• Please review our updated Terms and Rules here

Weird Tandon TM-100-2A issues

N

nztdm

Experienced Member
Joined
Mar 17, 2018
Messages
180
Location
New Zealand
I am currently trying to get two floppy drives working properly for an IBM 5150.
They both seem to mostly work after head cleaning and rail greasing. Both are spinning at 300rpm.

The issues are that they fail to read/write randomly between track 30 and 40 (both heads), and on track 0 head 0.
This seems oddly specific and consistent; especially the track 0 part. Maybe just a software issue. Testing with Checkit.

One drive seems to fare much better than the other, as seen in the following two screenshots:

View attachment 49959 View attachment 49960

The floppies are brand new 3M DS,DD ones. They aren't perfect, but seem in better shape than other new disks I've acquired in the past. Some have a faint splotchyness visible on the cookie in random locations in the right lighting.
The ones I tested format and work 100% in a Compaq Portable II's slim 5.25" drive. Formatting with DOS, read testing with Checkit.

I can fill the disk with files on the Compaq drive, or on the Tandon drives, supposedly successfully.
They read back fine on the Compaq, but often have 1 or 2 files fail on the Tandons.

If I made a boot disk with FORMAT A: /S, I can boot from it with both drives. This suggests it can read track 0 head 0?

The consistency of the failing reads in Checkit suggest the heads are fine. Maybe capacitors on the PCB need replacing? Original vintage tantalums.

Here's one drive. The other (which has less errors), is a green PCB. Both have '84 chips. Both have "IBM" on the front bezel.
View attachment 49961

Testing with a 1982 IBM 5150 floppy controller card. When I test with a 90's multi-I/O card, there are less errors but some are still there and in the same region. This suggests some sort of digital signal integrity issue? Unless the 1982 floppy controller is simply bad as an entirely separate issue to the floppy drives.

Any ideas what else to try?
 
Check to see that the positioner band is tight on the stepper capstan and that the capstan itself is firmly attached.

Not doubting what you stated, but is the 300 RPM with a floppy inserted or with an empty drive?
 
I have had good results with inconsistent Tandon 100 series drives by lubricating the stepper motor. I put the drive on it's side and use a small amount of WD-40 pooled around the center shaft of the stepper. After a few moments I flip the drive on it's other side and repeat the procedure on the opposite side of the stepper. This has repaired a number of Tandon floopy drives of mine. I do this to any drive I acquire that has that type of stepper motor (the old 3.5" Tandon/Western Digital hard drives for instance).
 
Could it be inconsistent wiring to the read heads due to fatigue? If you can write a full disk on the Tandon and verify all is well on the Compaq, and the Tandon is struggling to read a specific areas, it could indicate the read cabling has gone funky due to fatigue or some other defect. That track position just happens to be the point where the wiring disconnects. Maybe connect an ohm-ranged multimeter to the head.. headers, slowly move them through their full range of motion and see if you get dropouts on the meter?
 
I'd try the drive on a completely different machine, not just with a different controller card.
 
Thanks everyone.

After testing the drives in another machine, they both worked perfectly. Including the original floppy controller.

I wonder what was wrong in the other machine. Maybe the power supply is noisy.
 
You must log in or register to reply here.
Back
Top