Tek 2230 'scope

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Fri Jul 21 16:11:46 2000

At 10:24 AM 7/21/00 -0500, John Foust wrote:
>I picked up a Tek 2230, a 100 MHz two-channel digital storage oscilloscope
>for $150 today, on a rolling stand. It shows signs of life in the sense
>that the display works and the buttons seem to have some effect, like
>stepping through menus.

This is a nice find. The 2230 is an ok scope, it does have some issues but
for vintage work they won't be a problem.

The easiest way to get it "checked out" is to take it to a calibration
laboratory and get it calibrated. This is something you should do on your
scopes, especially if you use them for adjusting other things (like drive
head alignment). It will cost between $75 and $150 usually for a
calibration but when you get the sticker on your scope it will both raise
the value (known good), and assure you that you've got a working scope.

>Where do I begin?

Plug a probe into channel 1 and then clip the hook to the little bar in the
front of the scope that set "cal" or "test" or whatever. It should be
metal. Tek puts a calibration signal (60hz on older scopes). Then set the
trigger option to "internal" and make sure the single sweep button is "out"
or disengaged. You should see a sine wave on the screen. Adjust the
amplitude using the channel amplitude adjust and the number of waveforms on
the screen with the time base knob (marked in time increments)

Scopes are very simple think of them as a piece of graph paper with
automatic writing :-), they work like this:
         - There is a screen that has lines on it like graph paper. Each
square is one "unit"
         - The screen is written to with a beam, the beam is deflected
upward and downward by
           voltage, and deflected left to right by time.
         - Each channel writes one line on the graph paper.
         - The value of the units on the graph are controlled by two knobs:

                 One controls voltage sensitivity for a channel, when it
                 reads 1V it means that one unit of deflection of the beam
                 means the probe is measuring 1 volt.

                 One controls the time it takes the beam to go across the
                 screen (called the timebase) when it reads 10nS it means
                 that the beam travels from the left edge of one unit to
                 the left edge of the next in exactly 10nS.

         - There is a circuit called the trigger circuit that tells the
oscilloscope
           when to start the beam. When it is set to "line" it usually starts
           60 times per second (or 50 times in Tony's UK case).
         - You can also set the trigger to fire based on the voltage seen
by one
           of the channel probes. The two values you set are :

                 Threshold - The voltage at which the beam will
                         trigger. When the probe sees this voltage
                         it will trigger the beam to cross the screen.

                 Rising/Falling - When set to rising the trigger occurs
when the
                         voltage starts out below the threshhold and crosses it
                         going up. When set to falling it triggers when the
                         voltage goes past the threshold falling down.

           In computer circuits this is often the "rising edge" or the
"falling edge"
           of some clock pulse.

         - Single Sweep is used if the trigger is not supposed to reset
automatically
           and it very useful in glitch detection and for storage scopes.

To use a scope as a DMM:
         Set the trigger to 'line' and the time base to 10mS. You should
see a bright line
         across the screen. Set the probes sensitivity 1/5 of the voltage
you expect to measure
         (for a 5v measurement set it to 1V). Now when you touch the probe
to a wire the
         line on the screen will move up (or down for negative voltages)
some number of
         units. Count them off, including the fraction. Multiply by the
voltage setting and
         that is the voltage you are seeing.

         To measure 'ripple' on the line, set the probe to "AC" coupling.
This puts a
         capacitor in series with the probe so that any DC value is
eventually zeroed
         out as the capacitor charges. Now crank down the sensitivity to
10mV or less.
         See the bumpy line? That is signal "ripple" on your power supply.
If it is
         more than a few percent of your regulated voltage then thats a
problem.

To use a scope as a frequency counter:
         Place the probe on the signal to be measured (DC coupling), set
the trigger
         to be channel 1 (or 2 if you are using a probe on channel 2) then
adjust
         the threshold until you either get a waveform display your you get
a band
         of green. If you get the band crank the knob on the timebase until you
         can see at least one complete waveform on your screen. Now use the
horizontal
         postion knob to slide some recognizable point (perhaps the lowest
point) of
         the waveform to set right on top of one of the graticule lines.
Now count
         units (including the fractional unit at the end) until you get to
the same
         point on the waveform. Multiply by the number on the timebase knob
to get
         the 'period' of the waveform. Take 1 and divide it by that number
to get
         frequency.


They are really very versatile and useful instruments.

>Was this a good deal?

If it is fully functional it is an excellent deal.


--Chuck
Received on Fri Jul 21 2000 - 16:11:46 BST