800k ejecting all the time

[bibilit]

I have a strange issue with a 800k drive, the ejecting motor is spinning all the time.

tried with several motors, the plastic gear is new.

So the issue is on the board, somewhere... the connector is receiving 2 x 12 volts and 1 x ground and the switch is working ok.

Any clue ??

 

[LaPorta]

What machine is this? What cable? Is it original to the machine?

 

[bibilit]

Macintosh Plus, yes original cable.

 

[volvo242gt]

Original drive to the Plus? I seem to remember having the same issue with the floppy drive that came with my last Plus. Eject motor never stopped running. Never figured it out, since, soon afterward, I bought the SE and gave up on the Plus project.

 

[mg.man]

I don't know if it's related, but there are differences in the early Sony 800k drives. Some needed a pin omitted on the floppy cable. There were two types of floppy cables, ones with a "red" (pin 1?) wire and others with a "yellow" (pin 1?) wire. I *think* the yellow wire one had the omitted connection. There was a post or thread that discussed this. If you have a "red" and "yellow" floppy ribbon, try both and see if there's any change.

 

[mg.man]

Some other discussions here :
Post in thread '800k floppy eject motor off the chain!' https://68kmla.org/bb/index.php?threads/800k-floppy-eject-motor-off-the-chain.40403/post-437192
...and here :
Thread 'Angry 800K Sony MP-F51W-23' https://68kmla.org/bb/index.php?threads/angry-800k-sony-mp-f51w-23.37571/

 

[LaPorta]

That was why I was curious if it was the same drive, cable, etc and all that was changed was the eject motor. What was the original issue? When did it start? Is this a new computer to you and it just does this all the time, or a machine you already had with a bad eject motor that you changed out just the motor?

 

[max1zzz]

Have you tried the drive in another mac?
My Plus dose this (And according to my dad has done it intermittently since the late 80's) we always assumed the drive was bad however I later found it worked fine in another mac. Both the drive and cable are original to the plus which suggests this is a logicboard issue in my case

Annother member suggested years ago that the filter networks on the logicboard going bad could cause this but I have never sat down and diagnosed it any further - using a external drive was always easier! (though I have seen these fail and even short between elements so could belive this)

 

[desertrout]

Here are a couple schematics, which might help trace the issue... at least back to pin 25 of the CX-23077A or pin 9 of of the floppy connector -- depending on the drive you have there (as @max1zzz suggests, you might be getting an eject signal on that pin from the Plus instead of it being something of the drive board)

 

[bibilit]

If you have a "red" and "yellow" floppy ribbon, try both and see if there's any change.

I have probably several of each, ok will have a look and see but so far the cable has the red stripe

 

[bibilit]

if i understand the schematics properly the small three wires loom from the drive board goes to the Omron eject motor.

The red wire is negative and directly connected to the motor negative terminal.

The yellow wire is connected to the positive terminal (+ 12v) of the Omron motor but a switch is in between, so only spinning until the switch will kill the + 12 voltage.

On the same + side, the brown wire is also connected to the Omron positive side, through two transitors Q6 which is a NPN one and Q7 which is a PNP.

So for me something is wrong in the brown wire side (either a transistor or the CX23077 chip) hence the Omron receiving the +12 volts when not required (eject command)

 

[ironborn65]

You might want to check the "sensor" that sits close to the eject motor. The contacts might not close the circuit and it believes it never reaches the end, so it keeps spinning.
It happened to me.
Sorry I can not send you a picture right now

 

[bibilit]

the switch is working ok.

no sorry, was checked already before my first post.

tried to fix it this week-end, wasn't able to do so. the eject motor is receiving constantly 12 volts from the bown wire so motor is spinning all the time.

replaced both transistors... don't know at this point what can be wrong, used another Plus for a test, same issue.

 

[flanneljeans]

tried to fix it this week-end, wasn't able to do so. the eject motor is receiving constantly 12 volts from the bown wire so motor is spinning all the time.

replaced both transistors... don't know at this point what can be wrong, used another Plus for a test, same issue.

Did you ever figure out this issue? I have the opposite problem - the eject motor never gets 12 volts on the brown wire to start the eject cycle. If I momentarily jump from the yellow to the brown wire the motor will do the eject cycle so it seems both of our problems are upstream of the eject module.

For your issue, I would have bet that Q7 on the drive board was bad allowing 12 volts through all of the time, but since you replaced it and still have the same problem, I guess it's something else.

I also verified that the eject switch does short out the two motherboard pins when pressed. The problem must be somewhere on the motherboard between the eject switch and the ribbon cable to the drive board. Does that make sense? Any thoughts on how I can debug further?

 

[bigmessowires]

You likely have a "red label" 800K drive. I believe the Mac Plus originally included "black label" drives. If you cut pin 9 on the ribbon cable, your always-ejecting problem will disappear. https://www.bigmessowires.com/2021/08/13/floppy-drive-pin-9-is-not-my-friend/