68kMLA Classic Interface
This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.
| Click here to select a new forum. | |
| PowerBook Power Supply Connector (520/520c/540/540c) | |
Posted by: croissantking on 2025-03-24 17:41:17I don't believe anyone has tried running 15V for the vmain. We're all using 16V for vmain to power the laptop. Some of us are using 15V for the vbatt pin for charging the battery.I have three power supplies. One of them is dead on the Vmain side so I switched the wires over so that Vbatt now powers the laptop. It works, mostly, just as long as I don’t draw too much power. Turning up the brightness and for example maybe inserting a floppy disk at the same time causes it to power off. | |
| Posted by: mmu_man on 2025-03-24 19:19:36 Well I guess I'll design a PCB for that to add inside, since all the boards I find on aliexpress are too large. More fun. Already found a possible chip to use. | |
Posted by: jmacz on 2025-03-24 19:20:36Well I guess I'll design a PCB for that to add inside, since all the boards I find on aliexpress are too large. More fun. Already found a possible chip to use. đź‘Ť | |
| Posted by: mmu_man on 2025-03-24 19:27:27 So, someone confirmed using 15V Vmain without trouble for a year, I guess we're pretty safe there. I have three power supplies. One of them is dead on the Vmain side so I switched the wires over so that Vbatt now powers the laptop. It works, mostly, just as long as I don’t draw too much power. Turning up the brightness and for example maybe inserting a floppy disk at the same time causes it to power off. That's not a voltage problem but a current issue: with full brightness you'll draw about an amp already idle, so using anything more will try to pull more amps, but since Vbatt is capped at 1A, the voltage will drop to compensate, and it doesn't like it. That's why Vmain can provide 1.5A. | |
| Posted by: 3lectr1cPPC on 2025-03-25 15:33:25 I am also using 15V on VBATT without issue. | |
| Posted by: mmu_man on 2025-04-04 17:43:28 So, the only thing I hate more than people forcing me to published unfinished work because they are redoing what I spend nights already doing, is people wasting time doing what I already did… GitHub - mmuman/cad-mac-pb500-pwrconn: DIY Power Connector and USB-C adapter for PowerBook 500 SeriesDIY Power Connector and USB-C adapter for PowerBook 500 Series - mmuman/cad-mac-pb500-pwrconn
github.com
Oh, A voltmeter variant, because people love useless displays… (untested yet) | |
| Posted by: mmu_man on 2025-04-05 11:45:14 Needs some more margins but it works:  | |
| Posted by: mmu_man on 2025-04-06 13:47:55 Updated the model to make it easier to assemble with the meter. | |
| Posted by: mmu_man on 2025-04-15 12:29:11 Just tested myself for the sake of it, it happily triggers overcurrent protection at 1.3A if I let it charge on a bench supply. So definitely needs some circuit to calm it down. | |
| Posted by: mmu_man on 2025-04-26 17:34:04 So, just confirmed on my PB520c, Vbatt is drawn almost directly to charge the battery (it drops at 11.7V), but it's disconnected when it thinks it's fully charged, so I only have to implement current limiting. | |
| < 2 |