Service manual

Wells-Garnder Color Vector Monitor Guide
Page 43 of 73
THE INPUT PROTECTION CIRCUIT (IPC)
This Modification is for P314 versions of the Deflection Board ONLY. The P327 and P339
versions already have this circuit designed into the board. Here is the text from Atari CO-183-02
(1st printing) that describes a circuit that was sold by Atari to help make the deflection board
more robust. This input protection circuit is unavailable but very simple and easy to recreate
from the schematics provided herein.
New Input Protection Circuit For Wells-Gardner Color X-Y Display
(Supplement to TM-183)
This display contains an additional small printed-circuit board (PCB) that is not described in the
display manual (TM-183). The PCB is mounted in "piggy-back" style on top of the Deflection
PCB.
The input protection board was added to protect the fuses in the display from damaging input
voltage conditions. Without this board, the display fuses might blow in the event of an
intermittent or long-term game PCB failure. With this board, the screen will momentarily go
blank if the average X- or Y-axis voltage(s) exceed a certain level. The screen then automatically
recovers for normal game play and earning when the voltage(s) return to normal.
If this display is used in a Tempest (TM) game, be sure to correctly adjust the X and Y SIZE and
CTR video pots on the Tempest Analog Vector-Generator (main) PCB [see text above]. The
instructions for these adjustments are printed on the Tempest schematics - Sheet 2, Side B - 3rd
printing or later. Improper adjustment may cause the screen to go blank during normal game
play.
Input Protection Circuit (IPC) PCB Parts List
Part No. Description (Reference Designations in parentheses)
24-250107 100 uf Aluminum Elec. Fixed Axial-Lead 25V Capacitor (C1,2)
31-1N914 75V Type-1N914 Switching Diode (CR2-4)
32-1N751A 5.1V 400mW Type-1N751A Zener Diode (CR1)
33-2N3906 PCB Switching and Amplifying Transistor (Q2, 4, 5)
34-2N3904 Type-2N3904 NPN 60V 1-Watt Transistor (Q1, 3)
52-222 22-Gauge Jumper Wire (2 in. required)
110000-223 22K Ohm, +/- 5% 1/4 W Resistor (R1, 8, 11)
110000-273 27K Ohm, +/- 5% 1/4 W Resistor (R5)
110000-393 39K Ohm, +/- 5% 1/4 W Resistor (R4)
110000-682 6.8K Ohm, +/- 5% 1/4 W Resistor (R6, 7)