Posted By
CzajNick
on 2016-01-09
15:08:47
|  Re: TED is dead? Strange plus/4 failure...
Not sure if it was clear enough, but I essentially tried one CPU + TED set in both Plus4s, getting exact same result. That's why I suspect CPU or TED malfunctioning.
As of IRQ, my initial thought was that CPU is stuck exactly because broken TED or CIA chip pulls it low (mind the inverted logic - low is active). So I tried to disconnect TEDs IRQ (by bending pin 8 out), and IRQ remained high (inactive) this time - that's how I know TED is responsible for signaling the interrupt. My initial idea was that CPU was stuck in the interrupt handler, but now I think it might be other way around - CPU doesn't handle interrupts at all.
I start to think that the best thing (in terms of effort) to do is to find another TED and/or CPU for replacement  Looking around for used C16 
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