• Please review our updated Terms and Rules here

Attemping to fix an IBM PS/2 Model 50Z

A

Allen

Guest
Joined
Jan 1, 2008
Messages
101
I have an IBM PS/2 Model 50Z (type 8550) with data I would like to retrieve. Unfortunately, the power supply appears to be dead. Since it would seem difficult to get another compatible power source, is there anyway I can revive the power supply or interface the hard drive to a modern PC?

The system seems to be in good shape otherwise, including many of the original documents. I just want to get rid of the system, but it would be nice if I can get to some of the data. Any suggestions are welcome.
 
Allen said:
I have an IBM PS/2 Model 50Z (type 8550) with data I would like to retrieve. Unfortunately, the power supply appears to be dead. Since it would seem difficult to get another compatible power source, is there anyway I can revive the power supply or interface the hard drive to a modern PC?

The system seems to be in good shape otherwise, including many of the original documents. I just want to get rid of the system, but it would be nice if I can get to some of the data. Any suggestions are welcome.
Click to expand...

The 50Z had a "DBA ESDI" HDD, proprietary to a selection of PS/2 models:

50Z
N51SX, N51SLC (a smaller size, so not an easy swap)
53SLC2 (it can be made to work)
55SX
CL57SX (smaller size again)
70
P70
8590 (It can be made to read, not to boot from; the 9590 removed the planar DBA ESDI connections)
ThinkPad 720 (smaller drive)

Unless you have another one of the models (and the normal design for DBA ESDI has only a single HDD interface) the other step might be to get another Model 50 or Model 70 PSU (I have seen them appear on eBay).
 
Power supply might not be the only problem

Power supply might not be the only problem

I appreciate the information about similar PS/2s. The power supply was working recently, but the system had problems booting because of error codes 161 and 163 (battery failure and time/date not set). Even after I installed a new battery, I would get the same error codes above. What would continue to cause these error codes, even with a newly installed battery?

If I replace the power supply, I may get the same errors. I was about to give up and strip the unit and give the parts away on this forum, unless I can figure out what to do next.
 
When the battery dies it loses its setup information. You need to use its Setup Disk do restore the information it needs in the CMOS. There are members here that can link you to the disk image so you can make a floppy and get back in business. This is a pretty common thing with errors 161 and 163, just needs the setup disk is all.

-Vlad
 
Tried using the reference diskette

Tried using the reference diskette

Actually I tried using the reference diskette, the original and backup. Still received those error codes. Does a bad power supply cause problems with the BIOS or CMOS?
 
Could the replacement battery (6V) been low, or perhaps not properly connected. Do you have the means to measure the battery voltage?
 
Allen said:
Does a bad power supply cause problems with the BIOS or CMOS?
Click to expand...
Not normally, but I have seen it in a few situations where a motherboard in an XT was replaced by a clone AT motherboard (and keyboard). The machine suffered from an inability to hold the CMOS setup for more than a few days (on each days, machine turned on in morning then off in afternoon). The problem didn't go away until the power supply was replaced by a modern one (as used in AT machines).

That problem could have been that the old XT power supply was underrated for the job, but there was talk at the time that AT power supplies were different to XT ones. Sure the AT power supply uses a pin that is unused in the XT power supply (pin 2 - extra +5V line), but there was talk at the time that other things may be happening such as delayed activation of the 'power good' line.

Anyway, that's an example of a situation where the power supply affected the CMOS setup. So maybe you can't rule out a faulty power supply as a cause.
 
Battery was tested

Battery was tested

I appreciate the explanation about the possible power supply issue. In regards to the battery, I tested it with a multimeter and it showed +6 V. I didn't see any physical damage to the red and black wires connecting the battery compartment to the system board. It's possible the system board is bad somehow.
 
I recall there being a wire jumper block on some of the 50s, I think around where the battery attached in circuit, that you had to reverse to clear the CMOS when you replaced the battery, then you re-reversed it for normal operation.
 
Druid6900 said:
I recall there being a wire jumper block on some of the 50s, I think around where the battery attached in circuit, that you had to reverse to clear the CMOS when you replaced the battery, then you re-reversed it for normal operation.
Click to expand...
What you're taking about is covered on pages 376/377 of the document I pointed to. That section is about removing a power-on password, however sentences there such as, "Make sure you either backup, or make note of the current configuration before you erase the password.", suggests that the entire CMOS data is being cleared, not just the password. Worth a try.
 
modem7 said:
What you're taking about is covered on pages 376/377 of the document I pointed to. That section is about removing a power-on password, however sentences there such as, "Make sure you either backup, or make note of the current configuration before you erase the password.", suggests that the entire CMOS data is being cleared, not just the password. Worth a try.
Click to expand...

I know that the trick works on a 55SX, but don't remember with the 50Z (no for the regular 8550 non-Z: it had a slot connector on the system planar for the speaker and battery module). Dunno why the 161 & 163 errors remain if you let it go all the way through configuring the system and setting the time. You have to do that to get past those errors.
 
What I've done so far

What I've done so far

I received this IBM PS/2 Model 50Z from the original (previous) owner who could not boot the system because of the 161 and 163 error codes. He replaced the 6-volt battery and tried many boot diskettes, including the original reference disk, backup reference disk, and various DOS boot disks. Even with a new 6-volt battery installed, the system would still display error codes 161 and 163. Because it was hung-up on these errors, the system would not boot, whether from the floppy or hard disk. The original owner was only able to get the system to display IBM basic.

He gave up, and let me have the system. I tried everything he did, and using my multimeter I verified that the system board was receiving 6 volts from the battery (I checked the red and black wires and the connections from the battery compartment to the plug on the system board). Still, I cannot get past those error codes, and pressing F1 on the keyboard only brings me to IBM basic. Therefore I cannot verify if the floppy drive or hard drive are functional.

