The Trak-Ball and Optical Sensor FAQ V2.0 (8-11-98) by:
Gregg Woodcock <
[email protected]>
Thanks to:
Gary Ransom <
[email protected]>
John Robertson <
[email protected]>
Rick Schieve <
[email protected]>
Ray Ghanbari <
[email protected]>
Patrick Peters <
[email protected]>
There are 3 basic sizes of Trak-Balls; "Mini" (used in games such as
Centipede and in all cocktail cabinets), "Midi" (used in games such as
Marble Madness and Millipede) and "Maxi" (used in games such as Missile
Command and "Xs and Os" Football). They are all the same except for the
varying sizes of the balls and shafts. The Mini and Midi consist of 1
ball, 1 idler shaft, 2 roller shafts, 2 encoder wheels, 2 radial optical
coupler PCBs, and 6 ball-bearing assemblies.
The Maxi is a little different in that the idler shaft is replaced by a
short rod acting as an axel for one ball-bearing assembly (so there is a
total of only 5 for the Maxi ball). The ball rides on top of this
bearing assembly which spins around the rod (which is the opposite of
the other two points of contact where the ball rides on top of the rods
which spin inside the bearing assemblies). Missile Command (and other?)
cocktail and cabaret controllers (even though they are Mini) use this
same no-idler-shaft design. Generally I have found that if the case of
the controller is plastic, it has an idler roller; if it is metal, it
does not.
Also, while electrically compatible, there are more components on the
opto boards for the Maxi balls. The worst is that the idlers and the
bearing assemblies are unique for the Maxi and are hard to come by.
Luckily the shafts are easily machined (Rick Schieve
<
[email protected]> generally has plenty of "home-brew" shafts
available). As far as the bearing assemblies go, you should exchange
the idler bearing assembly with one of the bearing assemblies from one
of the roller shafts. The idler one is always very beat up around the
ball contact area and since the ball does not touch this part at all on
the shafts' bearing assemblies, they are always in perfect shape (and it
doesn't matter if they're not after the swap).
The Mini Trak-Ball is 2-1/4" diameter which is the exact size of a
standard billiard ("pool") ball. Replacing the standard cue ball with
some other ball is simple and amusing (even down right disturbing) to
see. The Midi Trak-Ball is 3" in diameter. The roller and idler shafts
are longer and have a larger diameter in the Midi and those in the Maxi
(at least the rollers) are even more so. In the Maxi, the overall
height of the ball can be adjusted by moving the piece that the idler
bearing assembly is mounted to in or out on the slots the screws go
through. Get the ball as high as you can without binding and the ball
won't be a finger pincher.
The ball rests in the middle of the assembly and theoretically has 3
tangent points of contact; one in the middle of each shaft. As the ball
is rolled the shafts turn the encoder wheels at the appropriate rate.
This rotation is detected by the sensors on the small PCBs and fed back
as pulses to the game board to be converted to object motion on the
screen. The little black box on the PCB contains the emitter/detector
pairs. There are two pairs so that movement can be detected in both
directions depending on which beam changes state and the current state
of the other beam. The holes in the discs let the beam pass through and
get cut off in regular intervals which allows the computer to calculate
how fast the ball is rolling. If there's no change in the status of
either of the beams, the ball is stationary.
__ Key: E - Encoder wheel (screwed on to one end both shafts).
| B - Ball-bearing assembly
D --E-- D - Detector PCB
| |
`-- | B
| \
B \
| \ B' (for Maxi only)
| \
| - \
| Trak- \
| -Ball B
| -
|
|
B |
B------------------B-----E
|
| |
|__D__|
There always seems to be an mixture of dirt, soda and hair inside a
Trak-Ball so clean it out while it is open or it will only make the
situation worse. Clean the ball and the casing itself with soap and
water, and dry. The ball-bearing assemblies also get gummed up and
rusty. Use some sort of degreaser, like Brakleen (which is available at
auto parts stores, for cleaning/degreasing brake parts) to clean out the
bearings. Let them dry completely after cleaning. If the bearings seem
to roll pretty good without binding I don't recommend replacing the
assembly but do always lubricate them by placing two drops of light-duty
oil, such as 3-In-One (R) oil, in each of the six ball-bearing
assemblies.
