Wells-Gardner Vector Monitor 6100 Faq And Guide Version

							Wells-Garnder Color Vector Monitor Guide Page 61 of 75 3 - X CHANNEL CURRENT LIMITER 
 
The X channel of this monitor must do more work than the Y channel. This modification limits 
the amount of current that can be delivered to the load and the X channel output transistors are 
moved so they may be more efficiently cooled by convection currents. 
 
A. Remove the plug from J700 and reconnect at J600. The cable of P700 will need to be 
lengthened before this can be done. This move connects the transistors on the bottom 
chassis plate to the Y channel. 
 
B. Transistors mounted on the side of the chassis panel may now be connected to J700. 
These are now the X channel outputs transistors. The side panel allows more air currents 
to pass over the transistors and consequently more efficient cooling. [If this monitor is 
mounted vertically in a Tempest, the Y channel output transistors are already oriented for 
optimum convection cooling and do not need to be moved.] 
 
[notes from Zonn: 
* Moving the transistors seems more like superstition to me.  Aluminum is a better 
conductor of heat than steel, so it could be argued that the X drivers should remain 
where they are since the aluminum can dissipate heat faster than the steel frame. If 
things need cooling, install a fan.] 
 
C. Remove the emitter lead from the transistor sockets on the side and place a 0.2-ohm, 
3-watt resistor in series with emitters of Q705 and Q706 (as in Schematic 3.1). [I believe 
they mean the transistors at physical location Q605 and Q606. If you have just switched 
the X and Y Channels, it would make little sense to make the modifications to the 
transistors driving the Y Channel.] 
 
D. Place two SK3081 diodes in parallel with the base-emitter circuits (Schematic 3.1). 
 
NOTE: When the currents through the emitter resistors reach 3 amps the voltage drop is such 
that the diodes across the base-emitter circuit will start to turn on. This action will drain current 
away from the base circuit and prevent transistors Q705 and Q706 from passing too much 
current. 
 
[notes from Zonn: 
* Limiting the output current on the output transistor may not be a bad idea, if it does 
not slow down drawing speeds enough to affect the display. Though it seems silly just to 
do the X transistors.  During high-speed moves, both X and Y channels will have to pass 
the same amount of current.  While its true that the X channel is larger than the Y, and 
therefore, on the average, will have Longer moves, and therefore possibly get hotter, the 
instantaneous current peaks on both are the same. Since its most likely these peaks that 
would blow the transistors, youd think both X and Y would be protected.] 
 
  
						

							Wells-Garnder Color Vector Monitor Guide Page 62 of 75 4 - HIGH VOLTAGE POWER SUPPLY 
 
These changes to the high power supply should reduce incidence of failure due to high 
temperatures and/or low voltage power supply failures. 
 
A. Replace capacitors C901 and C902 with 220F 50V capacitors. [Original capacitors 
are 100uF 50V.] 
 
B. Replace transistors Q901 and Q902 with transistor type 2N2102. [Originals are 
MPSA06.] Place a heat sink for a T0-39 package on Q901. Take care not to allow the two 
transistors to touch. 
 
C. Replace C905 with a 50uF 200V capacitor. [Original is a 33uF 160V.] 
 
D. Solder an SK3081 diode across capacitors C910 and C905 with the polarity of the 
diodes opposite that of the capacitors. 
 
E. Cut vents into the aluminum cover of the high voltage unit (as illustrated in Figure 
4.2). 
 
 
NOTE: The last procedure is the most important of [the HV] modifications. The vents will allow 
convection currents to cool the high voltage section reducing the thermal stress to these circuits. 
Also, if the power supply modifications are performed, this entire modification becomes 
mandatory. 
 
[notes from Zonn: 
The experiments I did on the high voltage were different than those described. 
 
One thing I noticed about the high voltage sections is that transistor Q900 is dropping 19.6 
volts! Based on a 2.1v drop across R901, Q900 is passing .538 amps, at 19.6 volts thats ~10 
watts. (This could be a bit high since R900 supplies more than just Q900 with current.) 
 
That was quite a bit, and since I did not see anything else that needed the full 25v, except 
for T901, (It looks like they run the output HV transformer with ~30v), I installed a pre-
regulator on the +V side. Since they were using a 13v zener as a voltage reference, I chose a 
15v regulator (7815 or equivalent). 
 
This was a few years ago, but I remember it working pretty well. The heat dissipation on 
Q900 went *way* down (everything ran nice and cool), and I do not remember any adverse 
effects on the HV output (vectors were fine and nice and stable.). With a +15v pre-
regulator, Q901 would only be dropping 6.9v, or less than 4 watts. This also significantly 
drops the current demands on Q901. 
 
I do not currently do this since it was just tacked on. I got really busy at that point and 
never pursued it any further, so I never tested things like the Star Wars explosion, etc. --  
						

							Wells-Garnder Color Vector Monitor Guide Page 63 of 75 mostly just the tempest attract mode. So there could be some unknown problems with this. 
It is also very possible that some other resistor values might need changing in the voltage 
regulator to compensate for the lower input voltage. (Lowering R905, R906 and R913 come 
to mind. And it might be a good idea to re-route R917 to a position in front of the pre-
regulator.) 
 
By dropping the voltage with a pre-regulator you move much of the heat dissipation to the 
regulator and away from the HV regulator. This seems like a good idea and should 
probably be investigated further.] 
 
(Schematic redrafting courtesy of Matt McCullar) 
 
Schematic 1.1   
						

							Wells-Garnder Color Vector Monitor Guide Page 64 of 75  
Schematic 2.1  
 
Schematic 3.1   
						

							Wells-Garnder Color Vector Monitor Guide Page 65 of 75  
Schematic 4.1  
 
Figure 4.2  
  
						

							Wells-Garnder Color Vector Monitor Guide Page 66 of 75 Appendix B:   How To Make A Tempest Monitor Trouble-Free  
 
Here is an article from the April 15, 1983 issue of Play Meter magazine (page 191). The article is 
from a regular feature in the magazine called FRANKS CRANKS by Frank The Crank 
Seninsky. 
 [what does this modification do??? More detail here!] 
 
HOW TO MAKE A TEMPEST MONITOR TROUBLE-FREE. 
 
Ataris Tempest, when it is working, is not a bad game. Its just a shame that the monitors only 
last a few weeks (sometimes only days) between service calls. Most of the time, the monitor sits 
neglected on a techroom shelf. 
 
Atari has developed a monitor protection board [included earlier in this text] to protect the 
monitors components (2N3716 and 2N3792 X OUTput transistors, two each located on 
chassis frame) if and when there is a RAM lock-up on the Tempest CPU board. I want to clarify 
that the Wells-Gardner monitor is not at fault. Also note that on the later Atari games, the 
protection circuit has been incorporated into the board circuitry. [These statements seem to imply 
that this fix is compatible with the Atari upgraded P314s as well as P327s and P339s and will 
provide additional protection; in fact, I have seen it on a P327 before. It is sufficiently ambiguous 
that the exact opposite can be inferred. Judging from the areas of the board it alters, I would say 
it is incompatible (duplicates) the other fixes in this section.] 
 
Its common knowledge that you can purchase a broken Tempest game cheap. With about 20 
minutes of your time and a couple of dollars in parts, it is possible to add just six common 
components to the monitor deflection board and have a Tempest that will stay on location and 
work.  
 
The parts required are: 
· two-1N914 diodes  
· two-1N4737 diodes  
· two-1K OHM 1/4 W resistors  
						

							Wells-Garnder Color Vector Monitor Guide Page 67 of 75  
FIRST HALF 
 
Take the anode ends (the ends opposite from the marked rings) of a 1N914 and a 1N4737, and 
solder them to one end of a 1K-ohm resistor so that it looks like this:  
 
                               ANODE +------+-+ CATHODE 
                            +--------+1N4737| +--------+ GROUND 
CATHODE +-+------+ ANODE   /         +------+-+        | 
--------+ | 1N914+--------+                           ===  C700 
R700    +-+------+         \         +--------+        | 
                            +--------+ 1K ohm +--------+ -27 VOLTS 
                                     +--------+ 
 
Locate C700 in the top left of the monitor deflection board. (See Figure 13 on page 20 of Atari 
TM-183 Wells-Gardner Quadrascan service manual; second printing) and solder the cathode of 
the 1N4737 to the ground side of C700 (right side in Figure 13). Solder the end of the 1K-OHM 
resistor to the -27 volt side (left side) of C700. Solder the one remaining wire (the cathode of 
1N914) to the X INput side of R700 (top end of R700). You are now halfway finished. 
  
HALF TIME 
 
Take a five-minute break; you deserve it. 
  
SECOND HALF 
 
Take the remaining 1N914 and 1N7437, and solder the cathode ends of each diode together with 
one end of the 1K-OHM resistor so it looks like this:  
 
             ANODE +------+-+ CATHODE 
GROUND    +--------+1N4737| +--------+ 
          |        +------+-+         \ CATHODE +-+------+   ANODE 
C701     ===                           +--------+ | 1N914+-------- 
          |        +--------+         /         +-+------+    R700 
+27 VOLTS +--------+ 1K ohm +--------+ 
                   +--------+ 
 
Locate C701 (top middle in Figure 13) and solder the anode of 1N4737 to the ground side of 
C701 (right side). Solder the end of the 1K-OHM resistor to the +27 volt side of C701 (left side). 
Go back to the same X INput side of R700 and solder the remaining wire (the anode of the 
1N914) to this connection. Make sure that you have a good solder connection at the X INput of 
R700 as you now have a three-wire joint. 
  
						

							Wells-Garnder Color Vector Monitor Guide Page 68 of 75  
FINAL TWO-MINUTE WARNING 
 
Make sure that none of the wires of this modification can come into contact with the other board 
components [easy to do; there is a lot of bare PCB in this area; you may want to tape/glue the 
leads down], especially the brown ground wire located to the right of R700. If the modification 
hits this brown wire, you can consider it a fumble and you just blew your lead and the game.  
  
						

							Wells-Garnder Color Vector Monitor Guide Page 69 of 75 Appendix C:  Theory of Operation  
 
THEORY OF OPERATION:  Wells Gardner Quadrascan Color X-Y Monitor 
 
 
CAUTION!!! LETHAL VOLTAGES ARE PRESENT IN THIS MONITOR, IF YOU HAVE ANY DOUBTS ABOUT YOUR ABILITY DO NOT ATTEMPT TO REPAIR YOUR MONITOR!!  
 
The “Quadrascan” color X-Y display was designed and built by Wells Gardner Electronics Corp. 
This display differs VERY LITTLE from the Electrohome G-05 Black and White X-Y monitor. 
The only difference is that this monitor has three Z amplifiers to control three color guns.  Refer 
to the G-05 theory if there is any confusion on operating principles.   
 
 
PINOUTS 
 
Pin Description Notes 1. Red input 4.0V full on; 1.0V black level 2. Green input 4.0V full on; 1.0V black level 3. Blue input 4.0V full on; 1.0 black level 4. Red GND  5. Green GND  6. Blue GND  7. X input 16V P/P  2.5Kohms 8. Y input 12V P/P 2.5Kohms 9. Not Used  10. X GND  11. Y GND  12. Power GND  13. 25VRMS  14. Power GND  15. 25VRMS   
 
LOW VOLTAGE POWER SUPPLY 
 
The input voltage of 48 VAC from the game power supply enters through fuses F100 and F101.  
Diodes D100 through D104 form a rectifier bridge that converts the AC input to an unfiltered  
						

							Wells-Garnder Color Vector Monitor Guide Page 70 of 75 DC (about 35V). Capacitors C100 and C101 form the first stage of filtering.  Resistors R102 and 
R103 and capacitors C102 and C103 form two low-pass filters which help filter out AC ripple.  
Transistors Q100 through Q103 form and active filter that provides the stable, filtered DC 
voltages. 
 
The degaussing coil operates when power is first applied to the display, when the PTP(positive 
temperature coefficient) thermistor is cool. Diodes D106 and D107 form a protective barrier 
from any residual current that might enter the degaussing coil during normal game play. The 
output voltages from the low voltage power supply should be as follows: 
 
J101-2 ground J101-3 +25 volts J101-4 -25 volts  
The picture tube filament voltage is taken from the front end of the low-voltage power supply 
through D108 and R107. 
 
 
X AND Y AMPLIFIERS 
 
Both the X and Y amps are nearly identical. Only the Y amp is described.   
 
The Y deflection signal from the game board is applied to the base circuit of transistor Q600.  
Transistors Q600 and Q601 form a differential amplifier. Transistor Q602 is a constant current 
source providing current to the differential amplifier. Transistor Q603 is the driver transistor that 
provides current to the emitter-follower transistors Q605 and Q606. Transistor Q604 is a 
constant current source that provides current to the driver transistor Q603. Fuse F600 can open in 
case of circuit failure, protecting the deflection coil in the yoke from damage. 
 
 
Z AMPLIFIERS 
 
Since the red, green and blue amplifiers are identical, only the blue amplifier will be described. 
 
Transistor Q502 is a common emitter amplifier used to provide gain for the blue intensity signal. 
Resistor R509 is the blue drive pot, which determines the amount of gain in the blue amplifier. 
Resistor R513 is the blue bias pot, which determines the cut-off characteristics of the blue 
amplifier. The output of the Z amplifiers bias the cathodes of the three electron guns within the 
picture tube. 
 
Transistor Q503 is biased by a voltage from the spot killer. When transistor Q503 is cut off, the 
collector of Q503 rises to the zener voltage of ZD500 (+4.3V). This allows the emitter of 
transistor Q502 to rise in voltage, which disables the color signals to the picture tube.