Subject: How to repair Atari's color XY (vector) monitors (update)
From: [email-masked] (Gregg Woodcock)
Date: Thu, 13 May 1993 15:14:41 GMT
Newsgroups: rec.games.video.arcade

I decided to combine the Ampliphone information and the Wells-Gardner
repair information into one file.  Here is the updated repair text:

This is a tip sheet I originally grabbed off the net from Rick Schieve
about how to fix Atari's color XY (vector) monitors.  I have used the
information to fix 5 Tempests, a Space Duel, and a Star Wars machine
with 100% success rate.  I have added substantially to cover all the
things that I discovered that were not mentioned in the original
article.  All the machines came to me dead and cheap and some of them
have broken more than once since I've had them but I am so good at it
now that I can diagnose and fix a machine in less than 15 minutes.

Vector monitors are available in black and white or color.  A black and
white picture tube has one electron gun that lights just one type of
phosphor (usually, but not always white).  Color tubes have 3 electron
guns that when the yoke and neck magnets are aligned properly, each hit
their own phosphors only, either red, green, or blue (RGB).  Something
called a shadow mask is used so each gun hits only one set of phosphors.
This is just basic TV stuff and holds true for raster monitors too.

The electron guns in the neck of the tube emit a stream of electrons
that bombard the face of the tube that would hit dead center if not for
the deflection magnets on the neck of the tube.  There are two
deflection coils.  One for horizontal deflection (X) and one for
vertical deflection (Y) of the electron beam.  Consider the center of
the screen to be (0,0) volts to the deflection magnets.  If you want to
move the beam to the right you put a positive voltage on the horizontal
deflection "X" coil (+,0).  A negative voltage moves it to the left.  Up
and down are accomplished with positive or negative voltages to the
vertical deflection (Y) coil.

The deflection coils are driven with the same kind of circuitry some
audio amplifiers use.  Imagine that the game puts out pre-amp levels and
that the monitor amplifies and displays the output.

The third section is what (at least by Atari) is called the "Z"
amplifier which controls the brightness.  There is a "Z" amplifier for
each electron gun so that means a black and white vector has only one
"Z" amp while color has three "Z" amps.

So to draw an asteroid the game shuts off the Z amp or amps and applies
the correct vector information to the X and Y amplifiers driving the
deflection coils to move the beam to the desired location.  Then the
appropriate Z amp or amps is turned on to illuminate the screen and the
vectors are modified to draw an outlined asteroid.

On most monitors you can turn the brightness up to the point where the Z
amps don't completely shut down and you can see the full path of the
electron beam as it flys around.  I don't think I care to write the
program that does this in real time!

What I have described so far is basically on the Wells-Gardner or
Electrohome monitors used by Atari and at least in one Midway vector
game (Omega Race).  Stuff deleted...

Knowing how these things work helps greatly in trouble-shooting.  For
instance deflection of the beam to the edges of the screen puts the
greatest strain on the X/Y deflection circuits so if you monitor has
problems at the edges, something is weak.  The monitors make their own
positive and negative DC from AC inputs so a reasonable thing to check
would be the power supplies.

Vector monitors are also fussy about the quality of certain transistors.
The X and Y deflection circuits are very much like audio amplifiers and
tend to be hard on the big transistors used in the final stages of
amplification.  The Atari vectors use a push/pull rearrangement with NPN
and PNP transistors for both the horizontal and vertical amps.  If you
loose one of these transistors you loose deflection in 1 of 4 directions
depending on which transistor goes out.

There is another circuit in the Atari stuff that is very important
called the spot killer.  What the spot killer does is to shut down the Z
amps if the X or Y circuits get bad and the beam won't move around the
screen enough to keep from burning the phosphors.  The phosphors will
become permanently damaged if the beam stays in one place for too long.
When the spot killer is active a red LED on the monitor main
(deflection) board lights.  The spot killer also lights if the logic
board does not supply the low level X and Y signals for the monitor to
amplify.

----------------------

DO NOT TRASH YOUR AMPLIPHONE COLOR XY MONITOR!!!  IT IS REPAIRABLE!!!

