I just purchased an Amstrad with color display, reasonably good condition for what i paid. Owner said it was left in the attic since its was last used many many years ago.
It powers up with no boot and a grey flickering (~25hz, might be its normal refresh rate) screen. Was no sync or any other signal on the display connector. All the pins were floating around 1.5v / 2v.
So went poking around with a scope while looking at the schematic.
Went through and checked a few signals on the Z80, 5V OK Reset OK.
But the clock was not present and pin is high.
After wondering where all the ICs in the schematic are, i realized i had an older revision schematic.
Found the right schematic and traced the clock from the clock generator circuitry and into the dreaded Gate Array.
Found that the 40010 IC was floating almost all of its outputs at around 1.5V.
I checked the required input on the 40010 (VCC, Reset) they looked OK.
Found that the only output that had any meaningful behavior was the READY pin, which just goes high after the power up reset procedure.
So i'm reasonably sure that i'm going to buy another 40010
My hunt for one of those begins...