Tektronix 561A 10 MHz Oscilloscope (1969)

Back to Tek Vintage Summary Page
BAMA 561A Manual Download Site

Quick Specifications / Photos
Detailed Specifications
Operating Instructions
Misc. Part Numbers

Samples of e-Bay Prices
Tektronix Catalog CostLow BidHigh Bidaverage
$530 (1969) ...
$59.99 (buy it now) 1/1/03 #3103922330 bjoh1972@aol.com (w/3A1,3B3)
no buy ($10.25 < reserve) 1/9/03 #3104796596 adams.robert@worldnet.att.net (works well) (w/ 3A72, 3B3)
$30.09 3/12/03 #2514316542 jay74.cids.net (lights up-w/3A72,2B67) (10 bids $1 start)
$33.00 4/9/06 #7606475472 hbarnes (11 bids $12 start) (w/3A72,2B67- turns on-got 2 lines)
$32.51 (+$26.39 ship) 11/5/07 #200168102999 queeny1955 (4 bids $9.99 start) (tested-works w/3A75,3A1,2B67)
$9.00 (+$50 ship) 7/23/08 #190237597975 govt-supply (1 bid) (untested-missing fuse - w/3A1,3B1)
$9.99 (+~$29 ship) 5/25/09 #320373278217 rlr46140 (1 bid) (get dot on screen-2 tubes don't light up-w/3A74,3B3)
$15.50 (+~$29 ship) 6/28/09 #270412812199 tilemover (4 bids $0.99 start) (w/3A1,3B1-trace shown)
$41.01 (+~$29 ship) 7/24/09 #190322322733 justlikepop (10 bids) (untested-dirty,leather worn off handle-w/3A72,2B67)
$28.00 (+~$45 ship) 7/26/09 #280373007142 mememamia1 (6 bids $9.99 start) (restored-but only shows spot on screen-w/2A,2B67)

  • Indicator Unit - Bandpass determined by plug-ins
  • .
  • .
  • .


    General Information

    The Tektronix Type 561A Oscilloscope is essentially an indicator unit with provision for two of a number of plug-in units. The plug-in unit in the right-hand opening controls the horizontal (X-axis) deflection, and the plug-in unit in the left-hand opening controls the vertical (Y-axis) deflection. The plug-in units can be selected from any of the Tektronix '2' Series or '3' Series groups to privide the desired oscilloscope performance.

    Bandpass, Risetime, Vertical Deflection Factors, Input Impedance, and Sweep Rates are determined by the plug-in units used.

    Cathode-Ray Tube

    Type -- T561(rectangular ceramic-envelope).

    Phosphor -- P32

    Unblanking -- Deflection type, dc-coupled, with grid intensification.

    Graticule -- Variable edge lighted "no parallax" internal graticule. Marked in 8 vertical and 10 horizontal divisions with each major division divided into 5 minor divisions on centerline.

    Accelerating potential -- 3.5 kv.

    Usable viewing area -- 8 divisions vertical by 10 divisions horizontal.

    Deflection plate sensitivities -- 18.5 to 20.5 volts per division vertical, and 17.5 to 19.3 volts per division horizontal.


    Waveform -- Square waves at the line frequency.
    Output voltage -- 0.2 millivolt to 100 volts, peak-to-peak, in 18 steps.

    Accuracy -- Peak-to-peak amplitude within 3% of indicated voltage.

    Risetime -- Typically 4 microseconds.

    Power Supplies

    Electronically regulated for stable operation with widely varying line voltages and loads.

    Line voltage requirements -- 105 to 125 volts, or 210 to 250 volts, rms, 50 to 400 Hz, single-phase ac.

    Fuse -- 2-amp slow-blowing type for 117 volts, 1-amp slow-blowing type for 234 volts.


    Convection air cooled. Thermal cutout interrupts instrument power in the event of overheating.


    Aluminum-alloy chassis and 2-piece cabinet.

    Photo-etched anodized panel, blue vinyl paint over textured aluminum on cabinet.

    Dimensions -- Height 13½ inches, width 9¾ inches, and depth 21½ inches.

    Weight -- 30½ pounds, indicator unit only.

    above excerpts from Tektronix Type 561A Instruction Manual


    The air must be able to flow freely around the instrument so that it may cool. Vacuum tubes should not be operated with envelope temperatures above 150° C when the ambient temperature is at 25° C, or above 175° C when the ambient temperature is at 50° C. The Type 561A can operate in ambient temperatures up to 50° C. If the instrument overheats, the thermal cutout will turn off the power.


    Operation or the Tektronix Type 561A Oscilloscope with two plug-in units in place is much the same as that of a conventional Tektronix oscilloscope with corresponding vertical and horizontal deflection systems. The plug-in units take the place of the vertical and horizontal deflection systems in a conventional oscilloscope; their outputs connect directly to the deflection plates of the cathode-ray tube. The plug-in units can be selected to give the Type 561A Oscilloscope the degree and type of performance demanded of it by a particular application.

    The front and back panels of the Type 561A have controls or switches that affect the display; however, the plug-in units determine the major characteristics of the display.

    Front Panel

    The POWER ON switch permits turning the instrument on or off.

    The SCALE ILLUM. control permits adjustment of the brightness of the graticule markings.
    The FOCUS control permits proper trace or spot focus for most intensity values.

    The ASTIGMATISM control works in conjunction with the FOCUS control, and improves the focus over the entire crt display.

    The INTENSITY control permits changing the crt display brightness.

    The ALIGNMENT control permits electronically tilting the level of the crt trace to agree with the horizontal graticule markings.

    The 18-position CALIBRATOR switch determines the peak-to-peak amplitude of the signal at the CAL. OUT connector. It also permits turning the CALIBRATOR off. The calibrator output is used to set the gain of the amplifier plug-in units and to check the basic timing of the time-base units.

    Display Combinations

    The plug-in unit in the right-hand opening of the Type 561A controls the horizontal (X-axis) deflection of the crt beam. The unit in the left-hand opening controls the vertical (Y-axis) deflection.

    To obtain the conventional display of a horizontal sweep with vertical deflection by the input signal, insert a time-base plug-in unit on the right and an amplifier unit on the left. If a vertical sweep is desired with the input signal displayed horizontally, insert the time-base unit on the left and the amplifier unit on the right. If an X-Y display is desired, insert amplifier type plug-in units in both plug-in openings.

    above excerpts from Tektronix Type 561A Instruction Manual
    366-113Knob, Small, Charcoal (INTENSITY)
    366-113Knob, Small, Charcoal (FOCUS)
    366-117Knob, Large, Carcoal (CALIBRATION)
    366-113Knob, Small, Charcoal (SCALE ILLUM)
    SW601260-014Toggle Switch (Power ON)
    R833311-3142 meg (Intensity)
    R84311-3135 meg (Focus)
    SW870260-253Rotary (CALIBRATOR)
    R601311-05550 ohm Var. (Scale Illum.)
    V859154-400T5610-31-1 CRT P31 Phosphor (T561)