810 Drive Mechanism Repair Help

[KLund1]

I have 3 810's all showing the same issues. After power up, with a disk inserted, the head resets to center. When booted the head moved out and starts reading the first track (DOS 2.0s). It them moves up a track then I get the buuurrrpppp sound and it tries to reread the track, and repeats.

I have tested all the side cards, and the card on top. All test good in other 810's. Since the drive spins, LED's lite, heads move, I am assuming the power board is ok.

So thing only thing left is the mechanism itself. One drive had a loose hexnut around the stepper motor. I tightened it so that when the head is at the center, it matches nut position of other working 810's. The next 810 did not have the top pressure pad pressing on the disk. It was about 1/4" over the disk. I bent the spring so that it feels like other 810's, and give light pressure to the top of the disk. The third 810 will not advance past the first track on boot.

I have cleaned the heads, lubed the head tracks. Yes the disk is good in other 810's

What to check/fix?

Thanks

 

[AtariGeezer]

The 810's like to have the head aligned every now and then. Loosen up the hex nut around the stepper motor (you should be able to move the head slightly while keeping the hex nut still using an allen wrench). Put in a formatted floppy with dos and turn on your A8 (allen wrench removed). You can put slight pressure on the head with your finger pushing it toward you. If it reads continuing track, then just tighten up that hex nut where it is.. If not, you might have to move the head a bit more...

[+bob1200xl]

The stepper circuitry does not have an absolute way to determine where the head is sitting at any one time. So, the drive powers on and seeks the head back against the stop. This is track zero by definition. Unfortunately, the track center on the stepper may not match the 'track center' of the track zero stop. The result may be that the diskette can be read on the track zero center and not the stepper center. You can read the first track and not any of the others. Or, you can read all the other tracks but fail on track zero.

 

As I remember, you need to center the heads on track zero with the stop screw and then adjust the stepper for track center. You should use an alignment disk and scope if you want good interchangeability between drives.

 

The manual has all the specifics.

 

Bob

[KLund1]

Thanks bob1200xl and AtariGeezer.

I got one drive working with your advice!

The other two drives are push button type drives. They have vertical mounted steppers. The hex nuts were very hard to loosen. This makes me think that these were never off for track zero.

On one drive I was able to get the motor spindle loose from the round part with the strap wrapped around it. I moved it just a hair, and re-tightened it. Now the drive head will not reset at all from any position along the track when powered up.

 

The other drive, the motor spindle will not let go after the nut is loosened. I could force it, but that seems a bit extreme.

Next suggestions?

Thanks

[_The Doctor__]

Don't forget the 810 normally is just fine the pin connector going from board to board need to be cleaned and re inserted a couple of times...

 

people often do a zillion things and re align and blah blah, I have always did the clean and reseat... the drives were always fine... this happens when they sit..

they don't go out of alignment sitting doing nothing... the oxidation and corrosion at the connectors and chips throws the electronics off and affects it all, clean and re seat everything first then exercise the drives. after all that then get to doing all that alignment and etc etc...

 

so clean and re seat de oxit is your friend as is an aero duster to blow out all dirt and dust that may be in sensor slits and grooves for track zero etc...

 

Never needed to align a drive I put away working yet, just the the ole clean and re seat has been needed and of course the odd capacitor that dried out and died

Edited September 14, 2018 by _The Doctor__

[KLund1]

Thanks,

But as posted above. The side cards, top card, and power board are all good. tested good in two other 810's. SO the mechanism itself is not right. The same with the other 2 bad drives.

Any additional thoughts

[_The Doctor__]

well aside from alignment, you can use an old IR detector or crappy camera/cell phone to try and see if the infrared emitters are working or measure with dmm that they are showing in the track zero and write protect points of the circuit (block unblock) milivolts/volts at that part of the circuitry

Edited September 18, 2018 by _The Doctor__