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Repair of PS/2 Model 8580 Power Supply (by Al Savage)
Power Supply Variants
Removing Power Supply
Planar Power Supply Connector Pinout
Primary Power Supply Voltages
Power Switch Failure Rate
Power Supply Crackling Noise
Power Supply Variants
Three variants were spotted:
- 225 W, FRU 15F6548, 12 V / 7 A, 5 V / 27.75 A, -12 V / 0.39 A, red switch
- 242 W
- 250 W, FRU 57F1600
Removing Power Supply
Power off and unplug the system!
Remove rear drive carrier from DASD support structure. Unplug any four pin
drive power cables. Unplug the planar power plug. Remove the three screws that
hold the PSU in. Pull PSU out.
Planar Power Supply Connector Pinout
| |
Pin(s) |
Description |
Notes |
| |
1,4,7,10,13 |
+5 V DC |
Top row - all, bottom row - pin 10. |
| |
2,5,6,8,11,14 |
GND |
Middle row - all, bottom row - pins 13, 9. |
| |
3 |
+12 V DC |
|
| |
9 |
-12 V DC |
|
| |
12 |
Power Good |
+5 V if all voltages are stabilized |
| |
15 |
Hard-Drive LED |
Active when high |
Primary Power Supply Voltages
| -Lead Pin |
+Lead Pin |
Rail |
Vdc Min. |
Vdc Max. |
| 2 | 9 | -12 V DC | -9.0 | -15.0 |
| 2 | 3 | +12 V DC | +9.0 | +15.0 |
| 2 | 1 | +5 V DC | +3.7 | + 6.2 |
| B | D | +5 V DC | +3.7 * | + 6.2 * |
| C | A | +12 V DC | +9.0 * | +15.0 * |
* Disconnect the 15-pin connector from the system board before taking this
reading.
If the voltages are not correct, or if the fan is not running, replace
the power supply.
Power Switch Failure Rate
Peter says:
Half of the Model 80 PSUs failed with a
broken power switches. The red ones more often than the
white ones. The same switch has been used in IBM 327x
Terminals (and 525x ones) and is known for high failure
rates. It was available as spare part.
Power Supply Crackling Noise
Edward Avis says:
One thing worries me about my 8580's power
supply - it crackles. When the machine is switched _off_
there is a quiet crackling sound from the back of
the power supply, it sounds like it could be in tune with
the 50Hz mains frequency. When I first heard it I
nearly took the machine back for a refund, but it doesn't seem
to have any effect.
Peter:
Are you sure the noise comes from the rear
? The "switch cover" in the front acts like a "echo
chamber" and reflects the crackling from the switch to
the rear. On the other hand: it might be an isolation
failure on the AC Line filter as well. Or on one of the
capacitors of that filter. Had that too. You will have
to open the PSU for a failure diagnosis ... and you
should *know* what you are doing in this case. It is
dangerous to fiddle with the innards of switched power
supplies.
Something I forgot: One of my 95s made
"crackling noises" too. The clue: replace the power
cord. The one I used seemed to have too loose contacts.
After I used a different one the crackling went away.
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