5. MAINTENANCE. ORTEC 462

7

Fig. 4.1. Typical Biased Timing Spectrum with Time

Markers Spaced for 10 ns.

Fig. 4.2. The Spectrum of Fig. 4.1 with Dispersion.

5.1. GENERAL

The following paragraphs are intended as an aid in the installation and checkout of the 462 Time

Calibrator. These instructions should provide ample information to ensure that the instrument is operating satisfactorily and to isolate any trouble that may occur.

Test Equipment The following, or equivalent, test equipment is needed.

!

Fast Oscilloscope, such as Tektronix 454, 581, or 585 Voltmeter.

!

Scaler with accurate time base, such as

ORTEC 715 .

Preliminary Procedures Visually check the module for possible damage due to shipment or handling and then perform the following steps:

1. Connect ac power to a nuclear-standard bin and

Power Supply such as the ORTEC 4001/4002

Series.

2. Plug the module into the bin and check for proper mechanical alignment.

3. Switch the ac power on and check the dc Power

Supply voltages at the test points on the 4001

Power Supply control panel.

Frequency and Countdown Tests The following procedure should be used for frequency and countdown tests:

1. Connect the oscilloscope to the PERIOD output

BNC on the rear panel with 50

Ω

cable and with a 50

Ω

termination at the oscilloscope.

5. MAINTENANCE

2. Set the time base of the oscilloscope at

50 ns/cm and the vertical deflection for

200 mV/cm. Use dc coupling.

3. Apply power to the 462 and switch it on. The front panel lamp should light to show an operational condition.

4. Set the PERIOD switch at 0.01 (

µ s) for 10-ns pulse intervals. Observe 5 pulses/cm with an amplitude of

!

600 to

!

800 mV. This is the basic oscillator output at 100 MHz.

5. Change the PERIOD switch setting to each of its other positions, and monitor the square wave output for each switch setting. Each setting should provide a 1-cycle output that has a period matching the switch setting, and the nominal amplitude should stay at about

!

800 mV.

6. If a scaler is available, monitor the frequency of the PERIOD output to verify the output rate.

Some typical trouble symptoms, together with means of determining and correcting them, follow:

1. No output for any switch position; oscillator probably inoperative. Check for ~–1.3 V on pin 5 of IC1. Check for

!

5.2 V ±0.2 V on pins 2, 3, 4,

9, 11, and 12 of IC1. Change IC1 if the voltages are incorrect.

2. No output on 0.32

µ s or any succeeding larger period setting; ECL-to-TTL translator not operating properly. Check Q2 and Q3 by observing a 0- to +5-V square wave on the collector of Q3. Check outputs that switch from about 0 to +5 V on pins 12, 9, 13, and 8 of IC4 through IC8. Check input to TTL-to-ECL translator Q4, Q5, and Q6; check at Q4B for