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--- x68000:soft_power_switch_troubleshooting_and_repair [2012/11/20 22:40] – eidis
+++ x68000:soft_power_switch_troubleshooting_and_repair [2019/08/27 20:45] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-===== Soft power switch troubleshooting and repair =====
+===== Soft-power troubleshooting and repair =====
-The following information is kind contribution by our forum members **Lydux** and **Caius**. This fix was applied to X68000 ExpertHD and SUPER.
+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 symptom: System powers on fine, but does not go into stand-by when the soft-power button is pressed. The screen fades, Power LED does not change from Green to Red and the system fan keeps spinning. The same happens while trying to use a regular ATX PSU.
+**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.
-The problem is almost sure located on the IO board.
+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.
-Here is the power on/off logic behind the /PSON signal (named CH2 in the shematic)
-{{:x68000:soft-power_schematic.png?900|}}