a brain... my kingdom for a brain?

From: Allison J Parent <allisonp_at_world.std.com>
Date: Tue Feb 24 08:47:56 1998

<a) What should I be looking for in a logic probe. Any recommended model
<(say, <$100)

Unless the logic is fast (altairs arent!) any will do.

<b) Ditto for multimeter.

My favorites are a fluke m12 (digital) and a triplite-160(analog).

<c) Where can I find a brain? :)

think about it for a while ;)

<I have it firing up and basically behaving, but some LEDs don't light whe
<they should, but are definitely able to light when they want to.

Nominal altair misbehavour. Several problems very likely some age and
some design related. Switches are not making(corrosion internally),
operating them may clean them up or replacement may be needed. Check with
low current/voltage continuity tester(fluke m12 is good here). The pannel
uses oneshot timers by the carload (74ls123 and friends) and they can be
flakey. The mother board connections can be nasty from using solderplated
edge connector board with gold edge (electromigration). The board edges
can be cleaned with eraser but most systems with that disease end up with
shake well before using (pull boards/reinsert to wipe contacts).

I highly suggest this for any kit constructed altair pannel:

1. get drawings/schematics
2. clean well
  a. remove and disassemble to just the board with no hardware.
  b. Wash (yes really!) in dishwasher (best done when wife is not around)
     using some of the normal dish washer soap.
   NOTE: this will remove grime and any flux residues that may over time
         have become conductive or corrosive! We have no way of assuring
         a kit was constructed with quality solder/fluxes.

  c. dry well using WARM oven at 120-140F.
     (alternate is to soak in pan of 90% or greater isopropanal and air

3. Inspect and resolder any questionalble joints, use care.

4. Reassemble partially, to allow testing.

       design has 120vAC power on it and that was/is very bad practice.
       As implemented it is a safety hazard and also a risk to the
       hardware. It is best to keep good distances between mains power
       and logic! Rewire so that the front pannel power switch is not
       connected to anything and mount a replacement in a protected spot
       on the rear pannel.

I feel strongly about that, even as a museam peice it should be done. The
existing switch can be left in place for appearances.


<>Hmm... I've yet to find a classic computer fault that could not be
<>tracked down using 3 things - a logic probe, a multimeter (DMM/VOM) and
<>a _brain_. On the grounds that my brain isn't that good, I sometimes hav
<>to use other test equipment, but when I finally do track down the
<>problem, I generally realise that the symptoms were obvious from the
<>start if only I'd realised what they meant.
Received on Tue Feb 24 1998 - 08:47:56 GMT

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