ATARI 810 reads only first track

[atari_thomas]

Hi there,

 

I have an ATARI 810 drive issue - it only reads the first track of a disk, if you try to boot:

 

I turn on my drive - the head moves correctly on the rails to it's starting position - I insert a DOS disk and turn on my Atari 800XL.

The drive starts and it reads the 18 sectors from the first track - I hear 18 beeps.

Then, the step motor on the right tries to move the head to the next track (track #2 ?) but fails.

 

Repeat

{

The head shakes a little bit, but remains on the original first track.

}

Until [Turn_Off_Drive]

 

I already cleaned the head, I cleaned and put some oil onto the rails.

When the drive is turned off, I can move the head on the rails and when I turn it on, the head is positioned correctly by the drive onto track #1.

I already cleaned all socketed ICs and all plugs.

Yesterday, all of a sudden it worked for 10 minutes, after I pulled off and reattached some connectors.

 

But now I have the same issue permanently.

Anyone has an idea?

 

Thomas

[+bob1200xl]

Try formatting a disk on the drive. See if you can read that disk on another drive.

 

The 810 does not know where track 0 is - it just drives the head back far enough to hit the stop and uses that as the location of track 0. When it seeks from track 0 to track 1, it steps one track. This gives you two independent alignment parameters, the track 0 stop and the stepper motor adjustment.

 

It sounds like you can reset yourself to track 0 but the stepper motor is not aligned to track 1. It isn't quite that simple, but if you can format a disk that cannot be read on another drive, you most likely have a head alignment problem.

 

I would guess that the drive worked for a while when you actually got to track 1 - once that happens the drive usually doesn't need to run back into the crash stop since it knows where it is.

 

Probably the track 0 stop adjustment.

 

Bob

[atari_thomas]

I think you're right.

 

I have two different types of 810 drives. The 'normal' ones (with the button on the front door) and one with a kind of lever as closing mechanism.

The latter has a screw in the drive, next to the drive's head, probably to adjust the track 0 position.

When I turned on the drive the head moved to this position and hit (the screw?) pretty hardly with a loud noise.

I turned back that screw a little bit and that hitting sound got less noisy.

 

Next, I attached a 1050 drive as drive #1 and the 'problematic' 810 as drive #2.

I booted DOS2.5 from the 1050 (D1:), put an empty disk into the 810 (D2:) and formatted it.

Worked fine, without any error. I wrote DOS onto that disk, removed the 1050 and booted up from that 'new' disk from the 810 (D1:).

Worked perfectly, too.

Now I can read format, write and read disks again.

 

Unfortunately I experienced today, that one of my disks, formatted and written on this 810 was not readable on another 810 drive.

But ... as you wrote ... looks like an alignment issue.

[+bob1200xl]

OK - it is an alignment problem. If you have no alignment disks and a scope, you can 'fool with it' and get it to work.

 

Get a speed measuring program - one that reads one sector over and over that was written/formatted on a known, good drive. Gently push the head while it is reading one way or the other. You are plenty strong enough to push the head completely off track, so take it easy. If the read starts failing easier one way that the other, move the head in the OPPOSITE direction just a tiny bit. When the read fails in both directions with the same force, you should be OK - the head is on-track.

 

Now, turn the screw that sets track 0 in one direction until the drive 'misses' track 0. Then turn it in the other direction until it fails again. Turn the screw half-way back. Put a little pressure in both directions on the head while it seeks track 0. Try it with other disks. Set the screw where it seems to work best. It should not touch the head...

 

These procedures are, of necessity, a poor way to do these adjustments. If you have the disks, s/w and tools, the 810 service manual has excellent instructions. Otherwise, do the best you can. If you 'hack' a fix, be cautious about formatting any disks on this drive.

 

Bob

[atari_thomas]

Thanks! I still have another dozen '810' in my collection to fix and will see if that helps. I have the '810 diagnostic cartridge' and a speed measuring program.