how to troubleshoot? Not all of us have trustfunds!

[Scott Gravenhorst]

I have to agree with Harry.  And after all, everything we do
has some cost of some sort.  In DIY electronics, it's some
cash spent for decent tools.  And as Harry points out, most of
them are one time costs.  At least things like oscopes last
a long time.  They are invaluable IMHO.  Nobody ever said
working with electronics is "free" or even "cheap".  There
just is no guarantee of that.  It's an illusion created by
the fact that some chips are $0.15.  But then some are $20 or
$50.  You won't regret buying an Oscope.

harry <harrybissell at prodigy.net> wrote:
>Are O-scopes necessary...
>
>No. Not if you are willing to bust your ass trying to fix simple
>problems !
>
>Our service department (industrial controls) fixes stuff without scopes.
>
>They tear apart a working unit and swap modules until they get a fix.
>Sometimes they blow up the working unit too... then an auto assembly
>line is down. They call us up crying.
>
>Our first response... "Do you have a scope?"  Usually the answer is..
>uh yeah... out in the car / truck / whatever....
>
>The signal tracer ideas are really good BTW.  If I don't have a scope I
>try
>that.  Its OK for audio amps etc. Fixing high impedance stuff is another
>story.
>Either the loading or the capacitance kills you. SOME circuits will not
>even work
>if you touch them with a scope probe !!!
>
>Get a scope... get a life.  I remember when I was buying my first
>computer... on
>a payroll deduction loan.  A fellow engineer suggested that I tell my
>wife that the
>computer will pay for itself out of "increased future earnings". He was
>FVCKIN-A
>correct. My salary jumped the price of that computer that very year.
>Knowing how to
>work the tools of the trade will increase your value to an employer.
>
>And get to KNOW how to use the scope. Its not just pretty pictures. Its
>a window
>into a world we do not usually see.  Expecting an oscillator and have a
>flat line?
>Expecting DC and have oscillation ?  Your "audio" range listening
>devices will not
>help with ultrasonic oscillations !!!   You meter will not help you.
>Your logic probe
>(very likely) will not help you.  The chip you just put your finger on
>is burning hot...
>Why ???
>
>Get out the scope !!!  Buy beg borrow or steal one ! Get an old one...
>whatever.
>Why bust your own ass willingly.  You will buy one once in maybe 10-20
>years !
>So $200 today is what... $10 a year ???  You blow that on booze and
>women in
>one night   (well... if you are a "big spender"... that is...)
>
>H^) harry   (just MHO)
>
>RFAHL wrote:
>
>>
>>
>>      Are oscilloscopes really necessary for troubleshooting?
>>      They sure as hell simplify the process, but come on.... with
>>      a little ingenuity, there's ways to get by without one.
>>
>>      The circuit in question is pretty simple - a bandpass filter
>>      that gets popped  by a pulse and resonates as a result, like
>>      a stick hitting a hollow drum.  The circuit has an input and
>>      an output.  If you have other similar circuits on the board
>>      that are working you can tap an input trigger from a working
>>      circuit and pump it into the circuit that's got the
>>      problem.  Same goes for the output of the circuit.  You can
>>      use a wire to connect the output of the "bad" circuit to the
>>      input of one of the mixers from a different section.  Just
>>      simple ways to use what's right there in front of you (and
>>      two cents worth of wire).  I've used this type of technique
>>      connecting working satellite receivers to non-working ones
>>      to track down problems. This circuit is far simpler, so I
>>      don't see why this approach wouldn't work.
>>
>>      Couldn't you make a simple logic tester to test for pulses
>>      using a simple LED connected between pulse input and ground?
>>
>>      Also, couldn't you use an audio cable as a probe between the
>>      circuit and an audio amp (with a DC blocking cap for
>>      protection), using your ears instead of your eyes?
>>
>>      Just some thoughts... it's nice when you have money to spend
>>      on tools, but not everyone's in that kind of position.
>>
>>      -------------------------
>>
>>      ElmacacoX at aol.com wrote:
>>
>>           Ok,  thanks for the many replies guys, but an
>>           oscilloscope is way outta my
>>           reach right now.  so, how do I test for faulty op
>>           amps, capacitors,
>>           transistors with my little DMM?  the tip on the
>>           transistors being two diodes
>>           in a three legged race is a good start for me!
>>
>>           thanks
>>
>>           Eduardo
>>
>>
>>
>

-- Scott Gravenhorst : Done the Edge, Now What?
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