Service manual

Wells-Garnder Color Vector Monitor Guide
Page 5 of 73
meant to keep your picture tube and other components (such as the high voltage transformer)
from being destroyed in the event of a failure involving very large high-voltages.
A detailed Theory of Operation for the Wells-Gardner 19K6100 monitor is included here in
Appendix C.
How Do Wells-Gardner and Amplifone Differ?
While this document will deal specifically with the Wells-Gardner 19K6100, it is important to
note that Atari used two different (but pinout compatible) versions of the color vector monitor.
The first and most common (but also the most unreliable) was the Wells-Gardner 19K6100
which was used in Tempest, Space Duel, and most Gravitars, Black Widows, and Major Havoc
conversions. The second color vector monitor that Atari used was the Amplifone, which was
used in Quantum, Star Wars and dedicated Major Havocs. The Amplifone monitor was also
incorporated into a small number of Gravitar and Black Widow games. The Amplifone monitor
was designed by Atari as a replacement for the Wells-Gardner 6100 to add (a) more reliability
and (b) faster drawing speed.
Each monitor design has a slightly different electrical characteristic and tube shape that will
cause games designed for use with the Amplifone to bulge out around the edges (a defect known
as "barreling") when using a Wells-Gardner 6100 and similarly will cause games designed for
use with the Wells-Gardner monitor to cleave inward around the outer edges (a defect known as
"pincushioning") when using an Amplifone. This effect is quite minor and is really only
noticeable when viewing the self-test screen as this draws a (perfectly straight) bounding box
around the edge of the display. All game PCBs designed to work with an Amplifone monitor
(i.e., Quantum, Star Wars and Major Havoc) do not have the pincushioning correction circuitry.
CRT Monitor Tubes
Here is the complete pinout of both the Wells-Gardner and Amplifone neck/tube.
1. G3 (focus grid)
2. not used
3. not used
4. not used
5. G1 (control grid)
6. G (green cathode)
7. G2 (screen grid; brightness)
8. R (red cathode)
9. H (heater)
10. H (heater)
11. B (blue cathode)