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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 17th Sep 2018, 8:35 pm   #21
Dave Moll
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Default Re: IBM PS/2 seems to have got stuck!

I look forward to hearing how you get on with your new PSU when it arrives.
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Old 17th Sep 2018, 11:34 pm   #22
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Default Re: IBM PS/2 seems to have got stuck!

Unfortunately there is also a 8086 version of the model 30 as well as the 286 version you have. I am pretty certain that 61X8574 is the p/n for the 8086 version power supply, 27F4166 is definitely the correct psu for a model 30-286. The power supplies are also slightly different shapes and the power switch link rods (from front panel on/off toggle to the power switch on the psu) are also different lengths. I suspect the connectors are also different. Given the scarcity of replacement parts I wouldn't risk fitting the wrong PSU.

There is a seller on Ebay offering 27F4166, they are listed as being for an 8555 not an 8530 but don't be put off, I have checked and 27F4166 is also the correct psu for an 8555 (PS/2 mod 55sx which is the same physical size as a 8530 but is a 386sx microchannel machine).

My brain may unearth more information overnight, if so I'll update this thread in the morning.

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Old 18th Sep 2018, 9:11 pm   #23
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Default Re: IBM PS/2 seems to have got stuck!

Thanks for your advice. I have feeling you are going to be right. From looking at the internet there seems to be two versions of the IBM PS/2 8530 with two different PSUs? Can this get any more complicated?
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Old 18th Sep 2018, 10:40 pm   #24
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Default Re: IBM PS/2 seems to have got stuck!

Having had time to wind up my brain I now remember that many years ago in order to save time I replaced a faulty model 30 8086 system board with a 286 system board (that happened to be to hand) only to find that I also needed to fit a new power supply!

Yes, sorry, you really do need a 27F4166 not the 61X8574 that you have ordered. Perhaps you can return the unwanted one for a refund?

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Old 19th Sep 2018, 5:37 am   #25
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Default Re: IBM PS/2 seems to have got stuck!

Yes you are right. I found a useful manual with the different models and part numbers. It includes two versions of the PS/2 8530 on pages 227 and 229, the 30 and the 30-286, each with it's own PSU.

http://ps-2.kev009.com/ohlandl/books/ps2-hmm.pdf

Oh well I'm learning more about my computer.
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Old 19th Sep 2018, 11:48 am   #26
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Default Re: IBM PS/2 seems to have got stuck!

Just to say we shouldn't be getting too carried away with this being the PSU. It's still possible a working-fine PSU is crowbarring because it's detecting a fault related to the load (i.e. the motherboard).

This all started when Ontopoftheworld moved the PC remember.

Try checking all the chips which are socketed are seated properly. Is the CPU in a socket or soldered in? Visually inspect the motherboard using a magnifying glass and good light (at an angle to cast shadows) to see if there are any cracks or suspicious looking solder joints (check both sides). Also check there is no damage to any of the wires from the PSU.
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Old 19th Sep 2018, 4:35 pm   #27
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Default Re: IBM PS/2 seems to have got stuck!

What happens if you switch on and then immediately keep pressing the reset button? I had a PC which always switched off after two seconds but if I pressed reset every second it stayed on. Of course it never booted because it was always reset but it did show that the power supply was OK and that something in the POST routine which was never reached if it was always reset was shutting it down.
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Old 19th Sep 2018, 5:10 pm   #28
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Default Re: IBM PS/2 seems to have got stuck!

So, I found the IBM service manual

http://ps-2.kev009.com/ohlandl/books/ps2-hmm.pdf

Says the PSU is 27f4166.

There's also a power connector pinout. So far as I can see there is no means for the motherboard to signal the PSU that something is wrong, so the PSU should run with nothing connected to its connector and the voltages on it can be checked. Pin 1 is the "Power Good" line which the PSU signals *to* the motherboard that it is okay for it to start.

So try just turning on the PSU with nothing connected to it, and in theory if it keeps running it is okay, and if it doesn't it is defective. Pin 1 should switch to 5V within a very short time of switching on.

Also, do just check that it is set to 230V.
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Old 19th Sep 2018, 6:26 pm   #29
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Default Re: IBM PS/2 seems to have got stuck!

Quote:
Originally Posted by IanBland View Post
Pin 1 should switch to 5V within a very short time of switching on.
If pin 1 doesn't go to +5V then the motherboard, and any other device that monitors the pin 1 'Power Good' signal, will refuse to boot.
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Old 19th Sep 2018, 10:22 pm   #30
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Default Re: IBM PS/2 seems to have got stuck!

Quote:
Originally Posted by bluepilot View Post
What happens if you switch on and then immediately keep pressing the reset button?
Alas the PS/2 model 30 doesn't have a reset button, just a power on switch

Quote:
Originally Posted by IanBland View Post
So try just turning on the PSU with nothing connected to it, and in theory if it keeps running it is okay, and if it doesn't it is defective. Pin 1 should switch to 5V within a very short time of switching on.
While I can't be 100% certain with this specific power supply, many IBM switch mode power supplies will not produce an output without some kind of load connected so trying to measure the voltages with it disconnected from the systemboard may well be futile.

