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Re: Unreliable Hardware

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  • Richard
    In the last weeks I was a bit busy at work and had only little time too take a look here. My old Elf II is still functional after more than 30 years. It used
    Message 1 of 11 , May 31, 2010
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      In the last weeks I was a bit busy at work and had only little time too take a look here.

      My old Elf II is still functional after more than 30 years. It used to have a Quest Super Expansion and our old cat back then used to take a nap on the nice warm 2101 RAMs. This fortunately was no problem because kittie only came when the computer was running and the RAMs were warm.

      Apart from cats the old computer survived a lot, even being taken apart and wrapped in towels by my unknowing parents when I left for military service. Before it withstood my soldering skills and various 'improvements'.

      It actually is in good shape except for some aging connectors, sockets and worn out keys. Only during my recent move I must have zapped some simple 40xx logic on the Quest board with the address displays and the interfaces for other Quest stuff.

      But I have one good tip: PC cards usually come in antistatic bags. Keep them and put the Elf's components into them when you take it apart. The bag for a PC mainboard will easily do for the bigger boards. In there the components will be safe from static and dust and the better ones are even cushioned. This is much better than tin foil.

      --- In cosmacelf@yahoogroups.com, "awasson2001" <awasson@...> wrote:
      >
      > Hmmm,... I'm not so sure if cloth and plexi are such a good combination around static sensitive chips. It could make a very effective Van de Graaff static electricity generator.
      >
      > Andrew
      >
      > --- In cosmacelf@yahoogroups.com, "Agustus Finknottle IV \"Gussy\"" <john_crane_59@> wrote:
      > >
      > > Allison,
      > >
      > > Yes, I definitely agree with you on the sockets. I have a SWTPC 6800 that had a CPU card with those cheap side wipe sockets. Extremely tempermental! I eventually replaced all the sockets with modern machined pin sockets. Not vintage, but at least the system works. As for the ELF, the sockets are good and there's no corrosion.
      > >
      > > Mark,
      > >
      > > Good point. I'll start replacing with CMOS B. No cats or sunlight, but it does have the nice metal case. This comes with a clear plexiglas box that's a dust cover for the expansion cards. And I do keep a towel over the unit to keep dust off when it's in storage. I'm wondering now if the towel moving across the plexiglas may have generated some voltage. Maybe I should store everything disassembled and wrapped in foil?
      > >
      > >
      > >
      > > -John
      > >
      > >
      > > --- In cosmacelf@yahoogroups.com, "ajparent1" <kb1gmx@> wrote:
      > > >
      > > >
      > > > The greatest source of pain in kits is soldering.
      > > >
      > > > After that for things like bad sockets, switches with oxidized contacts and foreign material on the board causing high resistance
      > > > shorts.
      > > >
      > > > As to sockets.. I have a collection of OLD (ranging from 1973
      > > > to 1985) machines and there was a window in time in the when
      > > > TI and RN (and others) made some really cheap side wipe sockets
      > > > that tend to fail with what amounts to contact fatigue, they stop
      > > > making contact to the IC pin or become very intermittent.
      > > >
      > > > Also any kit using CMOS may be prone to static electricity which
      > > > can cause both immediate failure and also long term failure. If
      > > > not in a case a wrap of Aluminum foil will protect it nicely.
      > > >
      > > > That said my original ELF is going on 32+ years old and still works
      > > > just fine. As are my other machines built in that era (1975 to 1978).
      > > >
      > > >
      > > > Allison
      > > >
      > > > --- In cosmacelf@yahoogroups.com, Mark Graybill <saundby@> wrote:
      > > > >
      > > > > Any chance the blown chips are 'A' series CMOS? If so, perhaps some
      > > > > can be replaced with 'B' series which have better static protection.
      > > > > And yeah, some case-style protection is always a good idea. Especially
      > > > > if it gets sunlight where it's sitting on the shelf, or 50,000 volt
      > > > > cats like checking out your electronics occasionally.
      > > > >
      > > > > -Mark Graybill
      > > > > -----------------------------------------------------------------------------------------------------------------
      > > > > http://saundby.com/
      > > > > Electronics, Books, Video Games, etc.
      > > > >
      > > > > On May 28, 2010, at 10:45 PM, Agustus Finknottle IV Gussy wrote:
      > > > >
      > > > > >
      > > > > >
      > > > > > --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@> wrote:
      > > > > > >
      > > > > > > On 5/28/2010 5:52 PM, Agustus Finknottle IV "Gussy" wrote:
      > > > > > > > I swear my little Elf II is the most unreliable computer I've ever
      > > > > > > > owned. It's the only machine I know of that can "break" simply by
      > > > > > > > sitting on a shelf. Every couple of months I decide to get it out
      > > > > > > > and do some work, and every time I have to repair something that
      > > > > > > > mysteriously "died" while it was on the shelf. I fix everything,
      > > > > > put
      > > > > > > > it away, and repeat the process 2 months later. Does anyone else
      > > > > > > > have this problem?
      > > > > > >
      > > > > > > What exactly has broken? Are the same things breaking, or
      > > > > > something new
      > > > > > > each time? Bad solder joints? Cheap sockets?
      > > > > > > --
      > > > > > > Lee A. Hart | Ring the bells that still can ring
      > > > > > > 814 8th Ave N | Forget the perfect offering
      > > > > > > Sartell MN 56377 | There is a crack in everything
      > > > > > > leeahart earthlink.net | That's how the light gets in -- Leonard
      > > > > > Cohen
      > > > > > >
      > > > > >
      > > > > > Hi Lee,
      > > > > >
      > > > > > The last 2 times it was different dead chips. And I recapped
      > > > > > everything back in 2007. This time I got it out to work on a new
      > > > > > monitor program I wanted to put in a ROM. And the existing monitor
      > > > > > on the Giant Board simply refused to accept keyboard input. I'm sure
      > > > > > I can track down the fault. I just felt a little disgusted as it was
      > > > > > working perectly when I set it on a shelf a couple of months ago.
      > > > > > And it keeps "dying" in storage. I have other vintage machines and
      > > > > > they don't get zapped like the Elf. Maybe I need to build a grounded
      > > > > > steel cage and put it in there for safekeeping. It was my very first
      > > > > > computer, so I like to try to keep it in good running condition.
      > > > > >
      > > > > > I haven't taken it apart yet to examine anything. Of course it may
      > > > > > not be a dead chip this time.
      > > > > >
      > > > > > -J
      > > > > >
      > > > > >
      > > > > >
      > > > >
      > > > >
      > > > >
      > > > > [Non-text portions of this message have been removed]
      > > > >
      > > >
      > >
      >
    • thinkpast
      ... I d have to inspect the physical geometry, but it sure SOUNDS like you ve created a capacitor and are charging it up with the towel! Charges build up on
      Message 2 of 11 , Jun 2, 2010
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        > --- "Agustus Finknottle IV \"Gussy\"" <john_crane_59@> wrote:
        >
        >> Good point. I'll start replacing with CMOS B. No cats or
        >> sunlight, but it does have the nice metal case. This
        >> comes with a clear plexiglas box that's a dust cover
        >> for the expansion cards. And I do keep a towel over
        >> the unit to keep dust off when it's in storage.

