exxos's Atari, Amiga & retro forum

PhilC wrote: 23 Mar 2024 19:38 Well done @stephen_usher , those are definitely an interesting computer to add to your collection.

Well, I won't be keeping them. I'll be passing them on to other enthusiasts at the Portable Computing festival in Cambridge in May. I've just not got the space.

Speaking of which I've just had a message from a friend who's clearing her Mum's house and wondered if I'd like the Dragon 32 she's found in the loft, otherwise it would be scrapped.

Oh, and it seems that the foam+foil key pads have just been shipped from TexElec. I wonder how many weeks it'll take to get here.

stephen_usher wrote: 23 Mar 2024 20:04 Oh, and it seems that the foam+foil key pads have just been shipped from TexElec. I wonder how many weeks it'll take to get here.

The last items I had shipped from the US took around 3 weeks maybe 4, now you're going to be in parcel purgatory instead of me.

stephen_usher wrote: 23 Mar 2024 19:53

PhilC wrote: 23 Mar 2024 19:38 Well done @stephen_usher , those are definitely an interesting computer to add to your collection.

Well, I won't be keeping them. I'll be passing them on to other enthusiasts at the Portable Computing festival in Cambridge in May. I've just not got the space.

Speaking of which I've just had a message from a friend who's clearing her Mum's house and wondered if I'd like the Dragon 32 she's found in the loft, otherwise it would be scrapped.

So are you going to take the Dragon?

rubber_jonnie wrote: 23 Mar 2024 21:03

stephen_usher wrote: 23 Mar 2024 19:53

Well, I won't be keeping them. I'll be passing them on to other enthusiasts at the Portable Computing festival in Cambridge in May. I've just not got the space.

Speaking of which I've just had a message from a friend who's clearing her Mum's house and wondered if I'd like the Dragon 32 she's found in the loft, otherwise it would be scrapped.

So are you going to take the Dragon?

I was going to say if not - then I'd re-home it.... ;)

rubber_jonnie wrote: 23 Mar 2024 21:03 So are you going to take the Dragon?

Of course, otherwise it'd be skipped.

stephen_usher wrote: 23 Mar 2024 22:54

rubber_jonnie wrote: 23 Mar 2024 21:03 So are you going to take the Dragon?

Of course, otherwise it'd be skipped.

Splendid

stephen_usher wrote: 23 Mar 2024 22:54

rubber_jonnie wrote: 23 Mar 2024 21:03 So are you going to take the Dragon?

Of course, otherwise it'd be skipped.

That's the philosophy id use too and then re-home it at some point.

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.

Right! I'm going to make a charger unit.

I've found a buck step-down regulator which has variable voltage and as importantly, a current limiter, and I can put that with an ammeter unit and a switch and diode and put it all in a box and then power it with either a 9V or 12V unregulated supply. That should keep the Portable safe.