akimmet wrote on 2024-10-04, 01:58:

You can use a high density PS/2 floppy drive on a model 30. The drive will still operate as a double density drive. The system's controller just won't be able to read high density floppies, even though the drive is capable.

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting

Video in here explains how
https://forum.vcfed.org/index.php?threads/ibm … sk-drive.63619/

rmay635703 wrote on 2024-10-04, 22:38:

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting […]
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akimmet wrote on 2024-10-04, 01:58:

You can use a high density PS/2 floppy drive on a model 30. The drive will still operate as a double density drive. The system's controller just won't be able to read high density floppies, even though the drive is capable.

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting

Video in here explains how
https://forum.vcfed.org/index.php?threads/ibm … sk-drive.63619/

Oh nice! Thanks, I'll take a look!

And WRT the power supply, I looked at it again. I incorrectly said the -12 and +5 were shorted to ground.

Really, the +12 and +5 are very low resistance to ground. Not fully shorted, but resistance is in the 10-20 ohm range.

I don't know enough about power supplies to know if that is troubling, or just due to how they work. Is that normal?

I still need to open it up and look for anything suspicious as well.

Alright, back trying to see if this system will work again.

None of the tantalums are currently shorted.
I've got the system completely disassembled.

I'm seeing a short on the motherboard between the P8 power connector (should be +5 V) and ground (P8 pins 5,6, etc.)
However ,the +5 lines on the P9 connector (P9 pins 4,5,6) are NOT shorted to ground.
This occurs with the riser card removed and memory removed (CPU, and ROM chips are still in place).

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?
My board is the P-Planar board.

Guld wrote on 2024-11-17, 21:20:

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?

Look here: https://archive.org/details/ibm-ps-2-model-30 … matics/mode/2up - The P7 connector is on page 1, and as you see, the PS/2 model 30 (8086) is just not XT/AT compatible. That pin is supposed to be grounded.

mkarcher wrote on 2024-11-17, 21:38:

Guld wrote on 2024-11-17, 21:20:

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?

Look here: https://archive.org/details/ibm-ps-2-model-30 … matics/mode/2up - The P7 connector is on page 1, and as you see, the PS/2 model 30 (8086) is just not XT/AT compatible. That pin is supposed to be grounded.

Ah thank you! I wondered if it was the same pinout or not but thought it was. That explains it! Thanks for the link!

Alright, so have slowly worked up to testing the power supply (thread here PS/2 Model 30 (8086) Power Supply Question) and plugging in the motherboard with everything disconnected.

I did pre-emptively replace the 10uF 16V 3 legged tantalums on the +12 and -12 volt lines on the riser board with 10uF 25V 3 legged. Mouser still has them, but they aren't exactly cheap. Part Number Kemet T398E106M025AT https://www.mouser.com/ProductDetail/KEMET/T3 … shyvuRkYg%3D%3D
Link to minuszerodegrees.net site discussing the 3 legged tantalums https://www.minuszerodegrees.net/failure/IBM% … 0capacitors.htm

The battery on the riser board was showing 2.9 volts but I replaced it all the same.
Part Number: BR2/3AE2SP. Want PC Pin (Horizontal 3-Pin) termination.
Mouser part for exact fit https://www.mouser.com/ProductDetail/Panasoni … TlPS3ylEujiY%3D

Everything is working so far. Was able to power on and video was working. Got errors about keyboard, etc. as expected since I didn't have anything plugged in. So far so good.

Do the heads on the hard drive on PS/2 need to be parked? When I first got it, I of course had NO idea if the previous owner would have parked the drive heads or not.

Powered up with memory, floppy and hard disk.

Had some issues with it recognizing all the memory, but after cleaning it seems to be good at 640k now so hopefully that's resolved.

Unsure of floppy drive yet, have to put an image on a 3.5" double density disk first.

Unsure of hard drive (20MB - IBM 72x7568). It spun up, made some noises (never sure if good or bad). Eventually got a boot error.