Atari games used 2 different (but pinout compatible) versions of the
color XY monitor.  The first and most unreliable was the Wells-Gardner.
The second (found mostly in Star Wars machines) was the Ampliphone.  The
Ampliphone was commissioned as a replacement to the infamous
failure-prone Wells-Gardner.  Unfortunately it had a horrendously
unreliable Acille's heel; the HV flyback transformer.  This part is
widely believed (falsly) to be impossible to replace.  As soon as Atari
heard about all the failures of the flyback, they commissioned a third
party to supply them with a ton of replacement flyback transformers for
the Ampliphone monitors since they are so unreliable.  Unfortunately
(for Atari), by the time they were manufactured, nobody cared anymore
(because the games that used the Ampliphone were getting old and
starting to be retired/converted anyway or else they had Wells-Gardner
retrofits in them) and so this fact is not widely know to most people in
the industry.

The replacement flyback transformer was over spec'd to the max so that
it would not fail as much as the original part and to date Atari reports
that THEY HAVE NOT HAD EVEN ONE REPORT OF THE REPLACEMENT EVER FAILING!
The only catch is that Atari replacement parts are only supplied at the
wholesale level to official Atari game distributors.  To find out the
distributor closest to you so that you can order this part from them,
call Atari at 408/434-3700 and give them you Zip or Area Code and they
will give you a business name and phone number.  I am pretty sure the
suggested retail price is about $160 but that is significantly cheaper
than buying a Wells-Gardner retrofit that you will have to repair about
once a year.

OK, so that was I said before and now I'll talk about specifics and what
devices I often find bad in the Wells-Gardner color vector monitor.  If
you don't have a manual for this monitor, get one, as it does a good job
of explaining how each section works and also how to adjust it.

Some words of caution on the manual.  I've got 2 versions of TM-183 (1st
and 2nd printings both from 1981), but there was a third printing which
shows the redesigned boards that I have never seen (let me know if you
have one).  Neither of the first 2 printings show all the different
versions of this monitor (I don't know exactly what the third printing
shows).  There are 2 design variations for each of the 3 boards and 3
implementations for the deflection board (the largest of the 3).  The
original designs are labeled P31X and the newer, more fault tolerant
designs are labeled P32X.  The deflection boards are P314 and P327 but
314 has 2 (schematically equivalent) varieties:  one all on one board
and one with some of the circuit suspended on a small satellite/daughter
board.  The neck boards are P315 and P328 (328 has a brightness
adjustment in one corner) and the HV power supply boards are P316 and
P329 (329 has an LED, a HV limit pot, and an extra electrolytic
capacitor, C22, which is supposed to be 10uf at 63V).  After much very
disturbing feedback about the performance of the monitors, Atari had all
the boards redesigned to be more robust.  The P32X versions are the
newer versions of the boards.  Here is an Atari Field Service bulletin
courtesy of Al Kossow ([email-masked]) which probably is
describing how to upgrade a 314 to a 327:

================================================================================
Atari Color X-Y Display Deflection PCB

You should do the following modifications to help prevent the Deflection PCB
from failing.

Parts List

6       1N4002 diode
2       1N754A 6.8V Zener diode
2       1N756A 8.2V Zener diode
2       12 ohm 5% 1/4 W resistor

1)      Connect the two 1N754A zener diodes together as shown in Figure 1

        +-+----+     +----+-+
     ---+ |    +-----+    | +-----
        +-+----+     +----+-+      (this was a drawing, but you get the idea..)

2)      Connect the two 1N756A zener diodes together as shown in Figure 1

3)      Remove diode CR2 and solder in a type 1N4002 diode in its place
4)      Remove diode CR11 and solder in a type 1N4002 diode in its place
5       Remove resistor R12 and solder in a 12 ohm 1/4W resistor in its place
6)      Remove resistor R35 and solder in a 12 ohm 1/4W resistor in its place
7)      Find the Y Deflection Circuit (upper left area of the schematic).
        Resistor R1 has two leads to it. Find the lead that goes to the yellow
        wire. Connect this lead to the cathode of one of the 1N754A diodes.
        Connect the cathode of the other type 1N754A diode to ground.

8)      Find resistor R24. It has two leads: one runs to an orange wire.
        Connect this lead to the cathode of one of the type 1N756A diodes.
        Connect the cathode of the other type 1N756A diode to ground.

9)      Find the 2N3792 transistor Q17. You will be installing a type 1N4002
        diode across the transistor's emitter and collector.

10)     Find the 2N3617 transistor Q16. You will be installing a type 1N4002
        diode across the transistor's emitter and collector.

11)     Find the 2N3792 transistor Q7. You will be installing a type 1N4002
        diode across the transistor's emitter and collector. Solder the cathode
        lead of the 1N4002 diode to the emitter, and solder the anode to the
        collector of this transistor.

