I know of a guy who repairs "classic" music
synthesizers who says that virtually every 4000 CMOS
chip from the original RCA masks has or is about to
fail from static problems/metal creep. This includes
most mid 1970's era chips. Fortunately, not much of it
in an Altair, as I recall.
--- "Kapteyn, Rob" <kapteynr_at_cboe.com> wrote:
> All good advice so far -- but one caution I forgot.
>
> My experience is that the CMOS chips from this
> period are THE MOST STATIC
> SENSITIVE chips that there are.
>
> It is much easier to damage these whith
> inappropriate handling than any
> modern stuff.
>
> Use paranoid static handling precautions.
> Since I usually work on these machines on those cold
> (dry) winter days when
> static forms easily,
> I also use a humidifier in the room where I work.
>
> -Rob
>
>
> -----Original Message-----
> From: cctalk-admin_at_classiccmp.org
> [mailto:cctalk-admin_at_classiccmp.org]On
> Behalf Of J.C. Wren
> Sent: Tuesday, September 24, 2002 8:08 PM
> To: cctalk_at_classiccmp.org
> Subject: RE: Altair-what do I do first
>
>
> A less painful way may be to lift the output pin of
> the regulator
> from its
> via. Or (and this is evil, but works, and is can be
> better than losing all
> your unsocketted chips), cut the trace after output
> of the regulator. You
> can always use a piece of foil tape or wire to
> effect a repair. This may
> detract from the ultimate value of the board, but
> you're far less likely to
> wreck it than removing irreplacable socketted chips.
>
> --John
>
> -----Original Message-----
> From: cctalk-admin_at_classiccmp.org
> [mailto:cctalk-admin_at_classiccmp.org]On
> Behalf Of Tony Duell
> Sent: Tuesday, September 24, 2002 20:24
> To: cctalk_at_classiccmp.org
> Subject: Re: Altair-what do I do first
>
>
> >
> > Good move -- don't plug it in yet.
>
> _Neve_ plug in a classic computer without checking
> it first!
>
> [Good advice on electrolytic caps deleted]
>
> > In any case, detach everything from the power
> supply and check it out
> first.
> > Unfortunately, Altairs have no connectors for
> this, so you will have to
> > desolder the wires.
> > Some suggest powering it up slowly on a variable
> transformer, but I have
> not
> > tried that.
> >
> > After checking out the power supply voltages,
> unplug all of the cards and
>
> The amin problem with S100 systems is that the PSU
> lines on the bus are
> unregulated. The voltage regulators are on each
> card. And this means that
> a defective regulator _on a card_ will wipe out all
> the chips on that
> card, and may even put high voltages onto the bus
> lines and damage other
> cards.
>
> Therefore, do as suggested and get the unregulated
> PSU working first.
> Then take the cards (one at a time) and remove all
> socketed ICs. Make a
> diagram first, of course if you don't have the
> schematics/layout diagrams
> for that card. You'd better hope that the
> expensive/rare ICs (CPU, ROMs,
> RAM, LSI I/O chips) are socketed.
>
> Then put the (essentially bare) card in the
> backplane and check the
> outputs of the regulators on that card. Repeat for
> all the cards you
> have. Put the ICs back into a card before starting
> on the next one
> (unless you are a lot better organised than me!)
>
> Then, and only then do you put populated cards into
> the backplane and
> start testing logic functions.
>
> -tony
>
>
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Received on Wed Sep 25 2002 - 11:54:00 BST