HyperDrive 20 troubleshooting

[JeffC]

Well, I unexpectedly picked up a 512k with an internal HyperDrive 20 yesterday. Per the serial number decoder, the machine started life as a 128k in March '84. It currently has 512k ram and an 800k floppy drive, so I assume it has been upgraded to a 512ke, though I haven't taken the logic board out yet. The machine boots fine with a floppy.

The downside is the internal HD isn't working, the drive doesn't spin up or make any noise. I measured voltage going to the drive, and it has 13.2v and 5v. There is a red LED on the front of the drive (not the front of the machine, on the drive, buried in the enclosure) that blinks 3 times slowly, and then 4 or 5 times very rapidly, and repeats this pattern over and over. Does anyone have any experience with these types of drives? Can they be brought back to life? I've done a little bit of searching, including a very old thread from @JDW , and I know it's not a SCSI drive, but I'm not sure what the options are at this point. Any input would be much appreciated!

I apologize for the not-so-great photos, I haven't dug any further into the machine yet.

 

[JeffC]

I pulled out the drive to take a look at it, it's a MiniScribe 8425. I have a lot of respect for the engineers that managed to shoehorn this whole setup into the Mac case, there is a lot going on in there.

 

[JeffC]

I did a bit more work on it this morning. I took the PCB off and was able to turn the spindle by hand, it did seem a little tight at first. I turned it by hand for a few minutes and put it back, no luck, the drive didn't spin up. I did it a couple more times, same result. There is a connector in one of the photos that I put a red rectangle around, that connector looks to run from the PCB down to the motor that turns the spindle. I checked voltage at that connector, the three pins on the left (brown, yellow, red) all had 13.2v, the other three didn't show anything, maybe grounds? This suggests to me there is power going to the motor, so I think it's not a good sign the drive won't spin.

The other definitely-not-good thing I noticed is the two small components in the corner by the blue connecter seem to have catastrophically failed, as seen in the photos. I wouldn't think that would stop the motor from spinning though as long as it's getting power, which it seems to be.

I'm not quite sure where to go with it from here. I imagine I could get a PCB from another drive, but if the drive itself won't spin up, that's an issue. I haven't yet looked into whether there is a utility out there that could low-level format a replacement drive so the HyperDrive would work with it. A really quick google search shows there are a couple devices that emulate MFM drives and use and SD card, though I have not looked into those, and maybe there would be formatting issues involved there as well.

 

[JeffC]

I just ran across a thread on a different forum where someone successfully used a MFM emulator to get their HyperDrive working. At about $200 it's not cheap, but it is probably worth it to preserve a piece of Mac history. Used MiniScribe 8425 drives aren't cheap, and there's no guarantee one of those would work, or for how long.

 

[fehervaria]

These disks are amazing, but after 30 years they can have lot of problems.
First of all, your disk is reparable - in my opinion from far - based on the pictures. The burned out component possible to see on the high resolution picture on Wikipedia's page, the component is the C12 capacitor:

https://upload.wikimedia.org/wikipedia/commons/1/13/MiniScribe-Model-8425-PCBA-05AA-4.jpg

File:MiniScribe-Model-8425-5.jpg - Wikimedia Commons

commons.wikimedia.org

Here you can find lot of information what the hard disk does after power on:

M8425 / MINISCRIBE Jumper Festplatten, Controller, Hard Disks, Layouts, Jumpersettings, Utilities, Daten! 5900 HDDs

To maintenance the physical parts, first of all lubricate the stepper motor's shaft adding only a drop of fine mechanic oil.
The Miniscribe 8425 has no stiction like the Quantum disks but the read/write heads could stick on the plate because of the long standing. To "release" the heads from the plate, in the power on moment have to kick it to go. A little beat on the shorten end of the disk housing. Don't hammer hardly, just a tiny little "kick"...

But first you need to change the C12...
Good luck, I hope you can give new life to this vintage emblem.

 

[JeffC]

Thanks for the detailed reply! I took the PCB off and was able to turn the spindle, it rotates freely. When I first turned it I don't recall feeling any "extra" resistance, the heads definitely weren't firmly stuck. I rotated the spindle by hand for a couple minutes hoping that would get it turning freely, before I noticed the damage to the PCB.

I've attached a couple photos of the front and back of the damaged area. I mirrored the back so it's easier to compare the two. Unfortunately my microscope isn't great quality, but you can see the resistor burned rather badly. It looks to me like it burned the via(s) out of the board. If this were a single or double layer board I could run some bodge wires, but dealing with a multi-layer board (which I think this is) is beyond my skillset, especially without a schematic. Ideally I could just find a working PCB to put in and hopefully that would get the drive functioning, but unfortunately the cheapest 8425s on eBay are around $50, with no guarantee the PCB is sound.