Have not recapped the hard drive or floppy drive yet, plan to clean the floppy drive and make a boot disk for it. Is IBM DOS 3.3 a good choice for these?

On the hard drive...I had to wonder if the 72X7568 requires parking the heads (as mentioned previously)? I've never had a system that had that "feature", and I have NO idea if the previous owner parked them (I would guess not) or how it may have been treated being moved around before I got it. Or may that particular drive doesn't require that? Any advice on that aspect? I see in the manual where it says you should park the drive, but I also found a thread for a different drive on the model 30 that said it did not need the heads parked.

Any suggestions about how to go forward seeing if I can access the hard drive or possible reformat it, etc.?

Booted to a dos 3.3 floppy this morning. Was actually able to switch to the c drive and see the files. However ran into errors accessing most files.

Did a sys on the c: drive to try to get it to boot off the c: but still get the disk boot error message. Not sure if this could be symptoms of failing caps on the old drive or hopefully not head damage from heads not parked. Not sure how each of those might manifest.

Chkdsk reported errors on fat1 fat2 and then just errors and gave up.

Okay, so I've been working on the hard drive more now. And so far no luck. I have replaced all the electrolytic capacitors. The old one had very high ESRs, anywhere from 30-60 ohms, up to kOhm. No change in behavior after capacitor update.

As noted before, originally, I could view the file contents of the disk but couldn't really run anything. I always got an error and also could not boot from the drive.

Running the ADV diagnostics on the hard drive, it passes the following tests:
write,read,compare
seek test
error detection and correction

However, it fails the "head test" with error 1705 "record not found"

I ran a low level format on the disk "unconditional format" which seemed to complete, and wiped the disk, but when I try to create a new partition in fdisk...the drive just sits with the light on and does nothing for a long period of time. No error messages, just sits.

I ran the surface analysis, and got more errors than I could possibly write down. Some notes:
1) head errors primarily on head 3 and somewhat 2, but I do also see errors from 0 and 1 as well. (rough guess that 99%+ are on head 3)
2) It appears that every cylinder had an error on head 3...hmmm
Not surprisingly, it reports that the "defect threshold has been exceeded" "usable capacity has fallen below 20 MB"

akimmet wrote on 2024-10-04, 16:38:

The early miniature surface mount capacitors used for PS/2 floppy drives and hard drives are well known to fail. Unrestored working examples are exceptionally rare.
Like you noticed, these capacitors rarely exhibit signs of physical leakage. It is almost certain they are bad anyway.

Any ideas what the values are on the surface mount caps? There appear to be a few different sizes and they are obviously not marked. I'm not sure if those could cause the types of issues I'm seeing or not. I find it hard to believe there are so many errors unless head 3 has a serious issue somehow (or the circuit connected to it of course). I'm not as familiar with hard drive circuitry as floppy drives though.

Alright, got another WDI-325Q drive to test with. And was able to determine that the board I replaced the capacitors passes all tests with the new drive. So the drive controller appears to be working well. So the head issue with the old drive may actually be a hardware fault *sigh*. At some point when I can keep it relatively clean I'll try to open it up and take a look. The only other thing I could do was to inspect the ribbon cable with the 12 wires on it (assuming there are 3 connections per "head", read, write, ground). I don't believe there are any issues there.

Guld wrote on 2025-05-04, 17:08:

So the head issue with the old drive may actually be a hardware fault *sigh*.

The PS/2 Model 30 drives (which are a kind of XT-attechment drives, although using a different protocol than the normal Seagate/WD XT-attachement drives) have a reputation to fail quite often (as do other hard drives of that era as well by now), so while it is surely disappointing to be dealing with a faulty hard drive, it's not unexpected.

Yeah, I know, and I have an XTIDE I can use if need be. But the drive sounds really nice when it works!

Any other recommended maintenance on these? I oiled the motor for driving the head position ever so slightly in the hopes it would at least hopefully lengthen how long that part lasts.

The main drive motor looks a bit inaccessible. And I don't want to open one up to poke around at all unless I can't possibly make it any worse 😁