Future technicians will know how to fix it - Re: A stored collection piece is a Schrodinger's cat

Toby Thain toby at telegraphics.com.au
Sat Nov 28 17:03:26 CST 2015

On 2015-11-28 5:24 PM, rod wrote:
> Hi
>      I had the exact same fault on my VAX.
> I took one look at the PSU and ordered up another one pronto.
> Trouble shoot in that small space no thank you.
> It works just fine.  One day a VAX PSU guru will tell us how to fix it.

Indeed, one day we will have the technology! Cryofreeze it until then.


> Rod Smallwood
> On 28/11/15 21:09, Robert Jarratt wrote:
>>> -----Original Message-----
>>> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Terry
>>> Stewart
>>> Sent: 28 November 2015 20:05
>>> To: General Discussion: On-Topic and Off-Topic Posts
>>> Subject: Re: A stored collection piece is a Schrodinger's cat
>>>> I see a big problem with this flowchart, the path on the far right does
>>> not exist, please delete it and then the flowchart will be believable.
>>> ..
>>>> I do think there are not nearly enough arrows pointing upwards
>>> LOL Rob, Mark.
>> I agree with Mark, needs more upwards arrows, more cycles (some
>> without an exit at the bottom). :-)
>>>> Today it's all going to come together and hopefully the outcome will be
>>>> a fully working PET4032 and an extra diagnostic tool to add to the
>>> collection.
>>>> Of course we all know something ELSE unexpected will happen.
>>> Yes, I love the case design of the PET.  It looks just so retro and
>>> '80s futuristic if
>>> you get my meaning...
>>> I designed that tounge-in-cheek flowchart as a kind of catharsis
>>> having just
>>> spent the last three weeks, firstly fixing my Apple II+ which was a
>>> non-starter
>>> on checking (a faulty F8 ROM in that case) then followed by the next
>>> unit I
>>> tested, whose 74LS500 in the video circuit failed after about 5
>>> mins.  I'm almost
>>> afraid to turn on any more...but then...Schrodinger's cat
>>> and all that.   I need to know!
>>> Terry (Tez)
>> I had my own episode last week when I turned on my VAX 4000-500 after
>> a few months of not running it. It ran for a few minutes and then
>> powered off. Now it won't power on for more than a few seconds before
>> cutting out. This is the second PSU to do this to me (the first
>> actually failed outright) and I am wondering if the fault is with
>> something in the machine itself rather than the PSU. Although, now,
>> even with different combinations of boards removed (so there is at
>> least some load), the PSU won't stay on for long, so I don't think it
>> can be one of the boards, but perhaps something in the machine has
>> caused a fault which has now damaged the PSU. I have another spare PSU
>> but I am not going to risk it yet until I have had time to investigate.
>> Regards
>> Rob

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