Aligning System Timing

DANGER This is an advanced and tricky procedure. I'm documenting it here in the hopes that after working through it a few times I'll have all the implicit steps written down. Be aware that changing the timing on any of the units in the system can (a) prevent successful edits, (b) render it impossible to do even simple recording.

Don't attempt this unless you have at least 2 hours of dedicated time to work through it. If you are going to align timing on the entire system, reserve 8 hours. Also note that the Abekas is vastly more difficult than setting timing of any other unit, by about 3X.

Video Switcher Timing

Follow the procedure in the Grass Valley GVG-200-1N Production Switcher Service Manual, Volume 1. This should not have to be done unless the switcher settings get zapped.

Waveform Analyzer Timing

Make sure that the VideoTech TVM-720 Video Analyzer is properly connected, including the CFID (Color Field ID) cable. House master sync reference is connected to input D. Program output from the distribution amplifiers is connected to input C.

1. Select "Color Bars" as the Program output of the switcher.
2. On the analyzer, select Level II, VEC, and then select input C.
3. Adjust the knob to align Y, -I, and Q lines with the marks on the graticule.
4. Do not change the setting of the knob for the duration of the procedure. This has established the proper phase relationship of the analyzer.

Setting VTR Timing

This example will assume that VTR D is the machine being aligned ("timed").

1. Open the silver front cover to the GVG-200 switcher's electronics bay.
2. On the hand-held control unit, press PERS, 12, ENT. The display should read "BLANKING ON".
3. Use the up and down arrows to change the display from ON to OFF. Don't forget to change this back when you are finished. A good reminder is to leave the front cover open for the duration.
4. Select VTR D as the Program output of the video switcher.
5. Insert one of the "Bars & Tone" test tapes into VTR D, rewind it, and press PLAY. Check the monitor to make sure that the color bars have started playing before proceeding.
6. If a Betacam machine, open the front cover all the way up. (The Microtime controls are accessible on the front panel). If a Microtime, ensure that all 4 control knobs are pressed in (default settings).
7. Select VTR D on the yellow "A Background" bus.
8. Select "Color bars" on the yellow "B Background" bus.
9. Select "WIPE" on the M/E Transition control.
10. Select Wipe 0 on the Pattern control. This is a horizontal wipe.
11. Elsewhere in the Pattern control portion of the Grass Valley, turn off effects which will interefere with the calibration procedure.
    • Ensure that H MULTI and V MULTI are both set to 1 (one).
    • Ensure that BORDER ON is not illuminated.
    • Ensure that SOFT ON is not illuminated.
    • Ensure that POS NORMAL is illuminated.
    • Ensure that yellow WIPE is illuminated.
    • Ensure that ASPECT ON is not illuminated.
12. Move the M/E Transition lever to the middle of it's travel.
13. Press the yellow "M/E 1" button as the Program output of the switcher.
14. Ensure that the top half of the wipe is the VTR and the bottom half is the color bars reference. If it isn't, move the transition lever to one extreme and back to the center, until it is. ( Check this. My tests suggest that the VTR needs to be on the bottom half)
15. Observe the Program output on a monitor. There will probably be a left-right shift in the bars halfway down the screen, where the wipe effect transitions.
16. On VTR D, adjust the "Horizontal Theta [Phase]" (Microtime) or "Sync" (Betacam) knob to shift the VTR's bars relative to the reference. Adjust until there is no visible shift, i.e. until the bars are seamless vertical columns. Adjust the knob with the green-tipped plastic screwdriver. This adjustment is *very* sensitive.
17. The waveform analyzer should still be set for Level II, and VEC. There should be two color bar vector plots, overlayed.
18. Use the "Subcarrier Theta [Phase]" (Microtime) or "SC" (Betacam) knob to adjust the two vector plots on the analyzer, until they overlay each other exactly in angle. Don't worry about a small difference in amplitude (radial offset), only angular alignment.
19. On the waveform analyzer press "SC/H". A vertical meter with a triangular pointer should appear. The scale is +/- 40 degrees of phase. At the bottom left of the screen is a numerical readout of the SC/H error. If there is no triangle on the screen, this is the only indication of the error.
20. Go back to the Horizontal Phase adjustment again, and adjust until the SC/H phase error is less than +/- 5 degrees. The adjustment is *very* *very* sensitive. The Betacam machines can be aligned within +/- 1 degree, by brushing your fingertip lightly across the shaft of the screwdriver. (What is being done here is trading off a small error in horizontal position for precise color phase accuracy, to achieve the required SH/H (subcarrier-to-horizontal phase) relationship.
21. Check your results. Ensure that the switcher is still in "BLANKING OFF" mode. Visual inspection of the program monitor should reveal no more than a slight horizontal shift at the wipe. The VEC display on the analyzer should show excellent angular alignment. The SC/H display should show an angular error less than +/- 5 degrees (20 for Microtime). If not, go back and perform the procedure again.
22. Note that on the Microtime, the horizontal phase control is digitally quantized (blech) and the SC/H relationship can only be affected with the horizontal phase control, so the SC/H error can go scooting off +/-70 degrees with a nudge of the screwdriver. I have been unable to get an error of less that 15 degrees with the Microtime TBCs, but the horizontal shift is visually less than on the Betacams with only a 1 degree error. Go figure.
23. Change the scope into waveform (WFM) mode, and select the Lp filter for luminance-only display. Adjust black level so that the blue (rightmost) bar matches, and that the black bar matches at exactly 7.5IRE.
24. Adjust video level/gain to match luma brightess of white and yellow (leftmost) bars.
25. Change the scope into vectorscope (VEC) mode, and match chroma gain and chroma phase. Note: do not use chroma phase as a "hack" in place of adjusting SC phase; when the BLANKING insertion is re-enabled, your hack will vanish and the colors will be all wrong.
26. Congratulations, the VTR timing and calibration have been properly set. If a Betacam machine, close the front cover.
27. If this is the last VTR to have it's timing set, go to the switcher's hand-held control unit and press the up arrow. The display should read "BLANKING ON". Press the "HOME" key, and close the silver front cover.

