Re: My Lisa 2 got a defect Monitor

From: Scharpf Thomas <thomas_at_email.domain.hidden>
Date: Tue, 09 Oct 2001 20:23:52 +0200

Thank you James, that's exact what I intended to explain... ...and a big "excuse me" for my bad english, but we talk here german, french and italian and english of course but the technical english is full of problematic words, which I don't really know by brain and my dictionairy doesn't, too.
You're totally right: A Lisa could be a dangerous computer concerning the rest of high voltage when the power plug was pulled out. Sometimes even quarter an hour later the voltage is still so high, that it could be lethal. The fault itself is very likely a bad flyback transformer (I now know the expression my dictionairy couldn't tell me), as I wrote I had the same error on a Lisa of mine. The video board was in working order, the I/O board, too. I changed the transformator, it's only fixed with one screw at the bottom and the dead Lisa worked again. Since that day I'm searching for a spare transformer, but there are a few availlable with same rating and electrical data, I will try out, if I get some spare time in future...

keep on loving Macs in a sWINdler's world

---

>Von: James MacPhail <uo957_at_email.domain.hidden>
>An: <lisalist_at_email.domain.hidden> (LisaList)
>Betreff: Re: My Lisa 2 got a defect Monitor
>Datum: Mon, 8. Okt 2001 22:19 Uhr
>

>
>>i have no idea what you're talking about! Explain in plain english
>>please. i know almost nothing about them and i just got them!!
>
> Thomas made a very good attempt to translate into English, however if you
> are not familiar with the subject, it can be hard to interpret.
>
> Thomas wrote:
>>>I got a similar fault with one of my Lisas. The monitor kept being totaly
>>>death, although the tube was fired with the whole low voltage, but not the
>>>high-voltage from the HV-transformator at the left side under the tube, when
>>>looking from top of it. Answer my question: does your HV-transformator
>>>whistle or not? If not, it's probably dead like mine. You can plug it of
>>>(the fat HV-cable to the tube and the 6 wire plug to the monitor board) and
>>>change it (from another Lisa, perhaps) and try. In my case it works again
>>>and since that time I'm looking for some parts to replace
>
> Here is an attempt at a translation... probably still hard to understand.
>
> "I had a similar problem with one of my Lisas. The monitor was dead. The
> tube was receiving low voltage power (so the filament would light up), but
> no high voltage from the flyback transformer (under the tube on the base of
> the chassis). Does your high voltage transformer whistle? If not, it is
> probably dead. You can unplug it (the fat HV cable to the tube and the 6
> wire plug to the video board) and replace it. In my case, this solved the
> problem, so now I'm looking for spare parts."
>
> My comments...
>
> 1. Messing with the High Voltage can be lethal and deadly or even kill you,
> even with the line cord disconnected! If you are not familiar with working
> on TVs or Monitors, you should get someone who is experienced to help. If
> you are in a remote area and help is not available, ask for specific safety
> instructions.
>
> 2. The whining of the flyback transformer is created by the switching
> current from the video board. No whining may mean the video board is
> defective or not receiving the correct power and signals, so I think that a
> bad flyback transformer is not the only cause of this symptom.
>
> 3. In Alex's case, it seems unlikely that the flyback would be damaged by
> connecting an external monitor, however it may be a coincidence that it
> failed at that time, so the flyback may be bad anyway.
>
> HTH,
>
> James
>
>
> James MacPhail "Think not of engineering as art,
> uo957_at_email.domain.hidden but of art as engineering"
> Sigma Seven Systems Ltd.
> james_at_email.domain.hidden <http://SigmaSevenSystems.com>

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Received on 2001-10-09 11:48:23