        >> I'm wondering now if the towel moving across the
        >> plexiglas may have generated some voltage.
        >> Maybe I should store everything disassembled and
        >> wrapped in foil?

        "awasson2001" <awasson@...> wrote:
        >
        > Hmmm,... I'm not so sure if cloth and plexi are such a
        > good combination around static sensitive chips. It
        > could make a very effective Van de Graaff static
        > electricity generator.
        >
        > Andrew

        I'd have to inspect the physical geometry, but it sure SOUNDS like you've created a capacitor and are charging it up with the towel! Charges build up on the inside of the plexiglass, and "induce" a charge on the PC board underneath by electrostatic attraction. If the plex is charged "positive" underneath, it would attract "negative" charge from the circuit board.

        The charge has to find a discharge path, and it may be through your chips to some kind of "ground" path if the board and its power supply is not plugged in. If there are cables attached, it may discharge through the cables to some point of attachment. Or discharge at the sharpest corner or wire or point into the air. Sharp objects discharge quickly, flat surfaces slowly, has to do with electric fields and such.

        Static electricity is a funny world - it's not about "current flow" but about charges moving around, very high voltages but almost no "current". CMOS is also funny stuff, especially the early chips which were pretty sensitive to it, before they added feature to limit static discharge. (I'm an old Electrical Engineer so I remember this stuff from when it first was done. CMOS that is, not static electricity!)

        If you want to experiment, create a similar physical layout, but put a PC board in place of the cards. Most any board, populated or not will do - just be sure you never want to use it again if it has components.

        You'll need a neon lamp of some sort, from Radio Shack or salvaged from a 110 Volt "self illuminated" switch, etc. etc. (An LED needs too much current.) Attach it to the PC board on it's "ground" or "power" lines (or just the blank board copper) and ground the lamp through some resistor of a few hundred Kohms (or none it just limits current). A "ground" would be, oh, say any convenient pipe or metal object, chair or table, etc. I would not suggest a wall socket ground, don't want to create something at risk.

        Then stroke the plastic in darkness with the towel, and watch the neon lamp!

        Clever experiments aside, I imagine you could cover the plexiglass with some translucent "antistatic" sheet cut from an antistatic bag, and attach a clip to that bag to the chassis the "window" is mounted on. I'm not sure if you can put the sheet on the INSIDE surface and accomplish the same thing.

        If your plexiglass is an open box acting as cover, you may try replacing it with a wood cover, or a metal cover, or just cover the unit with an antistatic bag (open or closed) and see if the problem goes away. If transparency is important, you might make a wood or metal cover with a "window" of plex or antistatic sheet.

        I probably don't know for sure how your cards are boxed, but I hope from the descriptions above, you have some ideas as to what to consider.

        Herb Johnson
        retrotechnology.com
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