There's a low-level format utility on one of the diskettes shipped with the computer.
The diskettes are probably easy to find, but if not, I have them somewhere...

There may be another problem, though - floppy drives on those machines are notorious for failing.
Does yours work?
And keep in mind it's a 720 KB drive.

eheh - no it doesn't! 😀 Discovered after my previous post.

Well - I am not 100% sure I am writing the disk right - as you say it's 720K so took me a while to hopefully write a correct copy of DOS 3.3 - but it does not read. The disk spins, the head barely moves. I moved the head manually a bit (to make sure the motor is not shaft) and it goes back to track zero when it post.
I'll research on that drive, if you have any pointers or ideas, I am all ears! 😀

Thank you!

About that floppy drive: I fixed one of those drives some years ago, see Let's fix some PS/2 floppy drives! . It's a common theme that electrolytics in those drives are gone by now. I am very confident that at the position of C1 on the motor PCB, a multilayer ceramic cap of 1µF (even the cheapest version) will do just fine as replacement, and live basically forever.

@mkarcher

Amazing! I'll continue there then! Thank you!

Back to the HDD, THIS might have something to do with the fault. It's the ribbon cable going to the heads I reckon. It's all corroded. I am not sure that that's the issue though as it feels to me that the head stepper motor is stuck - or the heads are stuck.
But this cannot be good! 😀

I cleaned and re-seated all the connectors but still same issue unfortunately.

tony359 wrote on 2022-12-16, 17:45:

Back to the HDD, THIS might have something to do with the fault. It's the ribbon cable going to the heads I reckon. It's all corroded. I am not sure that that's the issue though as it feels to me that the head stepper motor is stuck - or the heads are stuck.

If the platters spin up, the heads are not stuck to the platters. That's one positive thing at least. There are drives that have an electomechanic interlock on the stepper: The operating voltage actuates an electomagnet that removes a spring-loaded blocking mechanism. A mechanism like this is used to lock the heads in the parking area while the drive is used. I don't know whether the PS/2 model 30 drive contains a mechanism like that, but a lot of drives at that time did. In essence, it might be fine that the stepper motor is stuck while there is no power, and it is also fine that the stepper motor is hard to move while the power is applied, as the power is used to keep the stepper in the position that it is supposed to hold. Nevertheless, you should be able to turn the stepper motor while power is applied with a moderate amount of force.

It is a common fault for hard drives that the grease of the bearings of the head stepper motor degrades and seizes the motor. It's so common that oiling a hard drive stepper motor is part of the YouTube intro of the well-known retro-channel "Adrians Digital Basement" on YouTube. Applying a drop of high-quality machine oil (like sewing machine oil or watchmaker's oil) to the axle of the stepper motor is generally a good idea.

I am very familiar with that intro of course! I am not sure my stepper motor has an accessible spindle though - I'll disassemble and take pictures. I did not try to move the stepper - my observation is only based on the noise I hear - that is, I don't hear much movement. It could be that the stepper is not properly driven of course - something I will need to check with an oscilloscope.

Indeed the fact that the platters are spinning is a good sign 😀

Here is a video showing the issue. After trying to power up, the drive blinks its LED 4 times (I noticed that it changes number of blinks when I turned it on with a cable unintentionally disconnected so there must be a meaning there).

https://www.youtube.com/watch?v=TK7p6RURT9I

tony359 wrote on 2022-12-16, 18:35:

I did not try to move the stepper - my observation is only based on the noise I hear - that is, I don't hear much movement.

Listening to the sound of the drive, I don't think that drive still uses the old stepper technology, it sounds more like modern voice-coil operated head that bangs against some mechanical stop. It might be a broken track zero sensor, if the drive still has something like that.

tony359 wrote on 2022-12-16, 18:35:

Here is a video showing the issue. After trying to power up, the drive blinks its LED 4 times (I noticed that it changes number of blinks when I turned it on with a cable unintentionally disconnected so there must be a meaning there).

The hard drives in the model 30 8086 are a variation of XT IDE drive[1], which means the drive itself has a microcontroller. The slow blinking you observe at power-up is normal, you can compare it to this power-up video of a HDD equipped model 30: https://youtu.be/61UbTmlTWSU?t=344 . I count three normal slow cycles and then a quick double blink. This double blink could be an error code emitted in the drive power-up sequence. You see that in the "reference video" the fourth blink is also shorter than the first three cycles, but it's a single one.

I guess you are right that there is some issue related to head positioning, and the double blink is an error code indicating "positioning system failed, giving up".

