Notes on repairing the Apple Lisa power supply

From: Joe <rigdonj_at_intellistar.net>
Date: Thu May 25 17:46:57 2000

At 04:34 PM 5/25/00 -0400, R. D. Davis wrote:
>On Thu, 25 May 2000, Joe wrote:
>> I have a Lisa 2/5 that doesn't want to work. Here's some things that I've
>> found out in the process of troubleshooting it.
>
>Weierd, I could have sworn I just read the words "process of
>troubleshooting" above; I'd better get my eyes checked.


   Weierd? Maybe the problem isn't your eyes.
>
>> (2) The card cage must be installed in a before the PS will turn on but
>> the memory and I/O cards need not be installed.
>
>Did you test the power supply with a dUmmy load first, using a
>voltmeter as well as an oscilloscope to check for voltage levels, as
>well as spikes, before applying power to the boards, and applying any
>necessary test connections to the PSU's input connectors?

    No, I didn't since I took it out of a working machine. I don't mean WAS
working, I mean one that I have been using and that I tested less than five
minutes before pulling the PS.

>
>> (5) An I/O card from a 2/10 will work in a 2/5, at least properly enough
>> to power it on and get a display.
>
>"properly enough"?

    The 2/10 doesn't have an external parallel port and there are other
differences but you can still get a display with it. That's what I'm
talking about. FYI the parallel port in the 2/10 is used for the hard
drive. I did disconnect the drives before starting.

>
>> >(6) A "bad" I/O card in a 2/5 will prevent the PS from turning on and will
>> cause the PS to appear defective.< (see note 2!)
>
>Don't you mean an I/O card with a short circuit somewhere?

   Did I say short circuit? Hmmm, nope I don't see that anywhere.


 If you
>don't know what a short circuit is, just ask, or experiment... e.g.,

   Thanks but I've seen plenty of them.

   In case you can't figure it out, the point is that a "bad" I/O card will
make it appear that the power supply is bad. Perhaps that's one reason that
so many people have Lisas with what they think has a bad power supply.


>if, for example, you touch the conductors connected to the hot and
>ground connectors of a mains socket, and a fuse blows or a circuit
>breaker trips, you'll find that you've learned a lot about short
>circuits and saving classic computers. ;-)
>
>> My 2/5 will not power on. I installed a known good PS from a
>> 2/10 and it still doesn't work. The 2/5 PS DOES work in the 2/10 so
>> it is good. The
>
>Surely you jest...
>
>They why did you risk swapping in another un-tested, even though
>thought to be good, PSU, and risk additional damage to the boards?

  Yes, you'd better have your eyes checked! I said KNOWN good power supply.
You even quoted me above.


>Didn't you test the 2/5 PSU before doing anything else? Why put the
>2/10 at risk by putting a PSU in suspect condition into it?

    I tested BOTH power supplies as best as possible before swapping them.
They were both good. That was proven with they both worked in the other
machines. Oh, and in case you think I shouldn't have swapped the supplies
to the different machines, I did verify that they were compatible in one of
the Apple repair manuals first. Would you like for me to scan and post the
appropriate page? I have it right here is front of me. The same manual
states that the cards are also interchangeable but that there are some
differences in the I/O card due to the hard drive (I disconnected it.)

>
>Hmmm... have you considered computer preservation as a hobby instead
>of computer demolition?

   Have you considered minding your own business and not putting words in
other people's mouths?

>
>> 2/5 will power up with an I/O board from a 2/10 or with no I/O board
>> installed so the problem appears to be in the I/O board. The battery
>> condition seems to not matter. Does anyone have a schematic of the
>> interlocks and interconnects for the Lisa 2/5 or know what signals the
>> power supply gets from the I/O board?
>
>Shouldn't you have tried to find that out before swapping things
>around without knowing what you were doing?

    I knew what I was doing. Shouldn't you find out what you're talking
about before you start shooting your mouth off? I don't know what kind of
hair you have up your ass but I just e-mailed you and offered you some of
the DEC 11/44 stuff that you were looking for. Now you can forget that!

    Joe
>
>--
>R. D. Davis
>rdd_at_perqlogic.com
>http://www.perqlogic.com/rdd
>410-744-4900
>
>
Received on Thu May 25 2000 - 17:46:57 BST

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