I have a poorly Master 512, similar in some ways to this thread:
viewtopic.php?t=24825
On power-on, it gives the banner I'd expect for corrupted CMOS.
There's a constant lower-volume background tone all the time the machine's on - the usual boop-bip can be heard over this.
Huge chunks of keyboard don't work. From the keyboard circuit diagram, I've traced these back to:
PL1 - 3 8 13 15
PL2 - 2 3
Which seem to correspond to R0, C3, C5, C6, C7, and C9 going into IC 16 (I hope it's not the custom chip).
The keyboard works fine in a different Master, and the keyboard from a working Master exhibits the same faults.
There's continuity between the relevant pins on PL11/24 and IC16.
Any suggestions on where to test next, before I break out the desoldering station and do somethng I might regret?
Edit: Since I don't have a working 'R' key, I can't reset the CMOS
viewtopic.php?t=24825
On power-on, it gives the banner I'd expect for corrupted CMOS.
There's a constant lower-volume background tone all the time the machine's on - the usual boop-bip can be heard over this.
Huge chunks of keyboard don't work. From the keyboard circuit diagram, I've traced these back to:
PL1 - 3 8 13 15
PL2 - 2 3
Which seem to correspond to R0, C3, C5, C6, C7, and C9 going into IC 16 (I hope it's not the custom chip).
The keyboard works fine in a different Master, and the keyboard from a working Master exhibits the same faults.
There's continuity between the relevant pins on PL11/24 and IC16.
Any suggestions on where to test next, before I break out the desoldering station and do somethng I might regret?
Edit: Since I don't have a working 'R' key, I can't reset the CMOS
Statistics: Posted by Boydie — Sun Nov 24, 2024 11:54 am