Thanks for your answer,
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If i unplug the bus cable i still get both LEDs.
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The processor clock is also running, i've checked it yesterday. 10MHz signal is present, it gets divided into two 5MHz out of phase signals which are also there.
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There's only ONE weird thing i've found when doing tests.
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Manual says "UMC Pin (A15U13 pin 25) should be high when INSTR PRESET button is pressed"
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The thing is that i've got the exact opposite. The "idle" state is HIGH instead of being low and when i push on INSTR PRESET, it oscillates back and forth from high to low and then stops and goes back HIGH instead of low.
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I can't really know for sure if it's supposed to do that, maybe someone here has an hp8568a and could try probing the UMC pin? That would help me a lot
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Other than that, everything else i've tested seems fine. I also checked every single wire inside the bus cable, all good.
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Checked all voltages for ripple (in case of a dead capacitor) , all good too.
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