So it's official: I have the kiss of death to Acorn A4s. I received another two A4s from Meadowhead School today, bringing my A4 collection to four. Both 2MB floppy drive only machines - the lack of hard drive noises was disconcerting.

Both powered up with the LCD off - some blind typing revealed their CMOS batteries were flat and a power-on delete fixed that for the second machine. The first machine powered up fine (floppy drive seek, caps/num lock lights respond to their keypresses), but evidently my blind typing wasn't enough to awaken it. Switched the power brick to the second machine and got that working. Swapped back again by removing the brick's 9way D connector from the second machine and inserting it into the first, which was switched off. A loud crack was heard. That didn't sound good. The machine then only has the 'mains adaptor' light and not the 'battery charging' light on, and refuses to power up. I think I've fried the internal PSU system :-( Hopefully the crack means something fairly obvious has blown, and the A4 logic is OK.

So the moral of this story is... never connect the power brick when energised.

In other news it might be nice to find some suitable ZIP DRAM to expand these to 4MB. Not that it's exactly first on the priority list.

Yesterday I collected the Acorn A4 that Julia Cooke very kindly gave to me. The most pristine A4 I've ever seen - my battered example looks a poor relation next to it! This is my second A4, if you don't count the Triumph Alder 386-in-A4-case (well, actually the A4 is in the TA 386 case).

Worked very well last night... screen is very clear with no defects (it's one of the Sharp panels with better contrast than the Epson panel in my A4 and that I was selling). She also provided a parallel port Zip which worked fine and an Eesox parallel port CD-Rom that I couldn't persuade to read data CDs (even properly mastered ones).

However it seems to suffer from the power supply problems that dog many A4s. Left the A4 on charge and later in the evening it had died. Charging light was still orange (charge) and the LEDs claimed the computer was on but the screen was black and the keyboard LEDs wouldn't change - it was dead, in other words. Switch off and on again: hard drive spins up and all three keyboard LEDs come on but no floppy drive seek (which indicates that the processor and OS have booted correctly). That tells me the +5V power rail is up but for some reason the machine hasn't booted.

Tried again this morning to the same effect. The battery isn't holding enough charge to be able to run the machine for more than a second but from the LEDs it might be booting properly in that time. Another odd symptom is that when switched off and the charger is unplugged the top LED (computer on IIRC) is faintly on. I've never seen that before. After running the machine from battery that's stopped... I wonder if the battery is somehow powering the LED when the machine is off? Which seems to suggest something funny in the PSU circuit. This is different to the A4 PSU faults I've seen before.

So either I have the kiss of death to such things or this A4 hasn't come out of the cupboard very well.
I have the spare room back so I think a dissection is called for at some point.