Re: Lisa psu repair question

Hello Rudi,

well, the sentence
> Replace the electrlyt-caps in secondary voltage unit, located near
> the output pins of the psu-board; they must be bad due to their
> age... they're dry for shure.

should be exact enough, or shouldn't it? "ALL caps, located near the output pins of the psu-board"

Those caps are responsible for the adaequate smoothing of the +5V, +12V, -5V, -12V and the permanent +5V output of the psu and in order to prevent further faults you should replace them ALL. You can also solder them out and try to measure their values, sometimes you find some really bad ones, when comparing the value with the printed value on the caps.
But often enough you can't determine any bad caps by having an optical "look over it"

Concerning the temperature sensor in your psu. Perhaps it would be an option to upload a picture of the item you mean? Because there's definitely no temp.-sens in a Lisa-psu and I wonder what kind of manual you have, when there is one?!

greetings: TOM from Bavaria, the center of europe, the country with the marvellous castles of Koenig Ludwig, the alps and the original Octoberfest in Munich

Am 22.08.2011 um 10:55 schrieb Rudolf Brandstötter:

> Many thanks to the replies so far!
>
> I could fix problem #2: The #52 error had nothing to do with the
> COPS 421 chip on the I/O board; I changed the CPU board again and
> the error has gone. The CPU board works fine in another Lisa, so
> strange problem with strange solution - but it helped.
>
> The problem with the power supply still exists. I wonder why in the
> manual there is a temperature sensor mentioned but experts here say
> there isn't one.. I have now 3 power supplies that suffer from that
> problem; the capacitors look fine - optically there are no signs
> that they might be the problem. Should all capacitors be replaced
> or are there some usual supects?
>
> Another thing: I'm looking for a good working Lisa 1/2 motherboard
> (that one with the parallel port on the back). Does anyone have a
> spare board? I'd buy it or trade it against other Lisa stuff (CPU
> board, I/O board, ... whatever).
>
> Thanks
> Rudi
>
>
>
> -------- Original-Nachricht --------
>> Datum: Fri, 12 Aug 2011 09:33:33 +0200
>> Von: tommoni <tommoni_at_email.domain.hidden>
>> An: lisalist_at_email.domain.hidden
>> Betreff: Re: Lisa repair questions
>
>> Hi guys!
>>
>>> the cops chip is in the keyboard.
>>
>> no, definitively not!
>>
>> The Lisa keyboard does not have a COPS inside, but perhaps you think
>> of something what we call a PRAM chip nowadays. This isn't exactly
>> what the engineers built in to store the data inside, telling the
>> system software what kind of keyboard is plugged in, when you fire up
>> your Lisa and the selftest was done.
>> It's a kind of... let's say: E-Prom containing data about the
>> "nationality" of the keyboard e.g. whether you have a standard
>> "qwerty" also known as u.s. layout or e.g. a german "qwertz"
>> keyboard.
>>
>> Some of you guys here in the LisaList know that I'm resident in
>> germany/europe. That's why I own several different types of keyboards
>> for the Lisa and know the differences.
>>
>> But, if you think that the whole keyboard-layout is stored in that
>> device inside the keyboard, you're wrong. As far as I know it's only
>> a 4 bit code, which is transfered to the Lisa short after booting.
>> After that, the Lisa even changes the language in the menue-bar due
>> to that keyboard-code.
>>
>> So Rudi, use a "german keyboard" and after that boot with an "english
>> keyboard" and you will see some different system menues, although
>> using the same Lisa OS
>> I think you asked me that some years ago, when you picked up the Lisa
>> spareparts and the power supplies here in southern Bavaria.
>>
>> The second problem (in fact it's your problem #1) with the automatic
>> shut-down is caused by the little board inside the psu, which watches
>> the correct voltage. It's a safety unit to prevent damage due to
>> overvolt or overcurrent, but also to inhibit start, if there's an
>> undervolt situation. These parameters are all monitored analogue in
>> the secondary part. As far as you know, there's not monitoring in the
>> primary voltage section... do you remember ;-)
>> But what causes such an overvolt or undervolt situation after a few
>> minutes?
>> Replace the electrlyt-caps in secondary voltage unit, located near
>> the output pins of the psu-board; they must be bad due to their
>> age... they're dry for shure.
>>
>> All this has been reported several times in the LisaList a few years
>> ago, but I think it's hard to find if you don't search for several
>> keywords or for a longer time than 5 minutes :-)
>>
>> ...and the psu doesn't have a specific temperature sensor.
>>
>> greetings: TOM from Bavaria, the center of europe, the country with
>> the marvellous castles of Koenig Ludwig, the alps and the original
>> Octoberfest in Munich

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