===== Soft-power troubleshooting and repair =====

The following information is kind contribution by our forum members **Lydux** and **Caius** and this fix was applied to X68000 SUPER and Expert HD.

**The symptoms:** X68000 powers on fine, but does not shut down when the soft-power button is pressed. The screen fades, Power LED does not change from Green to Red and the PSU fan keeps spinning. The same happens with a regular ATX PSU.

If this is your case then the problem is almost surely located on the IO board.

Here is the power on/off logic behind the /PSON signal (named CH2 in the schematics). Click on them to enlarge.

{{:x68000:soft-power_schematic.png?400|}}

**A condition using 4 signals is used to get the X68K turn on/off correctly :**
  *Via the RTC (Real Time Clock) alarm signal (/RTC_ALARM)
  *From the expansion bus (/EXPWON)
  *Via the front power switch (/PSON)
  *Via the soft-sequence signal from the system controller (/MPWOFF)

In normal operation, all these 4 signals must go to logic High (+5v) to get a system shutdown.
The problem might be due to a signal that is always stuck Low.

If you look at the Buffered IO part in the schematics, 3 of these signals are connected to the MFP GPIP port.

**They can be queried via software and are connected like this :**

|/RTC_ALARM  |GPIP0  |
|/EXPWON  |GPIP1  |
|/PSON  |GPIP2  |

**A program for testing these signals can be found here :**

[[http://nfggames.com/X68000/Misc/Diagnostics/SoftPower%20Test%20Program/x68k_pwrtest.zip|X68k Power Test]]

**Execute it more than one time. You should get :**
  *RTC_ALARM = 1 or 0, depending on the current RTC configuration.
  *EXPWON = 1
  *PSON = 0

**If RTC_ALARM always stays 0 :**
  *Bad RTC chip (RP5C15)

**If EXPWON = 0 :**
  *Check the expansion riser, or remove it.
  *Check the "Remote" plug on the back, if I remember right, it's also connected to this line.

**If PSON = 1 :**
  *Damaged resistor R54 (should act as pullup)
  *Bad power switch

**And if all is ok, it could be :**
  *Bad IC28 (74LS08) (stuck output).
  *Bad Q9 transistor (shorted).
  *Bad C64 capacitor (generating noise).
  *IC29 (74LS244) might have bad output on pin 5.
  *The power signal from the main board, which I miss infos actually. A fix to this could be soldering a 10K ohm resistor between IC28 pin 10 and 14.