Tek 2230 'scope

From: Richard Erlacher <richard_at_idcomm.com>
Date: Fri Jul 21 19:04:45 2000

I'd recommend you ask to have the instrument "cleaned and adjusted" rather
than "calibrated" since calibration is much more costly due to the
certification cost, but cleaning and adjustment ensures that all the
internal adjustments are brought as close to ideal as possible, certainly to
nominal specification, and cleaning the pots and switches doesn't hurt. The
instrument is given a more thorough "going-over" than for calibration, which
merely requires that all the scales are within specifications. An
attennuator that's out of adjustment but still nominally "within specs"
won't necessarily be cleaned or adjusted.

Dick

----- Original Message -----
From: Chuck McManis <cmcmanis_at_mcmanis.com>
To: <classiccmp_at_classiccmp.org>
Cc: John Foust <jfoust_at_threedee.com>
Sent: Friday, July 21, 2000 3:11 PM
Subject: Re: Tek 2230 'scope


> 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 - 19:04:45 BST