Service manual

Wells-Garnder Color Vector Monitor Guide
Page 35 of 73
• Adjust the "LIN" pots: Adjust the X-LINEAR (R169) and Y-LINEAR (R165) so that the
diagonal lines are straight. Since the "LIN" pots change the size of the displayed picture
on the screen, you may have to readjust the "SIZE" pots in order to get the correct
adjustment.
White Balance Adjustment
(From sections of TM-183)
Here is a summary of the white balance adjustment sections of TM-183. This is paraphrased and
abridged since the information was spread out over many pages. You should make these
adjustments before you adjust the convergence and purity. Do not adjust the white balance in
reverse order because color changes do slightly impact those other adjustments.
1. Flip the test switch inside the coin door on the top near the hinge (some games may have
the self-test switch mounted in a different area such as on a plate near the top of the coin
box). Tempest requires you to rotate the spinner until the prompt reads "Press Fire and
Zap for Self-Test". (Other games may have similar requirements to get to the self-test
screens or they may take you directly to them automatically. Do whatever is required to
enter the self-test screens.)
2. Advance the screens with the slam (a.k.a. "tilt") leaf switch (this is typically inside the
coin door below the lock) until you get to the diagonal crosshatch pattern screen (see
"screen I" in the previous section). For Tempest, this should be the 1st screen.
3. Turn the focus control (one of the two white knobs on the HV unit) until you get the
optimum screen sharpness possible. Your goal is the best character appearance without
appreciable fuzziness.
4. Advance the screens until you get to one showing seven groups of colored bars of various
intensities. For Tempest this should be the 5th screen.
5. Turn all the potentiometers on the neck PCB to the full clockwise position. Turn the
brightness control (the other white knob on the HV unit) so that only five lines are visible
and sixth line is completely invisible. Adjust the red, green, and blue bias potentiometers
(the black ones) until the 5th line from the right is pure white without any hint of color in
it (the 5th line is the dimmest one and color bias abnormalities are most visible at lower
brightness levels; the goal is to get all five lines to be completely white). Adjust the red,
green, and blue drive potentiometers (the white ones) until the first line on the right is
pure white. Repeat the bias adjustment if the fifth line from the right is no longer pure
white.