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TI External Disk Drive Questions


horizon2374

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Recently acquired a TI PHP1850 External Drive (SS/SD). Came with original cables, adapter board, etc. I was able to get the drive working, the motor sounded very rough but after few attempts it seemed to work. But my plan was to upgrade it to a DS/DD drive as I have the Corcomp controller with an existing DS/DD drive in PE box. I acquired a similar drive to the one in PE box (these are both Micro Peripherals MPI 52 S). I can access the drive, light comes on, disk is rotating, but nothing is read. Ran disk cleaner as well, no luck. But here’s the thing… I can initialize the disk - it will go through the process correctly (stepper motor running correctly) up until the point it is to read the boot sector/file directory, and then it comes up with the error code.

 

Drive 1:

As you can see in first pic, HS, DS 0, and HM are jumpered (this is Drive 1 which works correctly). Whether it has a resistor pack or not it still works the same. If I remove the HM pin (first pin on the left) drive won’t be recognized.

 

Drive 2:

Second pic shows similar setup (HS, DS 0 jumpered) with HM pin open. If I connect a pin to HM (similar to drive 1) it won’t be recognized.

 

Pic 3 shows the full cable connection.

Pic 4 shows the adapter card connection.

Pic 5 shows cable connection to Corcomp controller.

 

The adapter card is correctly assigning Drive 2 as it should be without having to move the jumper manually.

 

Any thoughts on how to fix this boot sector / file directory problem? Could this just be a faulty drive? I really wanted this to work since it matches the other drive in the setup.

 

 Thank you!

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One note, based on the physical jumpers, your Drive 0 (1) does NOT have HS jumpered. Look carefully and you will see that the center of the strap seems to have been cut. I just looked in the manual at page 3-2 for the usage of these drive shunts. A drive should use HS or HM, but not both at the same time, which is why Drive 1 (2) stops working when you add HM. I suspect your current problem is actually partly due to the way you have Drive 0 (1) selected, which works fine if you only have one drive in the system. Using the HM shunt turns on the solenoid for the drive whenever the motor is turned on--and all drive motors are turned on at the same time, so you may now have the solenoids on both drives pulling down the write current when you try to select drive 1 (2). It is generally not a good idea to have the heads selected using different means on different drives. I pulled open one of my original TI MPI-51 drives to verify that the default TI shunt settings were what I remembered them to be, and they were: Jumpers for HS and DS0 are the standard settings used by the TI, so do not use HM. If you don't have any of the purpose-built shunts with the right configuration, you can just bridge the two necessary shunts with clipped-off resistor or capacitor leads. . .as long as they fit snugly into the dual-wipe socket, you should never have any problems there (I have drives that I have used that way for much of the last 40 years). Here's the MPI 51/52 manual for you. Disk Chuckers rule!

 

Actually, if you do some creative positioning with the jumper blocks you do have, you can set them properly in your Drive 0 (1). Move the shunt connecting the pins for DS0 to HS (with the current HS pins hanging over the board and not in the socket) and then move the shunt on HM to the DS0 pins and you should be good to go. . .and your setup would actually require a termination resistor in both drives, as each drive is on a different connector on the disk controller. Your Drive 0 (1) is on the internal connector (the 34-pin header connector) and your Drive 1 (2) is on the IDE connector at the back of the card. A configuration like this is the only time you need two termination resistors (and if you have multiple drives on each connector, then just the last drive of each chain needs one).

micro-peripherals-model-51-52-flexible-disk-drive-manual.pdf

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Thank you! You have better eyes than I do! 🤣 I followed your directions, and moved the pins on the shunt pack. This fixed an issue I was having with drive 2 turned off, drive 1 motor would keep running and couldn’t be accessed. 😊

 

Unfortunately drive 2 still isn’t cataloging the disk or reading/writing the boot sector/file directory. For testing purposes I tried hooking the drive to the internal cable and it still wouldn’t work (confirms this is not an external cable issue).

 

So the drive needs to be repaired or try a different one.

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1 hour ago, horizon2374 said:

Thank you! You have better eyes than I do! 🤣 I followed your directions, and moved the pins on the shunt pack. This fixed an issue I was having with drive 2 turned off, drive 1 motor would keep running and couldn’t be accessed. 😊

 

Unfortunately drive 2 still isn’t cataloging the disk or reading/writing the boot sector/file directory. For testing purposes I tried hooking the drive to the internal cable and it still wouldn’t work (confirms this is not an external cable issue).

 

So the drive needs to be repaired or try a different one.

if you haven't cleaned and lubricated the drive, you probably should try that first

 

the rails the heads move on especially need to be cleaned and lubricated properly

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Thanks yes I cleaned the heads extensively and lubricated the rails. The stepper motor is functioning properly, as, oddly enough, the drive will perform an initialize of the disk but will fail when it finishes the operation since now it is looking for the boot sector / root directory. The drive needs to be repaired, not sure how or what to do but could be some type of adjustment. Easy to say just replace the drive but they are hard to come by, go for a sizable amount of money, and most of them are untested.

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You might want to look at the drive belt on your disk chucker to make sure it isn't slipping. You know that several portions of the disk drive are working: the sensor for the disk timing hole, the stepper motor, and the motor circuit. You also know the drive selection circuitry is correct, since it is doing all of the above mentioned things when you try to select it. If the belt is deteriorated/slipping, it may just not be finding the initialized sector zero to write the header information to. Another note: there is a timing wheel on the spindle--these sometimes fall off over time (I have a drive like that). The drive doesn't use it for normal operations, but it is used to calibrate things.

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  • 4 weeks later...

Current Setup:

- Corcomp DS/DD Controller

- MPI Micro Peripherals 52S drive (internal)

 

I've given up! I even bought another drive from eBay (Magnetic Peripherals BR8B1A), and same results (will format drive but no boot sector read).

 

Drives I've tried with external connection:

- MPI Micro Peripherals 51

- MPI Micro Peripherals 52

- Magnetic Peripherals BR8B1A

 

None work correctly. I thought maybe it was the controller on the external side causing issue - but when I tried to connect them to internal connection, same result.

 

Next step would be 2 half-heights (Matsushita?) with custom drill holes. I do have an internal drive cable that will work with 2 drives (connect to internal drive connection on Corcomp controller), but would need power Y-cable.

 

It's been a tiring project though - think I'm gonna stick with the single drive!

 

Unless someone can send me drives that are known to work!! Hahahaha. Aesthetics are important to me - nice-looking, matching, beige colored drives with red LED lights would be perfect. 😉

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Is someone able to test your drives and cables in their system, if you post them off? Maybe your card as well with their known working drives. Three faulty drives sounds a bit suspicious. You're not trying to use a high density floppy by any chance - don't think that will work.

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