The thing that REALLY surprised me about Trak-Ball controllers that have
been heavily used (as all arcade game units have) is that the 3 shafts
on which the Trak-Ball sits will gradually wear down and become concave.
They start out like this: But end up like this:
.---------------. .---___ ___---.
-- -- -- ___---___ --
`---------------' `--- ---'
The wear is so perfectly smooth that, without knowing any better, you
might assume that they were manufactured that way. The plastic ball
wears down the metal shafts over time which increases the friction and
the play of the enclosure and causes the ball to bind and/or hop. All
shafts should be perfect cylinders. This way the friction between the
shaft and the ball is optimal (minimal).
Atari suggested in several manuals that if the wear band exceeds 3/8"
along the length of the shaft it should be replaced. If the wear is
acceptable, clean the shafts with fine steel wool, removing all
corrosion (usually found in the worn area). The biggest improvement
always comes from replacing the shafts.
After you get the controller back together it still can be a bit rough
and need to be broken in. You can get a flat rubber disk that attaches
to the end of a drill that's made to attach sand paper to for sanding.
What I do is just use the rubber pad WITHOUT ANY SAND PAPER on a drill
to spin the ball for a while. Move the pad around to turn the the ball
in various directions. This helps smooth out the bearings and also
wears down the new roll pins just a touch for sufficient contact with
the ball.
If you have a Trak-Ball controlled game and plan on keeping it, I
recommend buying a new set of shafts (and ball-bearing assemblies if
necessary). The play improves dramatically when the Trak-Ball is working
well. In fact, buy an extra set as a backup for the future; they are
pretty cheap.
The best prices I have found on bearings and shafts are at Prestige
(formerly known as ANSCOT) who can be reached at 800.456.7277 (or
810.542.5530). Please let me know if better prices are known. I have
heard HAPP is slightly cheaper on the shafts and are also cheaper for
bearings at $3 individually down to $2.25 in larger quantities.
"Midi" Shaft Set: $12.95
"Mini" Shaft Set: $9.95
Bearing Assemblies: $3.99 each
WICO has comparable prices for the same stuff but their prices vary
constantly so you need to keep checking. I know of no place which
carries the Maxi shafts but any of the shafts should be child's play to
make for any metal-worker who can use a lathe. Having them custom made
should not be too expensive (it could very well be cheaper than retail
in any quantity). Every now and then Rick Schieve <
[email protected]>
does exactly that for the Maxi and sells the surplus on the net. You
might want to check with him to see if he has any extras if you need a
set.
Another good place for spare parts is from home Trak-Balls. The Atari
5200 Trak-Ball controller is nearly identical to a the arcade Mini on
the inside and is likely to have almost no wear (i.e. good shafts). It
has different PCBs (one big one so it can't really be used) and employs
the no-idler-shaft design (so there's no idler shaft) but the 2 main
shafts, their wheels and 5 bearing assemblies as well as the ball can
all be harvested. The ColecoVision "Roller Controller" uses identical
parts as those used in Wico brand Trac-Balls with the exception of the
PCBs which are different but could probably be very easily modified to
work in a Wico controller. Wico controllers use the same PCBs as
Atari's did. I believe that many other units also have parts that can
be salvaged but I'm not certain (the only one I have checked was the
2600 compatible "Accuball" and it has nothing reusable). The rule
should be if you see a brand new (older) Trak-Ball controller for a home
system for cheap, buy it and crack it open.
I have a limited number of NOS Atari 5200 Trak-Ball controllers for sale
for $35 shipped. This will get you a NEVER USED replacement for most of
the parts in your mini controller. The best part is you can put your
used up parts in it and sell it on the net to a classic HOME game
collector for at least $10 (of course letting them know it is in poor
condition). The box, manual and mint casing should be worth that much
to them!