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Old 19th Sep 2018, 11:14 pm   #31
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Default Re: IBM PS/2 seems to have got stuck!

Thanks for your comments, really useful to hear.

Yes this all happened when I gently moved the computer while it was on. I have to admit it was standing vertical at the time (maybe not the best way to keep an old computer). I suspect this dislodged some dust and fluff in the PSU which then caused some damage landing on live components. The movement was only gentle so wouldn't have physically damaged the motherboard, but I will give it a good check over,

The PSU when not connected only works for a few seconds and then cuts out.

The only way this is going to be resolved is by trying another PSU, the 27f4166.
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Old 20th Sep 2018, 9:04 am   #32
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Default Re: IBM PS/2 seems to have got stuck!

If the PSU needs a load, then you can try just plugging in the hard disk drive power. Back in the day when I used to repair PCs (not PS/2, so I'm not 100% sure it is the same), this was the 'quick and dirty' test I used when confronted with a dead machine. If the PSU powers up, then it will confirm a faulty motherboard (or another device connected normally to the PSU).

Last edited by GrahamN; 20th Sep 2018 at 9:05 am. Reason: added
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Old 20th Sep 2018, 5:08 pm   #33
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Default Re: IBM PS/2 seems to have got stuck!

Unfortunately, being a PS/2, it's quite possible that the hard disk has the power and signal connectors on a single edge connector. There probably isn't the conventional 4 pin power connector.
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Old 20th Sep 2018, 5:15 pm   #34
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Default Re: IBM PS/2 seems to have got stuck!

Ah - I wondered if the PS/2 may be different. Unfortunately too new a technology from when I repaired PCs!
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Old 20th Sep 2018, 5:23 pm   #35
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Default Re: IBM PS/2 seems to have got stuck!

I've never worked on them either. I have the 'Hardware Interface Technical Reference' on my shelf, but unlike the row of PC-family technical reference manuals next to it, the PS/2 one contains very little detailed information (no circuit diagrams or BIOS source listings, for example).

I could probably find the pinouts for the various hard disk drives, which might indicate whether or not it has a separate power connector but have no idea what is used in this machine.
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Old 20th Sep 2018, 7:37 pm   #36
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Default Re: IBM PS/2 seems to have got stuck!

I once had a PS/1. It wasn't microchannel, but it did have single connector drives.
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Old 20th Sep 2018, 10:18 pm   #37
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Default Re: IBM PS/2 seems to have got stuck!

I've ordered the 27f4166 version of the PSU, so taken a gamble that it's the PSU and not the motherboard that is faulty. The hard drive doesn't have the usual 4 pin plug, so it doesn't give me the option to test PSU supplying power to that on it's own. This is a tricky computer to maintain - I've learnt to understand what propriety parts means!
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Old 20th Sep 2018, 11:41 pm   #38
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Default Re: IBM PS/2 seems to have got stuck!

From memory all models of PS/2 employed drives with a single (combined power & interface) connector. The only exceptions were the later high end models when fitted with the optional SCSI drives, so plugging just the hard drive in to check the PSU was usually impossible.

Quote:
Originally Posted by Ontopoftheworld View Post
I've ordered the 27f4166 version of the PSU
Back when the PS/2 was current technology if I came across a PS/2 with the symptoms you describe, after a cursory check that it was nothing silly then I would have replaced the PSU and expected that to fix it. I admit the passage of many years wear & tear does mean that previously unseen component failures can arise but if this was my machine today then I would still replace the power supply first. The model 30 does not have any side ventilation slots cut into the case so running it standing vertical is unlikely to be an issue.

I should perhaps explain that I started at IBM in the late 1970's and spent close on 40 years as a field engineer. By the time the PS/2 arrived on the scene the personal computer was well established both within IBM and at customers so exposure to their 'features' was rather inevitable especially for those of us who were keen to get involved in anything that looked vaguely interesting. This was further encouraged when we all received free copies of OS/2 Warp!

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Old 21st Sep 2018, 10:21 pm   #39
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Default Re: IBM PS/2 seems to have got stuck!

Wow 40 years, all the changes you would have seen. It must have been fun, all that new development coming over the horizon? Things must seem relatively static now?

There's been a small development. I received in the post the 61X8574 PSU which I mistakenly ordered, and that starts on it's own without being connected to the computer. As my old 27F4166 only starts for a few seconds even when disconnected from the computer would seem to suggest the PSU not the motherboard is the problem Fingers crossed for the new 27F4166 when it arrives!
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Old 22nd Sep 2018, 8:00 am   #40
Dave Moll
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Default Re: IBM PS/2 seems to have got stuck!

Sounds hopeful. Let's hope your next delivery gets you back up and running.
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