First off, are there any step-by-step guides to troubleshooting a IIGS logic board in a somewhat dead state?
I have a logic board, ROM01, part number is 607-0713D.
With no cards installed and no keyboard connected, I power it on and it displays the checkerboard pattern, with white and black boxes. There is also no beep out of the speaker.
I have a multimeter, logic probe, and oscilloscope. I have some knowledge of 8-bit CPU troubleshooting, but I'm very unfamiliar with the IIGS logic board.
Voltages are all there. No short-to-ground on anything detected.
Probing the 65816 CPU, I do detect a RESET signal on pin 40. With the probe on pin 40, I turn the logic board on, and for a short time it blinks LO, and then it switches to HI and it stays there. There's also clock on pin 37 - I didn't measure the frequency of this signal, but I presume it is getting a clock signal.
I also probed address lines A12 thru A15, with A12 fluttering extremely fast, while A15 flutters the slowest of these address pins. I also probed all the data lines D0 thru D7, and they all appear to have digital signals running through them. So it appears that I have a good CPU, the CPU is resetting fine on power-up, it is trying to access address lines, and it appears that there is data going across the data lines.
At this point, does it appear to be bad RAM? There are different sets of RAM on this logic board - standard RAM and fast RAM. And, because of the current state of the logic board, I can't run any diagnostics.
Thank you!
I have a logic board, ROM01, part number is 607-0713D.
With no cards installed and no keyboard connected, I power it on and it displays the checkerboard pattern, with white and black boxes. There is also no beep out of the speaker.
I have a multimeter, logic probe, and oscilloscope. I have some knowledge of 8-bit CPU troubleshooting, but I'm very unfamiliar with the IIGS logic board.
Voltages are all there. No short-to-ground on anything detected.
Probing the 65816 CPU, I do detect a RESET signal on pin 40. With the probe on pin 40, I turn the logic board on, and for a short time it blinks LO, and then it switches to HI and it stays there. There's also clock on pin 37 - I didn't measure the frequency of this signal, but I presume it is getting a clock signal.
I also probed address lines A12 thru A15, with A12 fluttering extremely fast, while A15 flutters the slowest of these address pins. I also probed all the data lines D0 thru D7, and they all appear to have digital signals running through them. So it appears that I have a good CPU, the CPU is resetting fine on power-up, it is trying to access address lines, and it appears that there is data going across the data lines.
At this point, does it appear to be bad RAM? There are different sets of RAM on this logic board - standard RAM and fast RAM. And, because of the current state of the logic board, I can't run any diagnostics.
Thank you!