You might also look for broken wires. The wiring to the heads is hard to inspect but it might be a fault before the heads.

What cleaning technique and chemicals are you using now?

krebizfan
March 16th, 2014, 11:06 AM
What is the model on the second drive? If the original drive in the expansion got swapped with a single sided drive you will only be getting 180kB disks. Not as uncommon as you might think. Some of the Jr related clearances made buying an expansion with floppy drive cheaper than buying the drive alone. Double check the cabling and mounting.

Could you describe what diskettes you are using and what drive created them? Have you tried using the primary (internal to the Jr) floppy to create 180kB floppies to see if the expansion floppy will read them? More information increases probability of finding a solution.

Options:
1) Alignment disk
2) get a different drive

SpidersWeb
March 16th, 2014, 11:11 AM
If DOS is unable to write/read successfully on the second head track 0, it'll revert to a single sided 180K format. Since it formats 180K, that suggests to me that one of your heads is dirty or not working.
This would also cause read errors if you put a 360K formatted floppy in it - since it'll only be able to read one side of the media.

I'd start by cleaning that head.

falter
March 16th, 2014, 05:40 PM
Thanks guys! It appears to read and write ok from a 180k disk formatted and written by the main drive. So I am guessing we have a head problem. I do have a spare drive from the dead Jr it came with, but I'd prefer to keep the original in place because it appears to be the one supplied by Quadram (at least, if the sticker is to be believed).

17800

mbbrutman
March 16th, 2014, 06:14 PM
Quadram never made diskette drives. ;-0

krebizfan
March 16th, 2014, 07:15 PM
Don't be afraid. Open up the Quadram enclosure and tell us what model floppy is installed. You are most likely going to have to open things up anyway to any chance of fixing the problems.

If you are lucky, someone will have already archived a maintenance manual for that drive. It will save hours in determining the exact state of the system.