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We've made some quality of life improvements to the Trading Post. More info here.
jmacz journey
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I'm using a bench supply providing 1A and 6V so I took a chance using the only fuse I have on me, a 2A/250V one. Should be fine for now since I'm using this bench supply.
No chime through the speaker when I press a key to boot.. but I saw current draw from my bench supply after I pressed a key! Tried the headphone jack and I've got a chime!
But nothing through the speaker. It's a 30 ohm one. I've tried others and same thing so it's not the speaker. Both speaker pins seem to have proper continuity - one is ground and the other has continuity to a pin on the headphone jack. Maybe it's the usual issue with the headphone jack switch? But testing it with/without a headphone plugged in seems to the do the right thing. Gonna try taking off the headphone jack to examine it further.
Yeah seriously.
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Tried deoxit on the speaker pins first and that did the trick. The speaker's working properly now. Now gotta find a proper 7A rated fuse.
Found it... the MISC GLU's AS line is disconnected. All the other chips that are connected to AS have continuity except the MISC GLU chip. It's properly connected to the pad but even the pad doesn't have connectivity to the rest of the AS network. Not quite sure where the break is. The pin 7 pad seems to go under the MISC GLU chip and given that chip isn't near any caps, I am not going to take that one off. The other two chips that connect to AS that are near leaking caps are the VIA chip (close) and the SWIM chip (not that close). I'm guessing it broke near the VIA chip but need to take another pass with a microscope to see if I can see it. In the meantime it's bodged to the CPU.
It's getting to the question mark floppy icon. Now I'm trying to get a 6.0.8 image so I can attempt a full boot.
SCSI, SWIM, VIA, PM all checked out for continuity. Need to finish CPU, CPU GLU, and MISC GLU. The AS one is still bothering me in terms of where it broke as I don't see it.
I've pulled off the board the chips that were around leaking capacitors. Surprising how much juice is still there under the chips even after how long the board soaked in IPA. Did a pass with a microscope and don't see anything material.. for suspcious ones, I beeped them out and they were ok.
I've pulled off the board the chips that were around leaking capacitors. Surprising how much juice is still there under the chips even after how long the board soaked in IPA. Did a pass with a microscope and don't see anything material.. for suspcious ones, I beeped them out and they were ok.
I came through this issue of never seeing the question mark on a PowerBooks where the hard drive was dead but still connected. So I suggest to make sure no SCSI drive is connected. You could even disconnect the floppy drive in case it failed as well.
Yeah, it’s just the logic board. Nothing but speaker, power, screen, that’s basically it. The fix for the AS line corrected the issue, but then it happens on restart. I am wondering if the current needs to burst above 1.5 amps during a restart. I have it capped at 1.5 amps as I have a 2 amp fuse right now instead of the normal 7 amp one which is on order.
Yeah, my bench supply is showing under 1 amp but curious if it draws more during restarts or boots.
I'm going to take a look at better understanding where the break was for the AS line.. that might yield some clues.
Moving the portable discussion here: https://68kmla.org/bb/threads/portable-5126-logic-board-debugging.53205
Portable is working. Had two broken traces... one was delivering 12V to the audio circuit. The second was IPL0 to the CPU GLU chip (still not sure how that one broke).
Waiting for some silicone tubing to arrive to finish the trackball, and some silicone grease for the hinges.
I did get a battery for it. It's a Lipo. A lot of folks online say you can just charge it like a lead acid battery. But some suggest not to? I made a custom 3D printed holder for it as it's smaller than the stock battery. Nothing fancy. Just needed something to hold the copper contacts and hold the battery in place inside the compartment.
Also did @David Cook's LED backlight modification. I didn't use a secondary board for providing 12V... I just ran it from the logic board and added a connector so I can easily remove the display.
The laptop came with 2 of the stock batteries (both dead). Not sure what I'm going to do with them. Maybe when I have some time, I'll try cutting apart the case so I can reuse it and then recycle the batteries.
Waiting for some silicone tubing to arrive to finish the trackball, and some silicone grease for the hinges.
I did get a battery for it. It's a Lipo. A lot of folks online say you can just charge it like a lead acid battery. But some suggest not to? I made a custom 3D printed holder for it as it's smaller than the stock battery. Nothing fancy. Just needed something to hold the copper contacts and hold the battery in place inside the compartment.
Also did @David Cook's LED backlight modification. I didn't use a secondary board for providing 12V... I just ran it from the logic board and added a connector so I can easily remove the display.
The laptop came with 2 of the stock batteries (both dead). Not sure what I'm going to do with them. Maybe when I have some time, I'll try cutting apart the case so I can reuse it and then recycle the batteries.
Nice optimization. That frees up space and avoids coil whine. If the hard drive is replaced with a solid state drive, there should be plenty of 12v power available for the backlight.
Yup, waiting for an adapter to arrive so I can use a ZuluSCSI.
