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interalia
November 11th, 2013, 01:29 PM
Hello All

After sucessfully fixing my 5150 motherboard (a blown tant cap) a few months ago I felt confident to drag out the loft at the weekend a faulty PS/2 50Z (8550) I have had for a few years.

When I first got it applying power did nothing until I pulled the HD disk and it then would start up with a 165 error. Ok I thought get a copy of the ref disk and away you go. But no, the floppy drive that had never felt much good (the floppy disk didn't really want to stay in) would not read the ref disk. Undaunted I got another PS/2 1.44mb drive off eBay but it had a different connecter presentation at the end so gave up and I shoved it all away in the loft until now.

On Saturday I had another look at the floppy drives and realised that I could swap the lower PCB edge connector over the between the two drives (a fiddly job getting the ribbons under the board connected again!). I clicked in place the 'new' floppy dirve and in went the ref disk and it WORKED, the blue IBM conf screen came up, did it's ADF business, finished and I hit enter to restart but just at the moment of restart... POW! CRACKLE! a bunch of sparks and stinky smoke from the PSU from just behind on the power switch... So near yet so far..

I guess it probably had a PSU problem when I got it for two reasons: a) The load from the HD being plugged in wouldn't let it boot. b) Looking at the PSU out of the case there is evidence that some chump has tried to use a non-security TORX to open the PSU and rounded off virtually all of them except the six in the middle. I who has the correct security TORX Bit wasn't very pleased by this...

So my first question is: If I go through the pain of drilling out the screws (my JML screw extractor didn't work like it does on the shopping channel!) am I likely to get away with just cap replacements or is this likely terminal for the somewhat weedy 94W PSU?

The system unit is what I guess is standard spec of 286-10, 1Mb RAM, 30Mb (ESDI?) HD and 1.44 floppy. I have a 287 to go in it and I was planning to get an MCA LAN card to connect to my Netware 3.12 setup.

Second question is: Will a correctly functioning 94W PSU actually be able to run a LAN card and 287 in addition to the standard spec?

Regards

Neil

Surrey, UK

PeterNC
November 11th, 2013, 03:07 PM
My suggestion would be to buy another 8550 and cannabalize to build one working unit. Good luck. :)

modem7
November 12th, 2013, 01:30 AM
I guess it probably had a PSU problem when I got it for two reasons: a) The load from the HD being plugged in wouldn't let it boot.
But maybe the hard drive has a short circuit in it, activating the overload protection in the power supply.


So my first question is: If I go through the pain of drilling out the screws (my JML screw extractor didn't work like it does on the shopping channel!) am I likely to get away with just cap replacements or is this likely terminal for the somewhat weedy 94W PSU?
"Weedy" ? The hard drive could have a short in it, and a component failing in a very old power supply is not unexpected.


Second question is: Will a correctly functioning 94W PSU actually be able to run a LAN card and 287 in addition to the standard spec?
IBM would have spec'ed the power supply to cater for a full complement of options (hard drive, diskette drive, four cards, motherboard with 80287 and extra RAM).
I deployed and serviced a lot of model 50Z in the late eighties and early nineties, and I have no recall of worrying about power supply load.

interalia
November 24th, 2013, 03:27 AM
Thanks for the replies folks.

Update on the PS/2 50z saga

Bought another PSU and from the same supplier a Novell NE/2 MCA NIC. I connected up the PSU without the HD module attached and it all powered up to the 'full screen insert floppy graphic'. Great I thought everything has survived the PSU blow up. Connected up the HD but nothing is happy. The light is on the PSU but the fan or HD doesn't run up and PSU seems to be under excessive load I switched it off straight away. I think there must be as short or something in the HD. So I disconnected the HD and it will then start up again to the 'insert floppy disk screen'. (If I hit a key it goes to IBM Basic. I didn't know that PS/2 still had Basic in ROM)

OK, having the HD was going to be a bonus as my ultimate intention was to get the NE/2 NIC connected to my Netware 3.12 server and run it diskless or at least floppy boot. So in went the NE/2, my reference disk (with some Novell ADF's copied onto it) and I got a 165 error. Strange I thought maybe the ADF's were wrong. I pulled the NE/2 and it booted to the 'insert disk graphic' even with the reference disk in. So I checked the diskette and tried a DOS boot disk but still the 'insert disk graphic'

I took the cover of the floppy drive and I can see that the heads move around as they should during the POST and when it looks to read from the floppy but the floppy isn't rotating. It's an ALPS drive and any suggestions as to where next would be welcome.

Thanks

Neil

interalia
November 25th, 2013, 02:45 PM
Hi

Update:

Obtained a new PSU. The hard disk must have some problem as the system will not boot (PSU light comes on but no fan or anything else). If I take the HD out it will now boot to the the full screen graphic to 'insert a floppy diskette' but now my floppy won't read and it goes to IBM Basic. (I didn't know it was still on a PS/2!).

If I take the cover off the floppy I can see that the heads move from (0-80?) in the POST but when it goes to read a diskette the disk does attempt to rotate. Any ideas?

Regards

Interalia