Re: My Lisa 2/10 won't power on anymore

This might be helpful---I was able to carry out a bench test of 1.2A and 1.8A power supplies using the procedure I describe here:

https://68kmla.org/forums/index.php?/topic/30781-apple-lisa-doesnt-boot-need-help-troubleshooting/&tab=comments#comment-335026

If you do the same, you may be able to isolate the problem to the PSU---or get closer to ruling it out. Do make sure you have resistors that are up to dissipating all that power, though!

Oh, and: if you do decide to test the PSU in this way, don't forget that you'll need to defeat the safety interlock switch on the back near the monitor adjustment controls. It's easy to forget this when the PSU is on the bench and decide that the main power supply is broken somehow :-)

--Tom

On Friday, February 16, 2018 at 5:45:34 PM UTC, James MacPhail wrote:
>
>
> I don't recall the whirring/buzzing symptom... rapid "clicking" is a
> common description for a power supply problem, I presume that doesn't
> fit in this case.
>
> You could unplug the video board and see if the symptoms change. You
> could also remove memory boards.
>
> It isn't clear if the failure to power-on appeared before or after
> the recapping project. If before, have the symptoms changed as a
> result of recapping? If after, how long did the system work before
> the problem appeared?
>
> I suggest double-checking the parts you replaced to see if any have
> failed prematurely or were put in the wrong place or backwards.
>
> The COP power is supplied by a small "always on" transformer in the
> power supply. The fact that the COP has power shows the fuse is good,
> but doesn't indicate anything about the large switching power supply
> that is activated by the power switch. It is normal that the voltage
> adjustment doesn't affect the standby power voltage.
>
> If you put your voltmeter on each of the various voltages on the I/O
> board (+/-12V and +/-5V) and push the power button briefly, you might
> (or might not) see a clue as to which voltage isn't working.
>
> Good luck!
>
> James
>
> At 10:39 PM -0800 2/14/18, Rebecca Bettencourt wrote:
> >I acquired a Lisa 2/10 a while ago that stopped powering on while I
> >was working on fixing the keyboard.
> >
> >I've recapped the (1.8A) power supply and the video board, and I've
> >tried adjusting the voltage on the power supply. No matter what the
> >voltage adjustment is set to, all I get is a whirring/buzzing noise
> >from the power supply when I press the power button.
> >
> >Pin 9 of the COP421 shows 5.34V (no matter the adjustment), and I do
> >get a signal on pin 12 of U7F when I press the power button. This is
> >all with the drive cage removed.
> >
> >I'm out of ideas for now. What other components should I try
> >replacing or things should I check?
>

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