12)     Find the 2N3716 transistor Q6. You will be installing a type 1N4002
        diode across this transistor's emitter and collector. Solder the cathode
        lead of the 1N4002 diode to the collector and solder the anode to the
        emitter of this transistor

...slightly different numbering, but you get the idea.  Snubbing diodes
across the deflection amps, back to back zeners on the input to ground.

Since I made these mods, I haven't had a deflection amp go out (but I'm
running the game with the back off now, too..)

NOTE:

(CR2/CR11 are D602/D702)
(R12/R35  are R609/R709) on older monitors
================================================================================

The good part of all this is that the 3 basic units, deflection board,
neck board, and HV board are all interchangeable as units and they are
all connectorized.  In other words if you have one working monitor you
can try the boards from your bad monitor (one at a time) even if the
components are not exactly the same.  Also, the most often failing
components are common to the different versions of the boards.

The very first thing you should do is check all the fuses in the machine
with an ohmmeter.  There are 4 on the deflection board and most Atari
machines have 7 more in the power supply at the bottom of the machine (6
in a bay on the left and one under a black cap on the right).

The only other components (besides the tube itself) are the six
transistors mounted to the chassis.  The 3 NPNs are 2N3716s and the 3
PNPs are 2N3792s which are all in the final stages of the deflection
amps or the power supplies.  The deflection amps are like an audio
push-pull amplifier and to power these amps the monitor takes AC in and
produces plus and minus DC voltages.

2N3792 (PNP) can use NTE 285
   Q706  negative X (left)  for horizontal; negative Y (down)  for vertical
   Q606  negative Y (down)  for horizontal; positive X (right) for vertical
   Q103  output negative power supply

2N3716 (NPN) can use NTE 284
   Q705  positive X (right) for horizontal; positive Y (up)    for vertical
   Q605  positive Y (up)    for horizontal; negative X (left)  for vertical
   Q102  output positive power supply

This gives reference frames for when the monitor is mounted horizontally
(for games like Space Duel and Major Havoc) and vertically (for games
like Tempest).

These transistors often go bad and here is a quick lesson on how to
check a transistor with an Ohmmeter.  Unplug the red plugs from the
deflection board to isolate the transistor from the circuit.  From the
bottom the transistor configuration is (Oh boy!  time for a picture!):

               _
              / \
       base- /o o\ -emitter
            |     |
             \   /    the case is the collector
              \_/    

Pretty crude but you get the idea I hope.  Anyway, with your ohmmeter on
a low scale (RX1) there are 6 possible measurements; B to E, B to C,
reverse probes and repeat.  With the probes one way you should get a 10
to 20 ohm reading and when you reverse the probes you should see an open
circuit.  The last 2 reading are C to E and then reverse the probes and
repeat.  These should both be open.  Only 2 of the 6 possible reading
should show resistance.

So what symptoms go with what.  Well if Q705 (X+) goes the top half of
the pictures is gone (actually compressed into a line).  If Q605 goes
(Y+) the right half disappears.  If more than one goes or either of the
power transistors goes (Q103 or Q102) you get no picture as the spot
killer turns on (the LED on the deflection board lights) and shuts down
the electron beam,

Checking these transistors is one of the first things you should do.
Exact replacements are nice but I've substituted others with some
success especially if you put the nonstandard transistors in the place
of Q102 & Q103 as those two are for the + & - power supplies and not as
critical as the ones that drive the deflection coils.

Also, when replacing these transistors, don't forget the little clear
plastic insulator and make sure the socket is centered.  If any part of
the transistor is touching the chassis you are asking for trouble.  Any
place that has transistors should also have some of the special grease
called Silicone Heat Sink Compound which helps transfer the heat from
the transistor to the chassis so the transistors last longer.  Don't be
nervous about remembering the orientation because the pins are off
centered to make the connection somewhat idiot-proof.

On the deflection board, the most common failures are Q100 and Q101 and
when these go they take R100 and R101 (respectively) with them.  These
transistors are part of the + & - power supply circuit and are often bad
with the resistors really burnt.  Even in-circuit and not isolated from
other components you can still get a pretty good idea with an ohmmeter
if the transistors are bad as transistors tend to fail catastrophically.
In other words they usually completely short (0 ohms) or open.  If you
see 0 ohms where there should be an open circuit or 10 to 20 ohms the
transistor is probably shorted.  If you see greater than 10 to 20 ohms
when the reading should be in that range the transistor is probably
open.  When these resistors go, they usually look very black and
charred.  When these transistors go they usually show a crack in the
case if you look closely at it.

