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M0SOE_Bruce · 16th Sep 2018, 3:09 pm

It sounds like the PSU could be crowbarring as well. Best way to isolate is divide and conquer. Separate the mobo and measure the resistance of the + - 5V and + - 12V pins to ground. There shoud be some resistance. I had a Compaq mobo with the same symptoms and it was found to be a shorted bypass tantalum on the mobo.

As others have suggested it may be time for a capacitor makeover in the PSU.

16th Sep 2018, 3:09 pm	#17
M0SOE_Bruce Pentode Join Date: May 2013 Location: Deal, Kent, UK. Posts: 139	Re: IBM PS/2 seems to have got stuck! It sounds like the PSU could be crowbarring as well. Best way to isolate is divide and conquer. Separate the mobo and measure the resistance of the + - 5V and + - 12V pins to ground. There shoud be some resistance. I had a Compaq mobo with the same symptoms and it was found to be a shorted bypass tantalum on the mobo. As others have suggested it may be time for a capacitor makeover in the PSU.