exxos's Atari, Amiga & retro forum

stephen_usher wrote: 24 Mar 2024 13:31 Seeing that it's now less than 2 months until the portables exhibition in Cambridge it's time to get started testing the exhibits.

So, with that in mind I've got the Macintosh Portable on the bench and hooked it up to the bench power supply with 7.5 volts and a current limit of 1.5 amps.

Well, the Mac Portable's power management is iffy at the best of times. Without a good lead-acid battery in the bay the system can go haywire and send high voltage across the board. If you add in the flakiness of the "hybrid" "chip" which controls the voltages and you have potential disaster. Oh, and half the large chips on the motherboard aren't controlled by the power circuitry at all and are permanently powered. Never, ever try to run the machine without a working battery installed as that will damage the power circut.

Anyway, after installing the battery and using the reset and debug switch together to reset to power system I turned on the power supply. Just over 1 amp. Phew!

Powering on the machine the current went up to 1.2 amps.

As the battery charged the current decreased. Last night, after about three hours I put the machine to bed, powering off the PSU and removing the battery.

This morning I decided to continue charging the battery. After putting the battery in, resetting and powering on the PSU... 0.008 amps. Boot the machine... 0.008A... Battery starts running down. Shut down... 0.008A... Press the reset & debug buttons and whilst they're pressed, over an amp but back down to 0.008A. Went away and came back... up to 0.5A. As I said, the power management on this machine is rubbish.

Anyway, the lowest current after the battery, I assume, is fully charged is about 0.25A which doubles when the machine is booted.

Switch off the PSU and let the machine run on battery for ~5 mins and the battery decreases by about one bar. Switch on again and the PSU goes into current limit mode for about 5 seconds before the current drops down again. I can see why Apple limited the current on the original power supply. It took a couple of minutes to get below 1A (this is with the machine shut down). Getting back to full charge again took a good half an hour.

rubber_jonnie wrote: 24 Mar 2024 19:25 Wow, that seems like an awfully poor power management system, you've got a lot of trouble on your hands there!!!

stephen_usher wrote: 26 Mar 2024 10:56 Looks like both the TexElec foil+foam pads and the adjustable buck converter will be arriving next week.

However, I'll be down in Cornwall next week to deal with work on my Dad's house.

stephen_usher wrote: 27 Mar 2024 09:53 Well, I couldn't get any contractors to turn up next week, they all seem to be going on holiday, so I've cancelled my trip and my leave. There's no point taking time off if I need to use it later in the year.

Still, it means that I'll be around for the deliveries.

stephen_usher wrote: 28 Mar 2024 08:29 Looks like the pads are at the local Royal Mail delivery office.