That's where the project stands at the moment. I'm not quite sure of the path forward, but one way or the other, either with a working HD or the MFM emulator, this HyperDrive will live again!

 

[JeffC]

I ran across this video yesterday, a guy has a SCSI MiniScribe 8425 that also had a resistor and capacitor next to each other burn. I'm not sure if there is any relation between the SCSI and IDE boards, but I thought it was interesting.

 

[LeadedSolder]

I finally figured out that my SE FDHD wasn't starting ("flupping," or the PSU going into protection) because of the MiniScribe 8425SA that came with it. I followed my nose until I isolated it as the source of the burned component(s). For some reason, possibly stubbornness, I want to try and figure out what's on this drive.

For me, C3 is burned/exploded (appears to be a 22µF tantalum) as is R1 (0.5Ω 1/2W resistor, maybe a current shunt?) and R45 (unknown but says DALE on it, hard to remove because the Molex power connector is blocking one of the legs; I'll have to desolder that first.)

I pulled R1 today and measured it and it seems to be about 0.7~0.8Ω on my cheap multimeter, so I put it back in even though it's cracked and burned.

I tried to glob on a through-hole 22µF electrolytic in place of the blown tantalum at C3 to test with, but I don't have any that are small enough to fit back into the case (C3 overlaps with one of the mounting bracket ears.) I'll order a tantalum from Digi-Key (75 cents! yikes) and see if I can manage to spin the drive up or if I'll just make more expensive smoke. C3 was definitely shorted, though – single-digit ohm resistance across the terminals.

All of these seem to be related to the +12V line, which (after removing C3) has a 33Ω resistance to ground. There are two other through-hole resistors on this line that look a little burned – R44 and another one nearby – but they're not nearly as bad and also appear to be just "regular" resistors unlike R1 and R45, which look special to me.

I also dripped a little bit of 3-in-1 oil into the head stepper although I haven't worked up the courage to try and turn it by hand (there's a scary sticker nearby saying DO NOT ROTATE INTERRUPTER.)

I haven't watched that YouTube video yet, mostly because I'm super excited that at least someone else has had this problem and wanted to dash off this reply with my pictures of passive gore. I have had temperamental tantalums in the past; I wonder if this one is just not up to spec anymore and couldn't handle the inrush of trying to push a rusted-stuck motor.

edit: Yep, sure looks like the same problem. Obviously I have a different board – my burned resistor is far away, but this gives me something to go on.

 

[JeffC]

Great thanks for the info, please do update as you work on the drive! I actually just got a Miniscribe 8425 working yesterday, unrelated to the one I talk about further up, this is a SCSI version out of an SE. It was having trouble seeking and wouldn't boot, the stepper motor would just go back and forth and make unpleasant sounds. I put two drops of Super Lube PTFE oil on the shaft of the stepper motor, and after it worked itself back and forth a few times, the drive started working just fine.

 

[LeadedSolder]

Not much to add other than I desoldered/destroyed the Molex connector so I could get at both of the joints for the visibly burned R45 resistor. It's a DALE-branded 1Ω 1% resistor, and I'm guessing it's meant to be a pretty expensive precision part. It looks like the same part from the Hack Shack YouTube video, so I've put it in my Digi-Key cart along with a replacement 22µF tantalum capacitor (I decided on 25V just to be on the safer side.)

The stepper has been sitting vertically to let the the 3-in-1 oil soak in since yesterday, I'm tempted to add more but I suspect there's only so much it will allow before bad things start to happen. Still not sure if I should try to turn it by hand: the "do not rotate interrupter" warning is scary, but also I suspect that warning is more for if the heads weren't parked before the drive turned off.

 

[retr01]

Hi @JeffC! How is it going with the HyperDrive 20 in your beloved Mac 512k? Were you able to get it fixed and running?

 

[retr01]

I found this advertisement back in the day by General Computer. They marketed and produced the internal HyperDrive 20 for the Mac 512k. The ad was on pages 90 and 91 of MacUser magazine's premier October 1985 issue.

 

[JeffC]

Hi @JeffC! How is it going with the HyperDrive 20 in your beloved Mac 512k? Were you able to get it fixed and running?

No updates yet, it's been moved to the back burner for the moment. I really need to get my hands on a working IDE MiniScribe 8425 or equivalent, I know a guy who may have something but I probably can't get to his place for a month or two.

