Tektronix Webcam 070-8030-01 User Manual

Troubleshooting Procedures

1780R-Series Service Manual

4. Set the 1780R-Series instrument POWER switch to ON.

5. Set the 1780R-Series front-panel controls for best viewing of the color bar

vectors on the Vectorscope CRT and of the waveform displayed on the
Waveform CRT. Turn the SCALE control to obtain the highest level of
illumination for both CRT graticules.

6. Set the autotransformer to low line (90 V for 115 VAC operation; 180 V for

230 VAC operation).

7. Set the 1780R-Series POWER switch to OFF (STANDBY). Connect the

180

W, 10W, resistive load between the top end of A2L638 and chassis

ground. Miniature alligator clips may be used for connecting the load
between A2L638 and ground. (The +60 V supply is applied through A2L339
to the top end of A2L638; see Diagram <6>.)

8. Turn A1R466 fully clockwise (maximum resistance). Then, turn this

adjustment counterclockwise about one-third of its rotation range. Set the
POWER switch to ON.

9. ADJUST Current Limit Adj (A1R466) slowly counterclockwise until stable

operation is obtained. Typically, stable operation occurs near the center of
the adjustment range.

10. Set the instrument POWER switch to OFF (STANDBY). Disconnect the

resistive load. Set the POWER switch to ON and check for stable operation
at low line. The instrument should operate normally.