Tektronix 2A63 Instrument Reference Book page 105

RECALIBRATION
(con'd)
The frequency of the signal used in steps 10 through 25 of the first method (lO0kc) has been selected to pro-
vide 1 ° or less of phase difference between the two modules at all frequencies up to 50 kc and at all sensitivity
ranges. However, any frequency between about 30 kc and 500 kc may be used, if desired, to give more exact
compensation at a specific frequency, with some sacrifice in compensation at other frequencies. (See item 5
under "Equipment Required.") The second method provides compensation at only a specific selected frequency.
The Type 2A63 module, or modules, must be properly calibrated in accordance with the Instruction Manual
procedure before either method of phase-shift compensation is undertaken. Likewise, the Type 2A60 or
Type 3A75 module must be properly calibrated according to the procedures in its Instruction Manual.
FIRST METHOD (for two Type 2A63 modules)
To mutually phase-shift compensate two Type 2A63 modules, proceed as follows:
1. Insert one of the modules in the left-hand opening of the oscilloscope.
Set its +INPUT AC-DC-GND switch
to AC and its -INPUT AC-DC-GND switch to GND. (You do·not need a module in the right-hand opening
at this point if you are using a 561A. With a Type 560 or 561, install the other module in the right-hand
opening and set its INPUT AC-DC-GND switches to GND.
2. Set the GAIN ADJ adjustments according to the procedure given in the Operating Instructions.
3. Set the VOLTS/DIV switch to 20mVOLTS and apply a 300kc sine wave of lO0millivolts amplitude (peak-
to-peak) to the +INPUT connector. (It is important that you know the amplitude of this signal very
accurately; the frequency is also rather critical. Use auxiliary measuring equipment if necessary.)
4. Set C467 so that the length of the displayed vertical line on the screen is 0.707 times the amplitude of
the applied signal divided by 20millivolts per division. (For a lO0millivolt signal, the line should be
3.5 major graticule divisions long.)
5. Set the VOLTS/DIV switch to 1 mVOLTS and apply a 300kc sine wave of Smillivolts amplitude (peak-to-
peak) to the +INPUT connector. (It is important that you know the amplitude of this signal very accu-
rately; the frequency is also rather critical. Use auxiliary measuring equipment if necessary.)
6. Set C456 (C456 is accessible through vent holes in underneath side of the oscilloscope) so that the length
of the displayed vertical line on the screen is 0,707 times the amplitude of the applied signal divided by
!millivolt per division, (For a Smillivolt signal, the line should be 3.5 major graticule divisions long.)
7. Disconnect the 300 kc signal, move this module to the right-hand oscilloscope opening, and insert the
other Type 2A63 module in the left-hand opening.
8. Set both GAIN ADJ adjustments according to the procedure given in the Operating Instructions.
9. Set both VOLTS/DIV switches to 20mVOLTS, both +INPUT AC-DC-GND switches to AC, both -INPUT
AC-DC-GND switches to GND, and both AC STABILIZED switches to ON.
10. Apply a 100 kc sine wave to the +INPUT connectors of both modules. (This signal is used throughout the
remainder of this procedure; see the discussion regarding its frequency in the introduction to the pro-
cedure.
11. Adjust the output amplitude of the signal generator to produce about 8 divisions of deflection vertically
and horizontally.
12. Adjust C467 of the left-hand module to close the ellipse on the screen,
13. Set both VOLTS/DIV switches to lmVOLTS.
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