Those drives on eBay are close to $100 and sold as-is. I could justify $100 for a working drive, but not for a gamble. I was considering buying a MFM drive emulator for a bit over $200, but I'd really like to have a spinning platter drive in this machine, and that's a lot of money to get it not quite how I'd like it. But that's my standby.

So the project is on hold, but not forgotten!

 

[LeadedSolder]

Small update, a little disappointing but at least there is some progress on my sickly 8425SA.

The RetroHackShack video helped a lot on figuring out what was going on. Thanks a lot for the help!

I replaced the burned resistor at R45 (1Ω, 1%) but I had to chop up the Molex power connector to get at one of the solder joints for it – desoldering would have taken too long. It measured 26Ω out of circuit, which makes me suspect the "precision" part of "precision resistor" does not really exist anymore.

I then replaced the blown tantalum capacitor at C3 (22µF, unknown voltage so I just went with 25V) and the Molex connector. Resistance across +12V and GND went up by a lot at this point, which is a good sign.

After several weeks of daily watering with 3-in-1 oil, I was finally able to move the stepper motor shaft by hand. A little more oil got it moving fairly smoothly. I suspect I should have used something with a bit of edge to it, like Marvel Mystery Oil, but I had never used that directly on bearings and I was not in an especially big rush. A precision oiler helped get it into the right spot.

I decided to grab the crappiest ATX supply I had on the shelf and set it up to run the MiniScribe drive without any data cable attached. It spun up, sounded about the worst I've ever heard a hard drive, and then stopped after a few seconds. It clearly wasn't running at the full 3,600 rpm and made more noise than feeding a sheep to a garage door opener. Here, listen for yourself:

I gave it a few minutes to cool down and then reset the power, which made it spin up again and keep running for a little while longer, until I lost my nerve and shut it off:

This was still super loud, so I decamped to the garage, where it would be further away from sleeping toddlers. I gave it a half-hour test, with the hope that an Italian tune-up would help things. The noise persisted, but slowly got better with runtime (see? I am right sometimes.) It became a lot better when I set the drive on its side, and now it sounds like a very loud regular ol' 80s hard drive, as opposed to a pile of crap.

During this extended test, no stepper motor action was heard or seen. I did notice some discoloured traces leading from the STMicro PBL3717A motor driver IC to what I assume is the drive pin for the stepper motor; no doubt caused by trying to force it when it was rusted shut. Not sure if that would also kill the driver IC, which is obviously NLA. It has zero ohm continuity between the driver pin and the stepper motor pin, so the trace is probably alright at room temperature. The ATX supply is perfectly happy driving this thing all day long, with no measured sag on the 12V rail.

Luckily for me, the MiniScribe has some self-diagnostics, although I haven't yet tried to set the jumper for "test mode" out of fear that it will accidentally wipe the drive. It does have a blink code that arises if the drive is unhappy on regular startup, though. It bloody well ought to; this thing has a Hitachi 6303 microcontroller on board and a full, socketed, DIP EPROM. I've got whole computers on the shelf that have less grunt than this hard drive does.

When I made an LED test harness to connect to the LED pins on the drive, I got on ON-FLASH-FLASH-FLASH error code, corresponding to 0b1000 (or $8) which the manual says:

Code 8 - Unable to uncover Track Zero sensor

This makes some sense if it can't move the stepper motor; however the same code emerges no matter where I move the stepper by hand before starting the drive. I'm guessing there's some ferrous crap lying right in front of the pickup for it, inside the stepper motor, and the sensor thinks that the stepper is permanently stuck at track zero. Still, you'd think it would at least try to move it before raising such a complaint. This makes me think that the stepper drive is also bad somehow, and maybe the badness is contagious.

Not sure where to go next, but I might see if I can figure out what the various pins for the stepper motor do. I also noticed these burned-looking resistors, but for some reason only a little bit of the end of the plastic got scorched:

TLDR, current candidates:

1. Stepper motor driver IC is bad (there's two, so I could swap them, but I'm not clear on what the other one does)
2. Motor is still too stuck for the drive circuitry to overpower it (could try to figure out how to drive it by shorting it)
3. The suspicious R44, R46 precision resistors on the other side of the board (shown above) are also bad. These appear (from colours: purple-green-silver-gold) to be 0.75Ω 5% and they have a little bit of heat damage to the outside, but otherwise seem to be intact
4. One of the transistors underneath the (socketed!) hybrid has clearly been running super hot and actually melted part of the hybrid's conformal coating. The hybrid gets super hot immediately as well, which is possibly intended, since it's stuck into free-flow air and the MiniScribe manual goes to specific lengths to tell you to make sure the airflow is unobstructed onto the board.

The struggle continues. I sure hope this drive has something cool on it after all this.