POST Errors
   If multiple errors occur during POST, resolve them in the order that they are presented.
 
   Always cold boot and run Advanced Diagnostics (go into System Programs and at the main menu do a Ctrl-A) before replacing components when trying to resolve software problems. If diags don't fail, replacing components will probably not solve the problem. Refer to the software vendor for possible patches. The software may not be supported on the system. 

Multiple POST Error Procedure
   If more than one error code is displayed, diagnose the first error code first. The cause of the first error code could cause other devices to fail. This is especially important with configuration errors.

   If no error codes appear, see if the error symptoms are listed in the Error list.

   If an adapter consists of multiple FRUs (memory for example) remove the optional FRUs one at a time to see if symptoms change before replacing the adapter.

   External surge suppressors may be the source for hard to diagnose problems.

PS/2 Beep Codes
A o (small o) indicates a short beep
A - (underscore) means a long beep

o            Normal Operation
o o           A problem exists, check config. Run diags, if no error code displayed
_ o           Display or display adapter problem.
_ o o         Display or display adapter problem.
_ o o o       Display or display adapter problem.
o o o o o o   Continuous short beeps. Check keyboard.
________      Continuous solid beep. System board.
 

Dead System (no POST, screen blank, no beep) 
   The most likely cause is a device that is shorting out the power supply. An improperly inserted memory module, a defective adapter or device can cause a short circuit. To prevent damage to a power supply, the system board must present a "POWER GOOD" signal to the power supply in 150mS or less. If this does not occur, then the power supply shuts down internally. 

   Known dufus tricks- SIMM inserted backwards (with enough force ANYTHING is possible). adapter not fully seated in expansion slot, power cord not plugged in, unsupported/defective adapter (Non-IBM adapter, like ALR..), or with a heavily loaded system, too many drives starting at once (overcurrent as the drives attempt to spin up- leave motor start jumper open to start drives after the controller interrogates them) 

Troubleshooting a Dead System
1.   Verify power is on (IS cord plugged in?). If the system has power, then go to #2

        NOTE:  Intermittent and very difficult to diagnose system problems, may be caused by line cords which are not fully seated, or are too loose to make a tight connection.

When troubleshooting intermittent post errors, or any unusual, system problems, (for example; system performs power-on reset unexpectedly during operation) check the line cord for proper seating.  Slight forming of the male contacts in the system unit power supply connector may correct the problem -OR- you can sometimes adjust the female contacts in the line cord plug.

WARNING! Remove line cord from outlet before working on line cord contacts!

Replacing the line cord may be necessary in some cases. Both ends of the line cord should be checked.

2.    Remove all adapters, options, extra memory, etc. 
       Remove all external connections, KB, mouse, display, etc. 

3.    Plug in, power on, listen for a beep. The beep indicates POST has run.  Multiple beeps may occur. 

4A. If no beep is heard, verify continuity through speaker.
         If OK, replace system board memory and retry # 3. 
         If still no beep, verify PSU voltages. If voltages are OK, replace system board. 
         If voltages are incorrect, replace the power supply. 85/95 PS 90 PS 500 PS

4B.  If a beep occurs, reinstall adapters one at a time and return to step 3. When 
       something is added and the beep is no longer heard, the last item plugged in is 
       probably defective. At this point, it is not necessary to reconfigure the system 
       each time an adapter or device is added because we expect any beep. 

Batteries
   Defective or weak batteries can cause loss of all setup information. If only part of the setup is lost, the battery is probably NOT the cause. Inaccurate time is usually caused by software, but some of the older models with the 6v batteries are more prone to time slowing down.

That worked any time I'd landed on the "ASCII-console mode" during fiddling with SOD- / bad-DMA platforms and Kingston Turbochips :-) Moving only the jumper or only isolating the battery often did *not* cure it. Which is slightly strange.

Password Jumper:
It may be necessary to move the power-on password jumper (J16-8595 or J10 - 8590) to enable an IML to the reference diskette in drive a. Moving this jumper forces the stage 1 POST routine to branch to the diskette, rather than attempt to load stage 2 from the Fixed disk system partition. (A reference diskette must be present in the a: drive)

The Stage 2 POST code on the reference diskette is identical to the code loaded onto the system partition, Moving this jumper sets all default values, except ASCII terminal mode. It should be further noted, that moving the Power-On password jumper is effective for only 1 Power-On cycle because stage 1 POST tracks (records) the position of the jumper each time it is run.