logic probe

From: Joe <rigdonj_at_intellistar.net>
Date: Wed Feb 25 07:40:15 1998

Is that for use on your Altair?! Around here that's what we would call
the tail wagging the dog!

   Joe


At 09:57 PM 2/25/98 +1100, you wrote:
>I asked my boss if he had a logic analyzer i could beg borrow or buy... his
>reply below.
>
>> Do you have a logic probe I can beg borrow or buy?
>
>I have quite a fancy 32-channel 100mhz unit, which I haven't used for many
>months. At around $8000 you would probably prefer to borrow rather than buy
>it... Mine is a 110v unit, so you'd want to remember to use a transformer...
>
>
>So, I'm assuming I'm set for a logic probe. !!!!!!!!!!!!!!!!!!!!!!!!!!
>WOw. Can it make tea and coffee too? At THAT price it better.
>
>Now for the Multimeter :)
>
>Cheers
>A
>
>
>
>
>
>
>-----Original Message-----
>From: Tony Duell <ard_at_p850ug1.demon.co.uk>
>To: Discussion re-collecting of classic computers
><classiccmp_at_u.washington.edu>
>Date: Wednesday, February 25, 1998 10:13 AM
>Subject: Re: a brain... my kingdom for a brain?
>
>
>>>
>>> Tony's comment, below... about the only equipment needed to repair... was
>>> helpful.
>>> So, as I have an Altair, a BBC, a KIM, a Sorcerer and various other
>beasties
>>> awaiting ressurection, and having little (well, OK... no) electronics
>>> experience, starting at square 1...
>>> a) What should I be looking for in a logic probe. Any recommended models
>>> (say, <$100)
>>
>>I did a lot of repairs using a very cheap Tandy/Radio Shack/Micronta
>>logic probe, which was officially a 10MHz unit (although it would do a
>>bit more than that). It only cost about $25, I think. Note that there's a
>>logic pulser (the equivalent of a signal injector) in the same range
>>which is a lot less useful than the probe, so if you go for this one make
>>sure you're buying the right unit.
>>
>>HP make some beautiful logic probes, but alas I've never seen one cheap
>>enough to be worth buying. They do turn up at radio rallies, though.
>>
>>It's 8 times your price range (!), but the HP LogicDart is excellent if
>>you are serious about repairs and doing new designs. Probably total
>>overkil for repairing micros, though.
>>
>>As regards specs, all you really need are TTL thresholds (you don't find
>>much else in micros - ECL is useful for some minis and workstations, but
>>few cheap logic probes have that), and pulse detection down to (say)
>>100ns or better. Just about any logic probe will do.
>>
>>> b) Ditto for multimeter.
>>
>>Again, you don't need too high a spec - high accuracy is not that useful
>>in most digital work.
>>
>>Analogue or Digital display is fine. I have both - the analogue meter is
>>better for looking at
>>What you need are :
>>
>>DC voltage ranges up to about 50V (you only need higher voltages if you
>>repair monitors, etc). A sensitivity of 20000 Ohms/volt (== 50uA fsd
>>current) for an analogue meter would be fine. Any digital meter would
>>have a low enough input current.
>>Ohms - especially a good continuity tester. A lot of faults are broken
>>wires, defective switches, etc. Make sure the continuity tester responds
>>quickly - you want to be able to clip on probe onto (say) a connector
>>pin at one end of a cable and run the probe down the pins at the other
>>end. If you have to stop for a few seconds on each pin you'll soon go mad.
>>
>>Again, that's a pretty low spec. AC voltage (up to mains) is useful for
>>checking transformers in linear supplies. Current ranges can be handy for
>>checking PSU load, etc. But I would estimate that 90%+ of all my
>>measurements are either DC voltage or resistance.
>>
>>If you can afford it, get a Fluke (a 77 or a 79 would be _very_ nice).
>>AVO is another good brand. And although I've never used one, there's a
>>meter from Tektronix which is probably good.
>>
>>If those are out of your price range, then just about _any_ digital meter
>>costing about $50.00 would be fine. It won't be as robust as the Fluke,
>>it won't be as accurate. But it'll be enough for most repairs.
>>
>>A recomendation. Get a cheap-ish meter like I've just recomended. When
>>you get more experience and want something better, get the Fluke. Put the
>>cheap one in the car for checking bulbs/battery/fuses/etc when you break
>>down.
>>
>>
>>> c) Where can I find a brain? :)
>>
>>I wish I knew :-). Mine needs upgrading :-)
>>
>>If you want a book recomendation, try 'The Art of Electronics' by Paul
>>Horrowitz and Winfield Hill. There's also a practical book 'The Student
>>Manual for the Art of Electronics' by (I think) T. Hayes and P.
>>Horrowitz. These books cover everything from resistors to
>>microprocessors, and have an intuitive rather than mathematical approach.
>>But you won't 'grow out' of them - there's a lot of good sound
>>information in there.
>>
>>> Actually, the Altair will be my first task. I'm thinking of #1 taking
>out
>>> all the boards. Good idea?
>>
>>Indeed. Pull the boards and clean all the edge connectors (and just about
>>any other metal-metal contact).
>>
>>-tony
>>
>>
>
>
Received on Wed Feb 25 1998 - 07:40:15 GMT