Procedure for testing a disk drive that gives "?Boot Error"

[B 9]

As mentioned earlier, the drive in my Z89 had been briefly working great with the hard-sectored disks from Glenn and then it broke mysteriously. 

I tried dismantling it and cleaning the heads, but that did not help. 

Symptom:

Typing `B` at the H: prompt reports "?Boot Error" after about one second, but only if I have an actual boot disk in the drive.
With no disk in the drive, it takes fifteen seconds before the error.

That suggests to me that the disk is reading data and the signal is getting garbled somewhere.

Is there a step-by-step method for determining where the fault is? I do have an oscilloscope if that's necessary.

Thanks,

—B9

[Joseph Travis]

A concern that I have is that the single sided drive uses a small felt pad to apply pressure to the disk, opposite the head.  They can come off quite easily at which point the drive no longer works as intended.  You might verify if it is still there or not.  Good luck!

Joe

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[Glenn Roberts]

Definitely worth checking. Also it could be the disk itself. The disks I sent you are original media so they’re over 40 years old. They all passed the media check when I tested them, but over time and use the oxide will wear. Try creating a new boot disk. In general you will find the reliability of old floppy disks to be low by modern standards. Sooner or later you will experience failures.  For any extended use you will probably want to move to digital media like a Compact Flash-based drive.

Sent from my iPad

On Nov 23, 2025, at 11:24 PM, Joseph Travis <jtravi...@gmail.com> wrote:



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[B 9]

Thanks for the tip. I am familiar with the head load pad from repairing Apple ][ Disk Drives and did check it. The felt was darker than what Apple used, but it was still there and seemed to be in a good shape (cylindrical, not skewed). I didn't measure the amount of pressure nor try the "finger test" where one light pushes on it to see if the signal strength increases (it shouldn't). 

I hadn't thought about bad media since two different disks failed to work (HDOS and LDR). I'm still curious if there are any manuals explaining the test points for the Heathkit hard sector drive controller. I did find some test points for the drive itself in the Siemens FDD 100-5 Maintenance Manual, although several require a "test disk" which I presume is unobtanium these days. 

---B9

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[glenn.f...@gmail.com]

The H8 version of the H17 controller has some useful troubleshooting waveforms (attached).  Not sure if these translate to the ’89 or if there’s something similar??

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[norberto.collado koyado.com]

It applies to the H89 as it is same design.

Get Outlook for iOS

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Sent: Tuesday, November 25, 2025 6:16:20 PM
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Subject: RE: [sebhc] Procedure for testing a disk drive that gives "?Boot Error"

 

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[B9]

Got a chance to look at my Z89's bum drive over the weekend and I have a couple questions.

I disassembled, cleaned, and reassembled the drive controller card. It didn't fix it, but I am now curious why one chip was oddly corroded, U811, a 74LS132N. (See picture). It seemed okay when I tested it out of circuit. Is that part corroding a known issue? What would cause that to happen to all the pins on a single chip? (All the other chips are fine).

I tried transferring disk images over the serial port using H89LDR and it did let me save to new floppy disks, but they also fail to boot. From the MTR I can use V (view memory) and see that data is being read in from the disk. For example, in the case of trying to boot from a saved copy of H89LDR2, the code actually looks correct. Even though MTR said there was an error, I'm able to use G to successfully launch the program.

Is there some sort of checksum MTR does before transferring control to a loaded program?

Thanks,

--b9

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[Joseph Travis]

The "corrosion" you are seeing there is tarnish on the silver plated pins of the IC.  This is quite common with TI branded ICs.  It is easily removed using Tarn-X in an ultrasonic cleaner.

Unfortunately, H89LDR doesn't perform a verify after write (or any verification for that matter).  It is likely that the floppy / floppies you're using are degraded.

BR,

Joe

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[glenn.f...@gmail.com]

The silver oxide is conductive but not as conductive as the original silver plating. Fortunately it will only form in areas exposed to air.  It looks ugly but is not necessarily an issue. I usually just clean it off with a fiberglass brush pen (e.g. https://a.co/d/6nwZ7vM) , but Joe’s approach (ultrasonic cleaner) should make it look like new if you’ve got one.

 

You say you cleaned the controller card but what about the drive?  Mechanical components (especially 40-year old ones) are usually the first thing to suspect. Apologies if you already did this and mentioned in a previous post – hard to keep track….

 

The disks I sent you are indeed old and certainly to be suspected, however they did all pass media testing so I would hope at least a few are still OK.  Nevertheless old disks will usually fail when you least expect it.

 

One of the disks I sent is the one that has the saved H89LDR program on track 0.  From your description I think you’re saying that when you boot that you get an error that drops you into the monitor, however when you examine the code in RAM it looks right and you are able to execute it via the G monitor command?

 

Unfortunately we don’t have any stand-alone disk/disk drive test programs.  They all run under an operating system so you have to have a bootable system in order to test the drive(s) ☹

 

Remind me if you’ve tuned up the drive (cleaned/oiled the bearings and stepper mechanism).  If not, that’s the next step.

 

Do you have any other old 5.25” drives?  Any original “PC” (DS/DD/48TPI) drive should be usable.

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