ImmortanJoe
Member
Fairly recently I bought a couple of PPC macs in my far-too-long quest to have a working Old World PPC Mac again. One of which was a 5200CD. I got it working mostly, except for sound. And the HDD was very tired. Then it stopped working. Powers on. No power light. No boot chime or other signs of life. CPU gets warm.
So far in no particular order I've had it apart many times. Cleaned everything on the logic board and some cards including with demineralised water. Did a temporary re-cap with through hole electrolytics (the originals seemed fine. No shorts or anything but I was running out of ideas), checked PSU +5 and +12 voltages (perfect), Went over the logic board with a USB microscope (found some tiny flake debris from the plating on the rear backplate in less than desirable places) and tried another CUDA battery which was admittedly a crude stand in using three button cells.
Almost nothing had an effect. Except the CUDA battery. Two things. It discharges way too quickly. When it's installed the computer won't turn on. Not a bump. Not even a twitch from the 5 or 12v on the HDD connector. However if I take the battery out, wait a minute or so with the power switch off then try again it'll do the dead powerup. If the time period is shorter the PSU will bump momentarily then shut back off.
Last night i tried something a little different. I used a buck converter set to 4.5v to supply power to the CUDA battery connector. No voltage sag so I know it was getting the right voltage to the board. Same results in the computer as with the battery. But having a steady input supply let me have a better look while it was on the desk because the inability to power up with a voltage from the battery is strange.
I don't suppose anybody has a schematic of how the board handles the battery vs PSU power for the Egret? Something's weird and I'm not convinced it's the Egret chip because I can still power it up via the keyboard. If the chip was nonfunctional that wouldn't work, would it? Anyway on pin 13 I'm seeing 3.6v which doesn't seem right to me. And while I press the CUDA button it goes back up to 4.5v. Really weird. I'm also not sure what surrounding components should be seeing voltage when on battery power but it feels like I'm seeing too many. I'd really like some suggestions here.
I'll be re-capping again with SMD caps later. Because of postage cost being so high I'm holding off until I work out what components I may need for this and the other dead Mac I got on the same day (7300/200 which is also a no-start).
All of this is just a part of my quest to replace my terminally battery bombed G3 Beige. It's done though. I got it working for a while but the damage was too extensive. This is as far as I've made it in about two years.
So any suggestions, schematics, anything. Please let me know. Please.
So far in no particular order I've had it apart many times. Cleaned everything on the logic board and some cards including with demineralised water. Did a temporary re-cap with through hole electrolytics (the originals seemed fine. No shorts or anything but I was running out of ideas), checked PSU +5 and +12 voltages (perfect), Went over the logic board with a USB microscope (found some tiny flake debris from the plating on the rear backplate in less than desirable places) and tried another CUDA battery which was admittedly a crude stand in using three button cells.
Almost nothing had an effect. Except the CUDA battery. Two things. It discharges way too quickly. When it's installed the computer won't turn on. Not a bump. Not even a twitch from the 5 or 12v on the HDD connector. However if I take the battery out, wait a minute or so with the power switch off then try again it'll do the dead powerup. If the time period is shorter the PSU will bump momentarily then shut back off.
Last night i tried something a little different. I used a buck converter set to 4.5v to supply power to the CUDA battery connector. No voltage sag so I know it was getting the right voltage to the board. Same results in the computer as with the battery. But having a steady input supply let me have a better look while it was on the desk because the inability to power up with a voltage from the battery is strange.
I don't suppose anybody has a schematic of how the board handles the battery vs PSU power for the Egret? Something's weird and I'm not convinced it's the Egret chip because I can still power it up via the keyboard. If the chip was nonfunctional that wouldn't work, would it? Anyway on pin 13 I'm seeing 3.6v which doesn't seem right to me. And while I press the CUDA button it goes back up to 4.5v. Really weird. I'm also not sure what surrounding components should be seeing voltage when on battery power but it feels like I'm seeing too many. I'd really like some suggestions here.
I'll be re-capping again with SMD caps later. Because of postage cost being so high I'm holding off until I work out what components I may need for this and the other dead Mac I got on the same day (7300/200 which is also a no-start).
All of this is just a part of my quest to replace my terminally battery bombed G3 Beige. It's done though. I got it working for a while but the damage was too extensive. This is as far as I've made it in about two years.
So any suggestions, schematics, anything. Please let me know. Please.