Adrian's Digital Basement repairs a Lisa 2/5

[stepleton]

That's amps of AC input current, and multiplied by input voltage you get power. The 220VAC-240VAC PSUs need less current for the same power since the voltage is higher.

The output current ratings for the 1.8A supply are not available anywhere that I'm aware of, but the 1.2A PSU is specified in the hardware manual (e.g. PDF page 73 of this document).

We see that actually my worries were misplaced and Adrian may not have exceeded the PSU spec at all. +5V can go up to 8A, and while Adrian IIRC pushed +12V to 3A and not the 2A listed here, the 1.8A PSU surely has capacity for more in consideration of the Widget spindle motor.

That said, I would still be a little surprised if the Lisa 1 or Lisa 2 consumes anywhere near 8A on the +5V rail. Of course Apple must have spec'd it for a reason; what am I missing?

[TorZidan]

His European 220-240v PSU is labeled 1A. I've never seen that before. Each one that I have reads 1.2 or 1.8A. I learn something new every day around here.

The actual rating on a PSU is how much power it can output. It is the same: 150w, on the European PSU and on it's US equivalent model. The "1A" vs "1.2A" is more of an informative value and is derived from e.g. 150W/120V = 1.25A (they print 1.2A), or 150W/220V = 0.7A, they print 1A.

Also, the "amps" on the output rails (5V, 12V and others) can me much larger than 1A.
The LisaHardwareManual1983.pdf , page 259 lists:
+5V +/-5% , provides 4 to 8 Amps   
+12V +/-8%, provides 0.35 to 2 Amps
+33V (acceptable values are between 32 to 36V) , provides 0.3 to 0.7 Amps
-5V +/-10%, provides 0 to 0.2 Amps
-12V +/10%, provides 0.01 to 0.2 Amps
+5v Standby +/-5%, provides 0 to 0.1 Amps

[ried]

Very informative! Thank you both. 

[sigma7]

a little surprised if the Lisa 1 or Lisa 2 consumes anywhere near 8A on the +5V rail. Of course Apple must have spec'd it for a reason; what am I missing?

I've measured the +5V current drawn by the card cage at over 6A when loaded with 2MB memory, without any expansion cards or floppy drive(s). Your milliamps may vary.

[AlexTheCat123]

Really there's a part of me that wishes that his Lisa were slightly more broken, if only because it would require him to discover and to show-and-tell more of the machine through troubleshooting!

Ha, I told him the exact same thing! But it's already been a bigger multi-part project than the stuff he normally tackles, so maybe it's for the best that it's this way...

[stepleton]

He's got that Plexus UNIX machine sat behind him that I seem to recall is a bit of a basketcase. I always wonder what's cooking with that thing. I can see it not being the best for views; maybe it's now reserved for Patreon members. (Ashamed to admit that I am not one at the moment.)

Oh well. If you want a Project, get yourself a PERQ; it worked for me! (And is probably still working for me; who knows what will break next?)