Re: My sick 2/10

From: Macmoni <macmoni_at_email.domain.hidden>
Date: Thu, 25 Nov 2004 20:12:02 +0200

Hi Jason,

your search to find the error is going on.
> I have tried powering the Lisa with the drive cage removed, same result.
> I have not tried powering it on with the ram cards removed. I'll try that
> now.
Check that first, before we take a closer look to the PSU

> ... third pin from the yellow plactic piece on the first expansion slot was
> bent, and was contacting the pin acrost from it. I have a piece of paper in
> there now, insulating it.
Could be, but mustn't. But it perhaps would be a good idea to insulate the whole expansion slot by putting in some sort of plastic e.g. a master-card or sth. like that :-)))
> I had removed the motherboard from the metal base and didn't see any burnt
> traces or anything.
The Lisa PSU shuts down much faster than anything will begin to burn or melt, fortunately :-)
There is only one exception of that rule, and this is, if your CRT-Board is bad. Then you can under some circumstances smell a little burned material, cause one of the potentiometers of the Board can burn. But this is very very unlikely - and this error would NOT cause the PSU to shut down.

Perhaps you can check the PSU voltages, if removing the RAM cards does not lead to a now working Lisa.
You have some voltages easy to measure by using the power-connector cable of the drive cage.
There should be +5V, +12V availlable for a very short time, during the "whump"
If those two voltages (or one of that) isn't availlable, then you have to check the PSU - but you have to be very careful. High voltage !!! Wait a few minutes to get all Caps discharged after the last attempt to fire it up.
Then check all diodes at the left side of the PSU mounted vertically on the PSU-Board (when the connections look forward and the power plug is behind) and the double-diode (looks like a power-transistor) near the low-voltage Caps in front.
Perhaps one of those diodes has a shortcut, which leads to an overcurrent.

Then check all low-voltage Caps in front. If they're bad, then they cannot temporary store the power, and your Lisa will be feed with a frequent DC. Not very good in deed, and one more reason for overcurrent to switch the PSU off.
If you're familiar with electrical devices, you also can test the opened PSU under voltage and take some measurements to proceed a littler faster :-) But do not do that, if you are not an electician or electric engineer AND don't do that alone in case of something is happening to you. Somebody should be able to call emergency in worst case :-)))

greetings TOM from Bavaria

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Received on 2004-11-25 11:19:26

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