TRS-80 Model 3 - Upper Drive Can't Read/Write

[phil.bischof]

I have a TRS-80 Model III (recently acquired) and the lower drive works just fine. I can boot with TRSDOS boot disk no problem. However, when I try to put a disk into the upper drive and list a directory, it tries to, but just keeps moving the head out and back, out and back. It does this 5-10 times and then just fails with ERROR 04.

I am guessing there is something with the alignment? Can anyone think of some things I can try to remedy this? I would really love to get this machine working.

Below is a link to video showing the current problem. In the video, you can see and hear the head moving back and forth. I'm stumped. I've cleaned the head, lubed the rails, tightened the "head split-band" screw, followed several tutorials on things to try and no luck. I do not have an oscilloscope.

Watch 20240324_210244[1] | Streamable

Watch "20240324_210244[1]" on Streamable.

streamable.com

Thank you!!

 

[Patrick.B (TTR)]

Out of alignment is possible, but in my experience more often than not it is one of two things;
The TRS-80 model 3 drives are single-sided with the read/write head on the bottom of the diskette and a felt pad on the top to counter pressure the head "holding" the media flat on the head. this felt is often "worn/gone" with time.
The other possible issue is often if not the felt pad, is the disk drive motherboard may have a faulty component (and yes that usually requires an oscilloscope)

Side note: the drive was never designed to have the rails "oiled/lubricated" if they are catchy they should be sanded with 3-4000 grit wet sandpaper to remove all accumulated corrosion bringing them back to their original "shine"
the why is the plastic carrier that slides on the metal rail "scrapes" back and forth and an oil or lubricant may alleviate the issue of inconsistent travel, in time it will, in the end only provide yet another reason for issues.