+KylJoy Posted March 18, 2021 Share Posted March 18, 2021 On U5 of "black screen" unit: 1 - sometimes pulses, sometimes high, sometimes low 2 - sometimes pulses, sometimes high, sometimes low 3 - sometimes pulses, sometimes high 4 - usually pulses, sometimes low 5 - usually pulses, sometimes low 6 - high 7 - usually pulses, sometimes high, sometimes low 9 - high 10 - high 11 - high 12 - high 13 - high 14 - high 15 - high On U5 of known good unit: 1 - pulses, then goes low 2 - pulses, then goes low 3 - pulses 4 - pulses 5 - pulses 6 - high 7 - high 9 - high 10 - high 11 - high 12 - high 13 - high 14 - high 15 - pulses Thanks for the assistance! Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 18, 2021 Share Posted March 18, 2021 (edited) So the processor is hanging out in the E000 range, according to that. Did you make sure to press reset to see if you get at least an initial pulse on pin 15? Edited March 18, 2021 by ChildOfCv Quote Link to comment Share on other sites More sharing options...
+KylJoy Posted March 19, 2021 Share Posted March 19, 2021 4 hours ago, ChildOfCv said: Did you make sure to press reset to see if you get at least an initial pulse on pin 15? I can't see any initial pulse on 15 of the bad unit. FYI, this very IC seems to work fine in a known "good" unit. Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 19, 2021 Share Posted March 19, 2021 12 hours ago, KylJoy said: I can't see any initial pulse on 15 of the bad unit. FYI, this very IC seems to work fine in a known "good" unit. You mean you pulled the IC and tested it in the other unit? So the problem is the input to U5 then, not the output. Its inputs are driven entirely by the CPU. If you never see a pulse on the BIOS line at all, even after hitting reset, that means the CPU isn't doing what it's supposed to. Quote Link to comment Share on other sites More sharing options...
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