I have my Dad's Mac 128K that was later upgraded to a Plus. I got it working again, but recently the ground cable from the CRT yoke got too close to the red cable from the flyback, and it shorted. I'm assuming the insulation on the red flyback is not working as well as it did originally and leaked high voltage.
I still get a beep when I power it on, but no picture. I moved the logic board to my other working Mac Plus, and it booted fine, so fortunately the logic board is good. I did buy another analog board on eBay and tried swapping them, but the one I bought is in worse shape and I don't even get a beep.
I have a multimeter and logic analyzer, but I'm not sure where to start troubleshooting. Since I have a working Plus, I can compare voltages on the the two to figure out what's not working.
I do get the orange glow from the end of the CRT when it's powered on.
My logic board part number is 630-0102-N, and the eBay one is 630-0102-J, so a few revisions apart. The flyback on my board is part # 157-0042A, and the eBay one is 157-0026-B.
What component is most likely bad and how would I determine that? Assuming the flyback from my non-functioning analog board is good, I could move that and see, but I don't want to just blindly start swapping parts.
EDIT: One other thing I noticed is that the bad eBay analog board is missing one of the neon bulbs. Looks like the glass cracked, but the leads are still there. Is a missing neon bulb enough to make the board non-functional, and should I try replacing that to see if it resurrects that board?
I still get a beep when I power it on, but no picture. I moved the logic board to my other working Mac Plus, and it booted fine, so fortunately the logic board is good. I did buy another analog board on eBay and tried swapping them, but the one I bought is in worse shape and I don't even get a beep.
I have a multimeter and logic analyzer, but I'm not sure where to start troubleshooting. Since I have a working Plus, I can compare voltages on the the two to figure out what's not working.
I do get the orange glow from the end of the CRT when it's powered on.
My logic board part number is 630-0102-N, and the eBay one is 630-0102-J, so a few revisions apart. The flyback on my board is part # 157-0042A, and the eBay one is 157-0026-B.
What component is most likely bad and how would I determine that? Assuming the flyback from my non-functioning analog board is good, I could move that and see, but I don't want to just blindly start swapping parts.
EDIT: One other thing I noticed is that the bad eBay analog board is missing one of the neon bulbs. Looks like the glass cracked, but the leads are still there. Is a missing neon bulb enough to make the board non-functional, and should I try replacing that to see if it resurrects that board?
Last edited:
