Wells-Gardner Vector Monitor 6100 Faq And Guide Version

							Wells-Garnder Color Vector Monitor Guide Page 71 of 75 SPOT KILLER 
 
The purpose of the spot killer is to turn off the video intensity amplifiers when deflection is not 
occurring. Failure of the spot killer can cause the phosphor coating on the picture tube to become 
burned. 
 
The two signal input voltages to the spot killer are taken from resistors R610 and R710 in the X 
and Y deflection circuits. Diodes D801 through D804 and Capacitors C800 through C803 form 
two separate voltage doublers. The output of the voltage doublers are applied to the bases of 
transistors Q801 and Q802. 
 
When either of the deflection amplifiers is not driving current through the deflection coils, and 
then either transistor Q801 or Q802 becomes biased so that it conducts, which turns on transistor 
Q800 and the LED D800 in its collector circuit. When transistor Q800 is conducting, then 
transistor Q503 in the neck PCB is cut off, forcing the red, green and blue amplifiers to turn off 
their electron beams. 
 
 
HIGH VOLTAGE POWER SUPPLY 
 
Integrated circuit IC901 is a timer circuit that produces a 20 KHz output, which drives transistors 
Q904 and Q905. These transistors are current amplifiers that drive the primary winding of the 
Step down transformer T901. The output of T901 is used to turn on the main driver transistor 
Q906 that in turn drives the High Voltage Step-up transformer T900. The output of the 
secondary winding is applied to the picture tube at the focus and intensity grids and the 19.5KV 
anode. 
 
Diode D901 allows capacitor C910 to charge to +180V during the discharge of the primary’s 
magnetic field. Transistors Q900 through Q903 are error amplifiers that regulate the +180V 
video B+.  Pot R918 provides an adjustment to the video B+ and hence the high voltage. To 
adjust the high voltage, you will need a high voltage probe, a voltmeter, and an insulated 
screwdriver tipped adjustment tool. Turn off power to the display. Connect the high-voltage 
probe to the voltmeter, and insert the tip of the probe under the high voltage anode rubber shield. 
 
Insert the insulated screwdriver tipped adjustment tool through the top of the high voltage cage, 
making contact with potentiometer R918. Turn on the display and adjust the high voltage to 
19.5KV. 
 
  
						

							Wells-Garnder Color Vector Monitor Guide Page 72 of 75 Appendix D:  Common Ground Connections  
 
 
From: John Robertson  
Newsgroups: rec.games.video.arcade.collecting 
Subject: TechTIP: How to make VECTOR MONITORS very RELIABLE! 
Date: 22 Oct 2001 
 
 
It’s been a little while since my last Tech Tip, but this is something that’s been on my mind for a 
while now, and a posting in the Vector mail-list got the following response from me...: 
 
Vector monitors blow up because the ground reference for the monitor drifts relative to the logic 
boards (MPU and video) when the power supply connections overheat. This will then bias the 
input signals offset enough to overdrive the outputs. Hence my argument for chucking the 
original power supply and putting in a switching supply.  I started doing that about ten years ago 
and have not lost a single Electrohome/Sega monitor since. I assume this also kills Tempest/Star 
Wars/Major Havoc/... monitors etc. Those pesky grounds get a few ohms resistance and all sorts 
of nasty things happen.  
 
I first discovered this on Gottlieb pinballs over ten years ago-the ground for the regulator would 
overheat the pin/wiper contact which would become a small resistor and thus the ground of the 
MPU would drift up relative to the cabinet ground, which also happened to be the ground path 
for the driver transistors. When the MPU ground would change to about 0.5 to 0.7VDC above 
cabinet ground the base of the transistors would then start to conduct as the MPU would be 
trying to turn off the transistors, but the Emitters are tied to the cabinet ground. Hence the 
transistors would start to conduct... You will recall that transistors generate far more heat when 
they are used at the beginning of their working range rather when they are switched completely 
on and off as in regular vector monitors (or solenoid drivers, etc.). So in a little while, it croaks. 
No obvious cause...replace the transistors and everything works. For now... 
 
So get VERY GOOD GROUND (COMMON) CONNECTIONS BETWEEN THE MONITOR, 
MPU AND POWER SUPPLY for reliability!!!!!!!!!!!!!!!!!!!!!!!! Solder fat conductors with 
nasty heavy gauge connectors between each component in the system.  Put in healthy 
SWITCHING SUPPLIES! 
 
Happy vectors will result. 
 
John :-#)# 
 
  
						

							Wells-Garnder Color Vector Monitor Guide Page 73 of 75 Appendix E:  Vector Monitor Slew Rates  
 
Vector Monitor Slew Rates 
Courtesy of Jon Raiford 
 
Here is a table of Vector Monitor Slew Rates. Slew rate is a measure of the maximum rate-of-
change of the voltage output.  Put into context, a slew rate is the measure of how fast the 
deflection amplifier can make FULL-SCALE transitions, driving the CRT beam around the 
screen. As the slew rate increases, more objects can be drawn on-screen at the same time and the 
amount of flicker is reduced. If a monitor is not listed, we do not have any available data on its 
speed. 
 
 6400 X 6400 Y Amp X Amp Y 6100 X 6100 Y 19V2000 G05 .5 6us 6us ? ? 10us 13us 4us 5us 1.0 8us 8us ? ? 20us 27us 8us 10us 2.0 16us 21us ? ? 40us 53us 16us 20us 4.0 30us 42us ? ? 80us 106us 32us 40us 8.0 62us 94us ? ? 160us 213us 64us 80us 10.5 84us 131us ? ? 210us 279us 84us 105us 14.5 110us 179us ? ? 290us 385us 120us 150us .05 inches per usec 0.1325 0.08   
0.05 0.0375 0.12 0.0975  
 
The X-axis is obviously the Monitor, the Y-axis is the amount of deflection, and the value is the 
time in microseconds to deflect that far. The last row is the number of 0.05 inches per 
microsecond. 
  
						

							Wells-Garnder Color Vector Monitor Guide Page 74 of 75 Appendix F:  Testing Transistors  
 
Most of the failures in the Wells-Gardner 6100 monitor (as is the case with most electronic 
devices) are semiconductor failures, specifically, the transistors. All transistors discussed in this 
document can be tested in the same way; it does not matter if they are the large chassis-mounted 
transistors or the tiny PCB-mounted transistors. With the transistors out of circuit, set your multi-
meter on Rx1K scale and use the following procedures. 
 
NOTE: ANALOG AND DIGITAL MULTI-METERS REQUIRE DIFFERENT TESTING 
PROCEDURES FOR TRANSISTORS! Digital meters always show infinite resistance for all 6 
combinations (if you accidentally get your skin involved it will show something around 2M 
Ohms). The best way to test transistors with a DMM is to make use of the diode test function, 
which will be described after the analog test. For both methods, if you read a short circuit (0 
Ohms or voltage drop of 0) or the transistor fails any of the readings, it is bad and must be 
replaced. 
 
Why do Digital Voltmeters read open circuits on diodes and transistors? 
 
Because of the ability to use amplifiers, DVM can use much smaller voltages to check resistance. 
For the most part this is a good thing. It allows you to check resistors in circuit, without turning 
on things, like transistors. 
 
Diode junctions (which there are two of in a transistor) do not “turn on” until they reach 
somewhere around 0.4 ~ 0.7 volts, depending upon what they are made of, and a lot of other 
stuff. In a way, diode junctions are similar to neon light bulbs, they act like open circuits until the 
right voltage is reached, and then they act like shorts, until the voltage drops below the critical 
threshold. Without proper current limiting, the diode junctions explode. The thing about diodes is 
that they only do this in one direction, if you switch the test leads, they do not conduct at all.  
(Well, until the voltage gets much higher, and then it is a bad thing. ;^) 
 
Sometimes you want to be able to “turn on” the diode junctions (to test them), so DVMs have a 
“Diode” test mode.  This places enough voltage on the test leads to turn on the diode junction.  
The number you read on most meters is the actual turn on voltage threshold across the diode. 
  
TESTING TRANSISTORS WITH AN ANALOG OHMMETER 
 
For type NPN transistors, lead A is black and lead B is red; for type PNP transistors, lead 
A is red and lead B is black (NOTE: this is the standard polarity for resistance but many 
multi-meters have the colors reversed; if the readings do not jive this way, switch the leads and 
try it again). Start with lead A of your multi-meter on the base and lead B on the emitter. 
You should get a reading of 2.5K Ohms. Now move lead B to the collector. You should get the 
same reading. Now try the other 4 combinations and you should get a reading of infinite Ohms 
(open circuit). If any of these resistances is wrong, replace the transistor. Only 2 of the 6 possible  
						

							Wells-Garnder Color Vector Monitor Guide Page 75 of 75 combinations should show a resistance and that value should be 2.5K Ohms; none of the 
resistances should be 0 Ohms (shorted). 
  
TESTING TRANSISTORS WITH A DIGITAL MULTI-METER 
 
Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect 
the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP 
voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN. Leave the red meter 
lead on the base and move the black lead to the collector. The reading should be the same as the 
previous test. Reverse the meter leads in your hands and repeat the test. This time, connect the 
black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good 
PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN 
transistor will read OPEN. Leave the black meter lead on the base and move the red lead to the 
collector. The reading should be the same as the previous test. Place one meter lead on the 
collector, the other on the emitter. The meter should read OPEN. Reverse your meter leads. The 
meter should read OPEN. This is the same for both NPN and PNP transistors. Thanks to Randy 
Fromm  for this excellent summary of the diode test method. 
 
END