Now the power supply appears to be dead. When plugged in and turned to the on position, the power supply does nothing, except that the yellow light yields one quick blink, but neither the yellow nor green light stays illuminated.

Because the power supply is dead, I cannot post pictures of the screen, but if you go to
http://www.neowin.net/forum/index.php?showtopic=624470 you can see a similar problem (if someone is registered on neowin.net, tell the original poster to replace the battery). This appears to be the most common issue with IBM PS/2s taken out of storage.

To respond to previous replies, I see no jumpers in or around the battery compartment, therefore I see no way to clear or reset the CMOS. In addition, I cannot access the PS/2 hardware maintenance manual (referenced site not functioning).
 
I cannot access the PS/2 hardware maintenance manual (referenced site not functioning).
Click to expand...
A copy of the manual is now at: http://members.dodo.com.au/~slappanel555/misc/ps2_hardware_maint_oct94.pdf

To respond to previous replies, I see no jumpers in or around the battery compartment, therefore I see no way to clear or reset the CMOS.
Click to expand...
Page 377 of the manual explains the situation - some of the mode 50's have no jumper and an alternate method needs to be used.

Now the power supply appears to be dead. When plugged in and turned to the on position, the power supply does nothing, except that the yellow light yields one quick blink, but neither the yellow nor green light stays illuminated.
Click to expand...
From memory, one of those lights is the power supply light and the other is the hard drive access light (it was about '92 the last time I worked on a model 50Z).
The power supply was dead in your original post, then came good, and is now dead again. I bet that it will come good again, but only for a while. You might find that it is related to temperature. I've seen that a few times (in various bits of equipment) and in all cases was caused by a capacitor in the power supply (one whose ESR I suspect deteriated to the point where the ESR was borderline for the power supply to start up).
Even if the power supply now never fires up, there is a good chance that replacing the low value electrolytic capacitors in it will get it going again. But, maybe the power supply is shutting down because of a faulty component on the motherboard.

Still, I cannot get past those error codes, and pressing F1 on the keyboard only brings me to IBM basic. Therefore I cannot verify if the floppy drive or hard drive are functional.
Click to expand...
Okay. Your earlier, "Actually I tried using the reference diskette, the original and backup. Still received those error codes" suggested to me (and probably others) that you were able to boot from the reference disk and therefore go through the setup process.

So your course of action would be:
1. Get power supply going, then
2. Determine/rectify why the machine isn't booting from the diskette drive (power supply might be cause of that), then
3. Boot from Reference Diskette and go through setup process.
 
Last edited:
Clarification

Clarification

I should clarify two points:

modem7 said "The power supply was dead in your original post, then came good, and is now dead again." Actually it was functioning fine, then it became dead. My last post should have been my original post. I was just giving more details in my last post. The original owner didn't have any problems with the power supply; I did not have any problems for the first few days, until the system shut down (powered off) by itself. Now I cannot turn on the system. Clearly, the power supply is dead.

In regards to using the reference disk or any boot disk, I inserted the disks, but nothing happened as a result. No setup screen--nothing. The only two screens I ever came across were the ones showing the error codes and IBM basic (like the pictures in the link I provided).

I'm concerned if I replace the power supply, I will still get the same error codes, unless a bad or failing power supply has something to do with those error codes (in addition to a bad 6-volt battery).
 
I'm concerned if I replace the power supply, I will still get the same error codes, unless a bad or failing power supply has something to do with those error codes (in addition to a bad 6-volt battery).
Click to expand...
Yes, no guarantees. You could have two faulty components now - power supply and motherboard.
 
Allen said:
...In regards to using the reference disk or any boot disk, I inserted the disks, but nothing happened as a result. No setup screen--nothing. The only two screens I ever came across were the ones showing the error codes and IBM basic (like the pictures in the link I provided)...
Click to expand...

You may have to press F1 for older PS/2s. It didn't run the configuration, so it didn't clear the errors. Hard to tell if it is anything other than the PSU at this point.
 
Disconnected power supply from system board

Disconnected power supply from system board

I disconnected the power supply from the system board, plugged it in, and to my surprise the power supply powered on with both the green and yellow lights illuminating. Previously, I could not get the power supply to come on when connected to the system board (see my previous two posts).

Page 141 of the referenced PS/2 maintenance manual (PDF page 155) shows the power supply voltage check for Models 50 and 70 (also attached here as Manual.jpg). Using my multimeter, I tested the power supply and got these results:

Pin 2, Pin 1: -11.35
Pin 2, Pin 3: +11.44
Pin 2, Pin 15: +5.35

The second and third results are not within the range specified by the manual. I'm confused about the values in the manual and the values on the power supply label (attached as Label.jpg)--they appear to be different. Do I have a bad power supply?
 

Attachments

  • Manual.jpg
    Manual.jpg
    24.8 KB · Views: 1
  • Label.jpg
    Label.jpg
    44.4 KB · Views: 1
Interesting to see a switch-mode power supply that doesn't need a load to start up.

Based on the power supply label, it looks like someone goofed when creating the manual.
Pin 3 is now obviously -12V in which case the minimum value is probably +9V based on the +12V specs (although 9V in my opinion is too low for a 12V line).
Pin 15 is now obviously +5V in which case the minimum value is probably going to be about the +4.5V mark.

The figures you measure look good. The manual doesn't tell us whether to make the measurements with the power supply connected or disconnected. Normally power supply measurements are made with the power supply connected.

Does the power supply stop working again when you plug it into the chassis?

If so, does the power supply then power up with the hard drive removed, or the diskette drive removed?
 
You must log in or register to reply here.
Back
Top