Footnote:
1: I'm not talking about the modern XT-IDE interface card, and I am also not talking about the XT-IDE BIOS that has been developed for that card, and is widely used in the retro community as enhanced IDE BIOS even in AT-class computers. Instead, I'm talking about "classic" XT IDE (aka XTA), as described here: https://www.dosdays.co.uk/topics/xt_ide_vs_ide.php . Of course, IBM being IBM designed a proprietary connector including power instead of the standard XTA configuration, so the pinout on that page is of no help for you. The IBM PS/2 technical reference for the PS/2 model 25 or 30 includes the IBM pinout, should you be interested in it.

Apologies for not showing you the full sequence. After trying two times (after I lift the microphone), the drive gives up, the system gives error 1701 and the drive starts blinking 4 times - pause - 4 times - pause forever. When I unintentionally unplugged the speed sensor the blinking was three times.

When I removed the PCB to inspect, I saw a "Step-syn" (I think) where I'd expect the head stepper to be - so I am assuming there is a stepper here. Top left on my picture. I see a screw, maybe I can remove that lid and access the spindle? I will have to check that the coils are still working and being driven somehow.

And yes, I have cleaned a bit of that horrible dirt - will fully clean it at a later stage 😀

Thanks for your help so far.

tony359 wrote on 2022-12-16, 20:02:

When I removed the PCB to inspect, I saw a "Step-syn" (I think) where I'd expect the head stepper to be - so I am assuming there is a stepper here.

Yes indeed. This is a 2-phase bipolar stepper motor, so I was wrong when I suspected a voice-coil drive. It has two coils, and each of the coils should have a resistance of 11 ohms. You should be able to measure continuity at the 4-pin plug connected the motor.

Thanks! I cannot wait to hear that familiar squeaky noise of that stepper motor! 😀 Finger crossed I can revive it!

I have a feeling many of you might have seen this already but just in case, here is the first part of the repair!

https://www.youtube.com/watch?v=_hpE7lNLODw

I'm resuming this thread as I am working on the PS/2 again.

Re-seating and cleaning the RAM did not help. Removing the RAM (so leaving the 128KB on the MoBo) gets rid of the memory error.
So either I have faulty modules (2x256KB, 30pin) or something's wrong with the board. I'm learning that IBM used custom IBM modules, not standard. So either I modify standard 30pin modules or I try to source some.

My concern is that without "known good modules" I might end up in a loop. What if the modded/purchased modules still don't work? Do I blame the board or my mod/new modules?

I'm looking for ideas and confirmation that the Model 30-8086 indeed uses non-standard memory modules. If I compare the IBM schematics, the pinout is identical to a standard 30pin RAM I found online (attached). So I am a bit confused.

These are the ones currently installed. I don't even know if these are IBM, they came with the machine but for what I know they could be random non-IBM modules 😀

Answering to my own question: it turned out IBM used standard SIMM modules on the 8086 version - the modified version started with the 286. So mine are just standard SIMM modules - thankfully 😀

I made a first video repair for this PS/2!

https://www.youtube.com/watch?v=x0zQYWQsnz0

Looks like my PS/2 "needs" a BIOS update. the ICs show 61X8940/61X8939 and Ardent Tool shows a later version. Just for fun, is there a way to display the BIOS version on screen?

Part 3 of my repair journey! 😀

https://youtu.be/pHqJnSNobT0

It's taken a while but... final part is out! Also my DOScember video!

I've managed to discover what exact fault the floppy drive has and the case goes through a full restoration (LOTS of rust!!!)

https://youtu.be/adkIx0iO5dY

Hi, I saw your latest video, and I wanted to compliment you on the excellent work, maybe I skipped the previous videos, and I missed the details on the HD repair, but what matters is the end result, and from what I've seen , the PC is back in working order.
Until 2009 I also had an identical PC, unfortunately a family member of mine gave it as a gift, it was complete with monitor and the rest is the same as yours, perhaps the disk was 20 MB, and the RAM 1 MB, but I don't remember exactly if it was like this.
I have a decent collection of PCs, ranging from 286 to i5, I'm only missing the Athlon slot A, and all the server sockets, I repaired many of them myself, but I have several waiting to be repaired these days I would like to see if I can fix at least one 486, I have three to fix, I don't know anything about two (purchased to test), one had a problem, after a certain time (not always the same) it stops.
In short, I hope to have luck with at least one, I would like the 486 PCI, but the 486 OLB (Opti Local Bus) wouldn't be bad either.
If you want to see the images you can find them here:
Re: Test and troubleshoot PC@LIVE motherboards