Replace the resistors with the same type but it is not uncommon to see
Q100 & Q101 replaced with a larger transistor that will handle more
current.  NTE 287 is a common modern day replacement for MPSA06 (Q100)
and NTE 159 is a common modern day replacement for MPSA56 (Q101).

Once in a while you will see D105 or D104 open or shorted also.

Watch for broken solder joints at the base of the connector pins for all
the major connectors.  You tend to rock the plugs back and forth when
you pull the connectors and this often cracks the solder joints to the
circuit boards.

These are the most common failures with the deflection board.  Usually,
the electrolytic capacitors are still OK (though always be suspicious of
electrolytics drying up and loosing micro Farads) but if the transistors
in the chassis are OK most distorted pictures are due to problems with
this board.

The neck board very seldom has problems.  The few I've seen are from
mishandling where someone has broken some of the pots that control the
RGB drives.  Check the pots if you are missing a color.

Last is the HV supply.  I've worked on lots of these and have only seen
one of the infamous bad HV transformers.  Normally HV failures are due
to a semiconductor or capacitor failure.

Before you work on this beast, discharge the tube as it can really zap
you even when turned off.  Connect a clip lead between the chassis and
the shaft of a long narrow plastic-handled screwdriver.  Work the end of
the screwdriver under the big suction cup on the top of the tube until
you hit metal.  There will often be a snap (from the spark) as the HV
runs at around 20 thousand volts.  Just go slowly and just use one hand.
It won't bite as long as you are careful.  I discharge the tube with my
HV probe so I can watch the voltage go down and the internal resistance
of the probe bleeds the voltage off slowly.  If the snap bothers you,
put a resistor in series with your clip lead to drain off the voltage
more slowly.  If you don't have this equipment available, a 15 to 20
minute wait after unplugging the game should be sufficient for excess
charge to bleed off naturally.

Let's do this one by symptoms.

Spot Killer LED lit and you don't have any display on the screen at all:
Check the fuses first.  If they are OK, then check the 6 transistors
mounted on the side of the casing as described earlier.  If you find at
least 2 of the deflection ones or 1 of the power ones bad, then that is
definitely tripping the spot killer.  If all this is OK then you
probably have a game board problem (particularly if you can't "play" the
game and hear the sounds and see the credit lights blink after you punch
up credits).

No High Voltage (HV), you don't hear the crackling sound when you first
turn the monitor on:  Check the transistors as I described before.  The
ones I've seen fail most often are Q903, Q902, and Q901 though they are
all suspect.  These transistors will usually have cracks in the casing
if they are bad so look closely at them.  If all this stuff is OK, look
at the electrolytic capacitors (they are the big cylindrical tube-like
parts and are usually blue in color) in the circuit.  They come in two
"shapes":

                                     -----
              -----                  |   |
radial-lead --|   |-- and axial-lead |   |
              -----                  -----
                                      | |

These are designed to burst open when they fail due to overburdening
(but they sometimes don't) so as to be obvious to repairpersons.  The
top (for axial leads) or the side (for radial leads) will be open and
some of the "guts" will be hanging out.  When some capacitors go bad,
they sometimes take the final output resistors R901 and/or R907 with
them (but the resistors will look perfectly OK unless you check them
with an ohmmeter).

Low HV:  Most of you don't have a HV probe but the most common symptom
of this in this monitor is the screen looks like you are looking at the
center through a magnifying glass.  I've seen several time where ZD902
(150 volt zener diode) goes bad and the HV drops from 19.5 kilovolts to
around 10 kV.  It's kind of like the electron beam moves slower with
less HV giving the deflection magnets on the yoke more time to deflect
the beam.  A new ZD902 and everything is better.  NTE 51100A is a common
modern day replacement for this part.

The picture seem to shimmer or kind of sparkle, all the lines seem to be
unstable (this rippling is sort of like when you watch TV with a bad
antennae and lines "walk" around on the screen):  Replace all the
electrolytic capacitors in the HV supply.  Make sure the replacements
are rated at as least as many "working volts DC" WVDC and have as least
as many micro-Farads.  It doesn't hurt to replace a 22 uF @ 50 volt
capacitor with a 50 uf @ 100 volts if that is all you have around.  More
is equal or better.  It is best to keep the capacitance the same if you
can.  Also when ordering and replacing these, be aware that they are
polarized and not idiot-proof; be sure to put them in the circuit so
that they are oriented properly.  Also be aware that P329 has an extra
capacitor that may not be shown in your manual; its value is 10uf at 63V.