Setting VTR Audio Playback Levels

This might be a good time to check the audio calibration as well.

1. Insert one of the "Bars & Tone" test tapes into VTR D, rewind it, and press PLAY.
2. On the front of the VTR, ensure that the meters read +0 Vu. For Betacam machines, ensure that the two PB knobs marked "Ch-1" and "Ch-2" pushed in. (Pulled out enables variable output). For the U-matic machine, adjust the two PB knobs (the smaller, protruding knob of the pair) to zero each channel's output.
3. On the audio mixer, set all blue sliders to -infinity (closest to you).
4. Set the MONITOR LEVEL control dial ("Speaker Vol") between 1 and 0 (or else be prepared to have your ears blasted with tone).
5. Move the slider for VTR D up to the 0 (zero) mark. Position this carefully, view the black and white lines from directly overhead.
6. Put the VTR D card online. Press "ON" and "MIX" so that they latch in the depressed (in) position. The "ON" button will illuminate.
7. Ensure that the BAL knob for this input is in the center, at zero.
8. Ensure that the "EQ" button for this input is in the up position.
9. Ensure that the yellow sliders on the master unit are full up at their zero setting.
10. If you hear the 1 kHz test tone, you may reduce the MONITOR LEVEL control further, if it disturbs you. Do not change the blue or yellow sliders!
11. Observe the L and R LED displays on the master unit.
12. If the L and R LED displays illuminate all the green LEDs and just the single orange LED marked zero, the audio levels are calibrated.
13. If not, at the top of the card for VTR D, adjust the red "GAIN" knob until the L and R LED displays on the master unit exactly read zero. This is a very precise analog adjustment; tweek it until the both orange "zero dB" LEDs are illuminated.
14. Eject the test tape, and return the audio mixer to it's normal state.

Cleanup

1. Go to the video switcher's hand-held control unit and press the up arrow. The display should read "BLANKING ON".
2. Press the "HOME" key. The display should start to flash between "SELECT MODE" and "PORT=STATE".
3. Close the silver front cover.
4. Rewind, eject, and store the "Bars & Tone" calibration tapes.
5. Store the green-tip screwdriver back in it's case, and replace the case on the 3rd shelf from the top of the left hand set of shelves behind the preview monitor.
6. Move the M/E Transition level arm to one end of it's range of motion.
7. Press the left-most 6 input buttons marked "BLACK".

Abekas-specific Steps

Detailed setup information about the Abekas is in the Troubleshooting document.