Forum etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.

Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.

Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.

Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.

"PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.

Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.

Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.

New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.

Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

MPI 360k won't read/write

  • Filter
  • Time
  • Show
Clear All
new posts

    My MPI-51 has shunt 1G that selects which signal (Motor ON or Drive SELECT) loads the head by picking the Solenoid.

    7 jumpered to 8 is Motor ON
    1 jumpered to 14 is Deive Select

    If your drive has Shunt 1G check what is selected.


    Last edited by ldkraemer; August 9, 2019, 01:15 PM.


      So am I understanding that there is a solenoid that should pull the top head down?

      Larry where would I find this shunt?


        My Shunt "1G" is on the Logic Board of my MPI-51 Floppy.

        What is the Model Number of your Floppy. Perhaps I can find a Schematic of it.



          Originally posted by falter View Post
          So am I understanding that there is a solenoid that should pull the top head down?

          Larry where would I find this shunt?
          You should be able to hear the solenoid when accessing the drive. Listen while accessing A: and then B:. The solenoid will activate on attempting to read, and then when it releases the head load at the end of the disk operation.


            The control signals are inverted signals. You should be able to ground the select and/or the headload pin to enable the solenoid. I'd still like a picture of the area of the spring. It may not be important but it may show some issue.


              All of that--I'll also add that on most 5.25" floppy drives, the head-load solenoid was an option and can usually be removed easily if you want traditional 5.25" operation (i.e. your system turns the motor on and off). If you have a system that keeps the motor running all the time, the head-load is a nice feature to reduce wear--but the code has to allow for head settling time. When writing drivers for the early Micropolis drives, I initially made the mistake of not allowing about 15 msec for head "bounce" to die down. Reads worked flawlessly, but every once in awhile, I'd write garbage because the head was still bouncing when the write gate was turned on.

              If you head-load is tied to the motor on signal, there's a built-in delay waiting for the motor to come up to speed that masks the head bounce. But if your system ties head-load to drive select, be very careful to make sure that the driver expects that.
              Last edited by Chuck(G); August 10, 2019, 08:26 AM.


                Hoping this picture helps. I don't usually use the forum for pics as it does weird things (like flipping the wrong way) or making things too small to really see.. but here is the area:


                This is a video of it doing a directory. I don't have three hands so I can't show me punching that in, but basically when it starts turning is when I've hit Enter on Dir B. It fails with a General Failure error. If I put some weight on the top head.. it'll read just fine.



                  Perchance, does the CDC 9409 drive match pretty closely with yours? See section 12 for configuration. You'll want the head-load with motor jumper.
                  Last edited by Chuck(G); August 10, 2019, 11:18 AM.


                    I hear a clink but see no movement. Also the right leaf spring looks a little wanky ( don't mess with it now ). I'm wondering if this drive lowers the top head with the door but lifts the bottom head with the head load solenoid. I don't see any actuator for the top head. With the disk out of the way, you should be able to actuate the head load armature with your finger. Don't close the door while doing this as you don't want the heads to touch without a disk in the way. It can damage the heads. The head load usually makes more of a thunk and not a tiny tink.
                    Can we see a similar picture with the disk out of the way, maybe looking in from the right side at a slight angle.


                      For what it's worth, I'm sitting here with an MPI 54 FH drive (albeit the 100 tpi version) and the HL solenoid is located just forward of the spindle motor. When not actuated, there's an L-shaped sheet metal arm attached to the solenoid armature that pushes up on the head assembly. If someone unfamiliar with servicing these drives tries to remove the solenoid the wrong way or otherwise messes things up, that sheet metal can get bent upwards, so that the head never loads.

                      Instead of pushing down on the head, try pushing down on the solenoid armature. That should provide you with a hint of what to look at. If the bracket clears the head assembly, that is, if it doesn't exert upward force when the armature is depressed, it isn't the head-load mechanism that's fouling you up and you can scratch that off your list.
                      Last edited by Chuck(G); August 10, 2019, 01:48 PM.


                        Here is a couple more pictures:





                          What's on the other side of the drive, down just in front of the blue spindle motor?


                            Here are pics I hope answer that:





                              Ah, that clears things up! You don't have a head-load solenoid!

                              See the bottom closeup near the spindle motor on my drives:

                              See the screw and the peg through the holes that in your drive are empty? Those mount the head-load solenoid. I also suspect that the last two contacts on the P4.1 plug (the long one; the contacts nearest the power connector) are empty. On models with head-load, there would be green and black wires connected that go to the HL solenoid.


                                So, it would seem that this drive doesn't use a head load relay. It would seem we are looking at a mechanical issue and not a head load solenoid. Since we are not getting a picture of the other end, I have to ask about that coil spring. There should be a tail on the other side of the spring pointing down. Is that tail there? Can you remove the board to take a picture of that part of the drive? It might help to get a good picture if you slide the head assembly forward as well.