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MPI 360k won't read/write

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.
 
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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:

20190810_114120.jpg

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.

https://youtu.be/vyPrCBEU_Us
 
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.
Dwight
 
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.
 
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Ah, that clears things up! You don't have a head-load solenoid!

See the bottom closeup near the spindle motor on my drives:
mpi_bottom.jpg

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.
Dwight
 
I'm pretty certain that the drive uses the same head suspension that the 5x series uses--the casting is the same and the connectors appear to be the same.

So, here's the MPI 51 drive manual.

My guess is that at some point, someone tried to clean the heads a bit too aggressively and deformed the suspension. It should be possible to bring it back to operation.
 
No, there's nothing on the leftmost 2 pins of the large red connector in your 2nd photo. You definitely don't have a HL solenoid.

Your photo betrays the problem you're having. Both photos show that the spring sheet metal head support has been distorted on the right side (looking toward the back of the drive), which means that the head isn't making good contact on that side.

If you remove the head and sheet metal spring and try to straighten in, you'll very likely mess up the alignment, as you suspect. It might be possible to get the thing working halfway by bending the coil spring lead (using 2 pairs of long-nosed pliers to exert slightly more force on the head. This isn't great for disks, but it might work in a pinch.

So, it seems to me that you've got two options--fix the sheet metal spring and struggle with realigning or do a half-a**ed fix that might be good enough for now.

If Dwight has any better ideas, I'm open to suggestions.
 
Chuck(G) said:
No, there's nothing on the leftmost 2 pins of the large red connector in your 2nd photo. You definitely don't have a HL solenoid.

Your photo betrays the problem you're having. Both photos show that the spring sheet metal head support has been distorted on the right side (looking toward the back of the drive), which means that the head isn't making good contact on that side.

If you remove the head and sheet metal spring and try to straighten in, you'll very likely mess up the alignment, as you suspect. It might be possible to get the thing working halfway by bending the coil spring lead (using 2 pairs of long-nosed pliers to exert slightly more force on the head. This isn't great for disks, but it might work in a pinch.

So, it seems to me that you've got two options--fix the sheet metal spring and struggle with realigning or do a half-a**ed fix that might be good enough for now.

If Dwight has any better ideas, I'm open to suggestions.
Click to expand...

I was thinking of maybe affixing a small weight of some kind to the head armature. Or something like plasticine on the head 'tent'. Just enough to get it there?

I don't know how good the alignment is. When I got this drive, it did not work (probably was always bent like that). This was many, probably 15 years ago when I knew a lot less than I do now. I'm sure I made things worse by playing with the resistor trimmers above and goodness knows what else. I'm shocked the thing actually can read anything at all. So we might be clinging to an alignment that isn't any good.. unless by some fluke it is actually aligned properly with the head weighted down.
 
Well, if you fancy that you can handle alignment issues, the best repair is to remove the head assembly and straighten that spring. Be sure to mark reference lines on the parts, however, so you stand a chance of getting things right again.

Doubtless the head azimuth will be off, but as long as it's close, you'll be okay.
 
While we're on the subject of MPI 5x drives, if you look at the PCB on the front left side of this photo:

360k-micro-peripherals-inc-model-52sa_1_59c06cef189bd61ed86fb641b754c766.jpg


You'll see a row of holes for a 10-position header. Ever wonder what it's for? It takes a small plug-on PCB with a 9602 dual monostable, some capacitors, a trimmer and a couple of resistors. It generates a READY/ signal based on the index interval.

MPI PCBs varied quite a bit. My 5x for 100 tpi has a huge stepper, about 2¼" in diameter.
 
The best way to make a mark is to use a small triangular file and make a notch towards the back on either side. It would cut into the square washer, spring and base. Having them on both sides would help getting it right.
I was right that the spring hinge looked a little wanky.
Dwight
 
Let me follow up by saying that if you work with metal at all, one of these is an inexpensive addition to your toolkit. Your local big-box or hardware store usually has them--they can scribe glass as well.

If you're of the inclination to drill holes in metal, an automatic center punch is an essential tool that will give you an accurate starting "dimple" for your drill. I also use one to set wirewrap pins.
 
I've got one of those. The advantage of the file is that you can insert the file to get best alignment. From past experience, scribing across three surfaces, with one being a thin spring is a little on the tough side.
Dwight
 
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