Re: Lisa 2/10 power supply keeps blowing fuses, help?

Thank you everyone for the tips and suggestions!

With a lot of help from James and from a few local friends, I've determined that one of the two big capacitors is definitely bad. I've ordered a whole slew of replacements from digikey, for those two as well as for the rest of the main caps -- will post here with the repair results! I also plan to write up the steps and part numbers, and take photos of the process, for other not-very-technical collectors.

FYI to Ray, like Jason indicated, it blew the fuse even with the PSU completely removed from the computer -- so your idea about reducing the load has already been tried. I'm glad I don't have a leaking battery to worry about, though.

Incidentally, I've learned that I have to regularly hand-spin the widget drives to start them, in all three Lisas these days, like with an old prop plane; I find this equal parts depressing/cool. My pinky just fits in the gap, with the front panel off...

Thanks again, you're all terrific.

• MB

On Apr 9, 4:35 pm, "Jason Perkins" <perkins.ja..._at_email.domain.hidden> wrote:
> Seeing as it blows fuses when it's not connected to anything, I think the
> fault lies inside the PSU itself.
>
> -Jason
>
> On 4/9/07, Ray Arachelian <r..._at_email.domain.hidden> wrote:
>
>
>
> > I would try to disconnect the widget drive power and data, disconnect
> > the floppy data cables, remove the memory and CPU boards, leaving just
> > the I/O board.
>
> > Since it's a 2/10 you don't have the leaky NiCad battery problem, so
> > that's a good thing.
>
> > It probably isn't a capacitor issue, but I'd look very carefully at each
> > capacitor to see if it looks bulged out or somehow off.
>
> > It may be one of the bridge diodes, but if it's blowing the fuse, it's
> > likely a load issue, and that's why you'd want to unplug the
> > widget/floppy/cpu and I/O board.
>
> > nulldev1ce wrote:
> > > My Lisa 2/10 blinked off unexpectedly the other day, and upon pulling
> > > and disassembling the 1.8A power supply, I found that the 3A 250V buss
> > > fuse was blown. I replaced it with one of the same spec (as far as I
> > > know; does it need a slow-blow?) and put everything back together...it
> > > blew again immediately as soon as I plugged in the power cable. So I
> > > replaced the fuse again, and this time, with the PSU still outside of
> > > the Lisa, I plugged in power and it blew again. I tried one more, same
> > > thing, then stopped serial-killing fuses...

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. Received on 2015-07-15 16:37:16