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x68000:soft_power_switch_troubleshooting_and_repair [2012/11/21 00:31]
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x68000:soft_power_switch_troubleshooting_and_repair [2019/08/27 20:45]
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-===== Soft-power troubleshooting and repair ===== 
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-The following information is kind contribution by our forum members **Lydux** and **Caius** and this fix was applied to X68000 SUPER and Expert HD. 
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-**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. 
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-If this is your case then the problem is almost surely located on the IO board. 
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-Here is the power on/off logic behind the /PSON signal (named CH2 in the schematics). Click on them to enlarge. 
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-{{:​x68000:​soft-power_schematic.png?​400|}} 
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-**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) 
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-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. 
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-If you look at the Buffered IO part in the schematics, 3 of these signals are connected to the MFP GPIP port. 
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-**They can be queried via software and are connected like this :** 
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-|/​RTC_ALARM ​ |GPIP0 ​ | 
-|/​EXPWON ​ |GPIP1 ​ | 
-|/​PSON ​ |GPIP2 ​ | 
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-**A program for testing these signals can be found here :** 
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-[[http://​nfggames.com/​X68000/​Misc/​SoftPower%20Test%20Program/​x68k_pwrtest.zip|X68k Power Test]] 
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-**Execute it more than one time. You should get :** 
-  *RTC_ALARM = 1 or 0, depending on the current RTC configuration. 
-  *EXPWON = 1 
-  *PSON = 0 
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-**If RTC_ALARM always stays 0 :** 
-  *Bad RTC chip (RP5C15) 
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-**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. 
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-**If PSON = 1 :** 
-  *Damaged resistor R54 (should act as pullup) 
-  *Bad power switch 
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-**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. 
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 x68000/soft_power_switch_troubleshooting_and_repair.txt ยท Last modified: 2019/08/27 20:45 (external edit)
 
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