X-Y MONITOR TROUBLESHOOTING
By Jess Askey 3/19/96
****WARNING - DANGEROUS HIGH VOLTAGES ARE PRESENT IN THIS MONITOR. DO NOT
ATTEMPT TO REPAIR YOUR MONITOR IF YOU ARE NOT 100% SURE OF YOUR
ABILITIES TO DO SO. THE AUTHOR OF THIS DOCUMENT ASSUMES NO
RESPONSIBILITIES FOR ANY INJURY OR DEATH. - *****
The first step in fixing any problem is to know what the problem
(or symptom)actually is. This is your best guide to solving the problem and
fixing the monitor.
Does the monitor work at all?
Is the problem in both the X and Y axis?
Is the problem intermittent?
These are some of the questions to ask yourself, knowing exacty what
the problem is can save you lots of time and frustration.
So, now before you move on, read the theory of operation for the monitor
in question from the manual or from the Vector Page. Understand each section
and what its purpose is in the big picture.
I don't know quite how to do this next part so just skip over the part
that do not apply to your situation.
MONITOR DEAD - No noise, no glowing inside the neck of the tube: This is
probably an external problem. I say this because the
filament inside of the neck( which is used to heat up
and exite the free electrons used to create the electron
beam) is powered directly of the 25VAC before the monitor
fuses. Most likely D108 and R107(if it isn't crushed) are
good. So that means you should check your fuses on the
transformer block and replace them, sometimes they just
go!!?? Another thing that causes this problem is burnt
connections at the fuse block, I have seen many transformer
blocks with burnt tabs on the fuses.
Check your slip-on fuse connections and snug them up
with some needle nose pliers, remember to turn off the
BLOWN FUSES - This will cover most everybodys problem since XY's love to
(or missing eat up those 5 and 3 amp Slow-Blow fuses. If a fuse is
quadrants) take it out and make sure that it was a SLOW BLOW fuse.
FAST ACTING fuses will not work and if you put a higher
rating fuse in, it will not protect your monitor. Yes its
true however that if you put in a 30 amp fuse you will be
shown where the problem is by some nice fireworks and
lots of smoke but you don't want to waste a perfectly
Anyway back to the topic, just remember to put in the right
value fuses. QUICK TIP:
Since everything is slow blow, you
can usually see the fuse start to get red hot before it blows.
so if your quick enough on the power switch you can turn off
the game and save a fuse and still know that the monitor still
needs some work!
MOST COMMON PROBLEM: One of the deflection transistors or
power supply regulators has shorted. The best way to check
this is to get yourself a ohmmeter and measure from each
transistor case to the monitor chassis (GND). None of them
should be less than 10,000 ohms. You have to unplug the transistor
connectors to the board (ex..P600,P700,P100 on Well/Gardner) or
you will get false readings. If you find a short from the case to
ground, that transistor is bad, use an exact replacement. When
putting in the new transistor be sure to use the mica insulator and
some heat sink compound. Or for an easier installation use the
silicon type insulators, they don't need heatsink compound.
PREVENTATIVE MAINTENENCE: Moving your deflection and power transistors
off the chassis and on to a large (real) heatsink, will keep
your monitor running cooler and longer. Williams power supply
sinks hold 2 transistors per and are relatively easy to find.
Sega XY monitor use two nice heatsinks mounted together with a
fan blowing straight through for optimum cooling. I sell kits
that are prewired with all 6 transistors and a fan that will
mount nicely anywhere inside the cabinet. E-mail for details!
After you have replaced all the bad transistors check for
shorts again, plug it all back together and try the smoke test.
Watch the fuses so you can turn off power if they start to glow.
Look at the picture and see if your doing okay, if not measure
the transistor cases again for a short and then move on to the
NORMAL MONITOR OPERATION: This is just for reference so you can narrow down your
search for the problem your monitor is having.
SPOT KILLER -This is shown by the red LED on the deflection board. It
Should turn off about 1 second after you turn on the game.
When it is on, the deflection board is not deflecting the
beam to draw anything and the raster is in the center of
the screen. The edgy oscillation sound you hear during
normal operation is the deflection.
HIGH VOLTAGE - It is difficult to tell if you have high voltage or not, you
can't hear the oscillator as in normal raster monitors because
the XY high voltage oscillator is well above hearing range at
30,000 hertz. One way to tell if you have any high voltage
is to turn up the screen brightness control and see if the
picture "glows" or any other bright objects on the screen. Another
way is to touch the screen and feel if there is any static however
you can really zap yourself if it is dry outside. The best way is to
measure the anode voltage with a high voltage probe or measure the '
screen voltage on pin 9 of the picture tube, it should be 544V.
One more way is to look at the spot killer, if the LED is off and
you have no picture, you most likly have no high voltage either.
If you are now certain after all these checks that you have no high voltage
the first thing to do is to see if your high voltage unit is getting
the +28V and -28V it needs to operate correctly. Check on the input plug
for these voltages in reference to ground. If they are there the problem is
either in the High Voltage unit or your picture tube is bad.
If the voltages are not there then your problem is in the power supply
and not the high voltage unit.
If your problem is in the high voltage unit, there are too many possible
components to tell exactly which part is bad. You can generally trace the
problem to a specific area by checking the voltages listed on the schematic
against yours. Generally Capacitors are the culprits in the high voltage
supply but when they go they will ususally take with them a couple transistors
resistors and/or diodes. Cold solder joints also can cause malfunctions
and are very easy to repair, they look like pitted metal with cracks in them,
resolder any that don't look shiny and/or smooth. There aren't that many parts
in a high voltage unit luckily so you can but get well kits that will generally do
the job. Kits will be available through me in a couple of months.
POWER SUPPLY - The XY power supply is very simple. Usually Q102 or Q103 will go after repeated
deflection transistor failures (it stresses them out). Additionally the heat sink
compound will dry out and these babies will start to get really hot. Relocating them
an external heatsink will improve their life drastically. But if your monitor is
already dead then that is just wishful thinking.
The power transistors will rarely short but if they do your monitor will
probably still work, some other section will fail soon since the nice +/-24V is
now somewhere aroun 38V. Check both power transistors as explained in the previous
section and replace any shorted and/or open transistors.
The most common problem in this section is shorted Zener diodes ZD100 or ZD101.
If they are shorted you will not have any output voltage from that half of the supply.
That will sum it all up for now. I will add more to this as I get more time and some feedback. Send me your
problems with the associated solution and I will post them in here. Thanks Good Luck. You can also