Service manual

Wells-Garnder Color Vector Monitor Guide
Page 34 of 73
Size and Position
The manuals do not talk much about adjusting the size and positioning of your screen but that is
easy to do. There are small potentiometers on the game board that are clearly labeled which
control X and Y centering as well as X and Y size. There are no positioning or size adjustments
on the monitor itself.
The following adjustments refer to the eight tiny blue and/or black potentiometers found on the
game board. If your lines on the screen are not meeting at the "joints" properly or your text and
numbers are not lined up properly on the statistics screen then you need to make these
adjustments. This information is directly from the Tempest schematic diagram supplements
(sheet 2, side B, 3rd printing) so locations/numbering/labeling of the pots may be different for
other vector games but the instructions should be relatively portable...
All of the following controls exist in the Vector Generator section of the game PCB;
THEY ARE NOT IN THE MONITOR!
+------+ +------+ +------+
|/\/\/\| | | | | | |
|\/\/\/| | | | | | |
|/\/\/\| | | | | | |
|\/\/\/| |--- | |--+---|
|/\/\/\| | -----| | | |
|01..YZ| | | | | | |
|\/\/\/| | | | | | |
+------+ +------+ +------+
screen I screen J screen K
• Enter self-test and advance screens to the diagonal crosshatch pattern [the one with the
line of numbers and letters at the bottom; screen I].
• Adjust "CENTER" pots: Adjust X-CENTER (R147) and Y-CENTER (R167) so that the
pattern is located at the middle of the screen.
• Adjust "SIZE" pots: Adjust X-SIZE (R150) and Y-SIZE (R168) so that the pattern
exactly covers the whole visible screen.
• Adjust the "BIP" pots ["BIP" stands for "Bipolar." The BIP pots provide the offset
current to convert the Unipolar DAC to one that provides a Bipolar output]: Adjust the X-
BIP (R118) and Y-BIP (R117) so that the corners of the diagonal lines rest exactly on the
sides of the outer rectangle. [NOTE: It may be easier to advance to the screen with the
single large cross-hair on it to make the BIP adjustments; just make sure the lines meet at
exactly the center. Using the cross-hair screen, you should try to make screen J look like
screen K. Be careful when joining the lines in the middle that you do not overlap; it is
VERY hard to notice this. You might want to make a big gap (go the wrong way) and
then converge until the two segments just touch. Screens J, and K were added and are not
shown in the original document.]