Display "implodes" during intermission screen between player one and
player two (Tempest machines only):  This is a design fault in the spot
killer circuitry which accidentally kicks in.  You can adjust your game
board and "shrink" the X deflection some and this should go away.  There
are 2 sets of ROMs for this game and the "compact" ROM set (only half
the ROM sockets are used) is slightly different (the intermission screen
has some other stuff on it) and does not experience this difficulty.

Adjustments:  R918 is the HV adjust and my advice is that unless you
have a HV probe, don't mess with it.  If you do set the HV for 19.5 kV.
Some HV supplies have a HV limit pot with an associated LED.  This is
not discussed in the manuals and is not on all HV supplies.  I'm not
sure what to do with this one.  On the outside of the case are focus and
brightness adjustments.  Adjust the focus until the picture is sharp and
adjust the brightness just under the point where the dot in the center
starts to show.  Be careful to not get carried away with the brightness
as you can do permanent damage to the phosphors.

All the above is assuming you just plug the game in and it doesn't work.
If you happen to be playing the game at the time it fails, you have a
little more information to go on.  If you hear a loud bang like a
firecracker, then check the capacitors on the HV board first because they
can be loud when they burst.  If you see a little bit of smoke inside
the cabinet and smell a hint of "electrical smell", then check the fuses
first.  If you see a ton of smoke inside the cabinet, then check the
large transistors first.  If you start losing quadrants of your screen
intermittently than I would advise replacing the corresponding
transistor before it fails because it can take other components (usually
fuses) with it when it goes altogether.  The same advice goes for the
zooming/magnifying effect caused by ZD902.

Now some things besides the monitor itself.  Tempest is harder on this
monitor than the other Atari vectors.  The attract mode that displays
"TEMPEST" (often burned right into the phosphors) really stresses the
monitor.  For Tempest, I like to do what Atari did when they offered the
Major Havoc conversion.  Add a fan to the back door of the game.  I try
to find a small cooling fan that just moves a small amount of air (not
one that howls).  You have to cut a hole in the back door and position
it so it directs air at the deflection board.  I usually connect the
power for the fan to the wires that head up to the fluorescent light and
put a connector in so that you can still remove the back door (with the
fan mounted on it) without it hanging on the wires to the fan.

All of this has assumed that you had a good logic board in the game and
the monitor was receiving the vector info.  If the spot killer stays on
and the monitor seems OK verify the presence of the X and Y signals by
measuring between ground and pin 7 of the big white connector for the X
signal and pin 8 for the Y signal.  This is an AC signal and if either
is missing the spot killer circuit is just doing it's job and saving the
tube's phosphors.

Here are some neat parts places to get the big transistors (and
other things) that I've posted before:

                     2N3716   2N3792

Newark Electronics    $1.55    $1.49
Chicago 1-708-495-7740

Mouser Electronics    $1.59    $2.38
1-800-346-6873

Allied Electronics    $1.43    $1.24
1-800-433-5700

Digi_Key
1-800-344-4539

Mouser also has the coin door "type 47" bulbs.  Here are a few surplus
type places that I've ordered from that have great prices on things like
electrolytic capacitors that will be happy to send you a catalog:

All Electronics 1-818-904-0524

Marlin P. Jones 1-407-848-8236

As far as adjusting purity (red gun hits red phosphors only, green gun
hits green...)  and convergence (red, green, and blue guns hit adjacent
dots to make white instead of separate colors), that is a whole
different subject and the manual does a good job of walking you through
the procedure.  It doesn't talk much about adjusting the positioning and
size 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.

Obviously, there are lots of possible failures with these monitors.  The
ones I have discussed I've seen in quite a few and probably account for
about 95% of the failures I've seen.

Well, if you have read this far you must have found this article
interesting and I hope useful.  I'll be glad to try an answer any
questions.

                Rick Schieve
                [email-masked]
with additions by:
                Gregg Woodcock
                [email-masked]
-- 
THANX...Gregg   day 214.684.7380  night 214.530.2495  TEXAS NOT CANADA!
[email-masked]  [email-masked]  [email-masked]
*CLASSIC VIDEOGAME COLLECTOR BUY/SELL/TRADE PRE-NINTENDO (ARCADE/HOME)*
"If you quote me on this I'll have to deny it; I won't remember because
I have such a bad memory.  Not only that, but my memory is *terrible*."