Troubleshooting and salvaging data from a non working MFM drive?

[JonnyGators]

I acquired a non-working ComputerLand BC88. It's a bit crusty and rusty, but many of the parts in it have tested as working, although the power supply is dead.

My main interest in acquiring the machine was checking the contents of the MFM drive, to see if software that came packaged with the BC88 was still present. Although the hard drive powers up and makes typical hard drive noise, I've not been able to get it to work.

My attempts to use the drive have been from another working ComputerLand BC88, so the same PC type as it came out of.

Given that I'm using the controller, cables, and drive together as they were, in the same model machine they came out of, I'm working under the assumption that everything is configured as it was when it was last working. (But it wouldn't hurt to double check or verify any configurations that could cause the results I'm getting).

Here's info from the drive label:


I have confirmed the controller and cables do work with a known good hard drive. But when connecting this drive, I get a 1701 error when booting.

On another thread where I mentioned this, modem7 recommended using the RAYXTMFM tool. Output below:


I also ran the tool with the known good drive connected, to check if the controller reset test would pass with a good drive. It does, as can be seen below:


Here is a picture of the controller:





Are there any options for further troubleshooting?

 

[djg]

Ready is a signal on the 34 pin connector. You can verify that it is high indicating drive is saying its not ready. Pin 1 on the 20 pin cable should be low when the drive is selected.

Also check drive had terminator resistor installed and correct drive select jumper.

Micropolis 1325 have know problems with a deteriorating rubber head stop that prevents the heads from moving. Do you hear seeking when the drive powers on? The 1323 may have similar issues.

RD53 Disk Drive Repair

 

[Chuck(G)]

80h status says that the drive isn't coming ready. How are the jumpers on the drive set?

 

[JonnyGators]

Jumpers look correct.



It has jumpers on W1, W2, and DS1

Documentation here https://www.micropolis.com/support/hard-drives/1323 suggests this is the configuration it would have come with, and to move the jumper from DS1 to DS2 for AT, but I'm using it on an XT so I believe this configuration is consistent with how I'm using it, and seems to support my theory that it's configured as it was when it was last working. But do let me know if something looks off in that picture, I don't always know what I'm looking at.

I'm not sure about the sounds, or what it's supposed to sound like, it does spin up and make noise, and continues to spin make noise while the computer is powered on. Will have to do more research and listening.

 

[Chuck(G)]

DS1 depends on the cable (twisted, or flat). See: https://minuszerodegrees.net/ibm_xebec/ibm_xebec_cabling_info.htm

 

[JonnyGators]

It's using flat.

 

[modem7]

Micropolis 1325 have know problems with a deteriorating rubber head stop that prevents the heads from moving. Do you hear seeking when the drive powers on? The 1323 may have similar issues.

That is a certainly a possibility for the drive not becoming ready, because I expect that after the drive's self-test sees the spindle come up-to-speed, the self test will then step the heads on and off cylinder 0 to see if head stepping is occurring.

 

[JonnyGators]

I opened up the drive to observe what was happening and try pressing on the spot pointed to in the picture from the shared link.

What I found is that when powered on, the drive spins up, the heads unlock, never move on their own, but can move freely when pressing the spot on the picture.

I don't believe the heads are stuck, but I do believe that whatever mechanism is supposed to be moving the heads, isn't working.

Not sure if there's much hope beyond this point, unless someone wanted to work on repairing a mechanical issue on an old hard drive with unknown data that is likely to not be of much value. I suspect if I tried to dig in much further from this part it would just be a dissection that would damage things beyond repair. But if someone out there likes working on drives, and loves a good mystery, it's up for grabs, so long as I can get a copy of whatever data is retrieved from it.

 

[JonnyGators]

Here's a little live stream of the drive opened up.

 

[modem7]

I don't believe the heads are stuck, but I do believe that whatever mechanism is supposed to be moving the heads, isn't working.

Or maybe the drive's self test is failing early.
If I, in the day, had been tasked with writing the self test code for an MFM/RLL hard drive, the gist of it may have been something like the following.

Step 1: Test CPU/MPU. If this subtest fails, simply halt the self test.
Step 2: Verify checksum of CPU/MPU code ROM. If not as expected, simply halt the self test.
Step 3: Test RAM buffer. If this subtest fails, simply halt the self test.
Step 4: See if spindle rotating (via index sensor). If not rotating, simply halt the self test.
Step 5: Wait a certain period of time for spindle/platters to get up-to-speed. If not up-to-speed after that timeout period, something is wrong; halt the self test.

At this time, platters are up-to-speed (i.e. heads no longer contacting platter surface and at required height). It is now 'safe' to move the heads.

Step 6: If track 0 (cylinder 0) switch not activated, step heads out until the track 0 switch activates. If still not activated after [drive's cylinder count] steps, simply halt the self test.

At this time, heads indicated (via switch) as being on track 0.

Step 7: Step in 5 times (i.e. heads expected to then be over track 5)
Step 8: Verify that the track 0 switch is no longer activated. If not as expected, simply halt the self test.
Step 9: Step out 5 times (i.e. heads expected to then be over track 0)
Step 10: Verify that the track 0 switch is activated. If not as expected, simply halt the self test.

At this time, the track 0 switch (and related circuitry) is verified as working.

Step 11: LONG SEEK - Repeat steps 7 to 10, but instead of track 5, go to the last track. On failure, simply halt the self test.

Self test successful. Whenever the controller 'selects' me, indicate 'drive ready' (unless something subsequent goes wrong, e.g. spindle speed drops below spec).

Although, if I could control the drive's front panel LED via the self test software, I would flash an error code indicative of which subtest failed.

 

[SomeGuy]

I wouldn't rule out the possibility of a faulty logic board (or boards). That is at least something that could be replaced if a suitable replacement board could be acquired.

It still would be good to know what the Ready logic line is outputting (the controller error is not always definitive), but from the video it does not look like the drive is becoming "ready". I don't specifically know how this model should behave.

Given that is a servo rather than a stepper based drive, that makes things more complicated. The drive could be spinning down for a lot of different reasons. Motor not getting to a stable speed, not reading servo information, the logic board not powering the motors properly, and so on.