Now what about the case where everything looks good and spins good but
the controller still is not working? One thing to check is the
orientation of the connector. It is not keyed and can easily be put on
upside-down. Doing so does not damage anything even if the game has
been turned on so don't worry about that. There is usually a ridge on
the wire-side connector which is intended to face the wall on the
housing of the PCB-side connector and fit into an reversed ridge to grip
the connectors together.
Each Trak-Ball has two PCBs so if one of them is working and the other
isn't check to make sure the one that isn't working is connected like
the one that is. If you can't tell, try it both ways; it won't hurt
anything.
Next check the PCB itself. Many games have two sets of controllers and
this same PCB is also used in many free-spinning (no stop) steering
wheels and on spinners (like in Tempest). For Trak-Balls, generally what
happens is that one axis works (up and down, for example) and the other
(left and right) either doesn't work at all or it reacts as though both
directions are one (rolling either left or right always moves to the
right). If you swap the PCBs in the Trak-Ball and the problem moves to
the other axis then you know the problem is on the PCB.
A quick warning about switching PCBs; the Trak-Balls manufactured by HAPP
are put together slightly different from everybody else's. If you swap
with a HAPP Trak-Ball and yours isn't a HAPP, the directions will be
backwards (up moves down and down moves up). The direction pins are the
two outer ones on the connector so all you need to do if you want to
permanently exchange PCBs with the HAPP is cut and jumper these pins so
that they are swapped.
It is pretty easy to check the sensors if they are not working. The
underside of the PCB has labels to indicate which is the emitter (LED)
and which is the detector (photo transistor).
First check your emitters since they are the easiest. There's 2 great
ways to do this. The best is to get a camcorder and point it at the
emitters. You should see a flashing yellow-white glow since Infra-Red
falls in the recordable/visible spectrum of the camcorder (note that it
is invisible to the naked eye). The next best way is to buy a Radio
Shack "Infrared Sensor" (Cat.No. 276-1099) for about $5. It is about
the size of a standard large "Band-Aid" (tm) with a sensor strip at one
end. You charge the strip by holding it to room light for 10 seconds
(fluorescent light works best). Then hold the strip in front of the IR
emitter as though the strip were a mirror. You should clearly see a
reflection of the IR signal if it is present.
If one or both of them is not glowing then you either don't have power
getting to it or it is bad. If you can't borrow a camcorder or you'd
like to absolutely confirm where the failure is, you can use a meter.
You should have have a 1.5VDC drop across the emitter with the power on.
The drop will be 5V if open (it shouldn't be shorted since that would
cause you to blow fuses and/or your power supply). If the drop is not
1.5VDC then this emitter is bad; if it is 0VDC then your 5VDC power
supply to it is bad.
Next measure the voltage across the photo transistor and you should see
5VDC going to 0VDC (and back to 5VDC) as you SLOWLY turn the shaft with
the power on. If you don't see this (and the emitter you just tested is
OK), then this detector is bad.
If everything looks OK then, obviously, the problem is somewhere else;
perhaps on the game board's switch input buffer. That's a whole
different story and you're on your own there.
Once you have isolated the bad sensor (usually there is only one), you
need to replace it. All 4 sensors are contained in one black box.
Unfortunately, the sensors are permanently attached to this box so the
best you can do is remove it and cut it in half along the canal. Throw
the half with the one bad sensor away (even though the other sensor is
good) and replace both sensors on that side (they are the same type).
Put the other half back in where it was. Go to Radio Shack or any other
halfway decent electronic store and buy virtually any off the shelf
infra-red sensor parts you can find. If there is somebody there who
seems to know something about their parts (yeah, right) tell them you
are repairing a mouse; they use the same exact sensors.
When you put the parts on the board, align them so that the face with
the "dot" is pointing towards the sensor on the other side of the canal.
Be sure to give them the proper height before soldering; you can always
adjust the angle of the beam by bending or twisting the sensor but the
height is set for good once it is soldered. This repaired side of your
PCB will now not have that fancy black cover to keep the sensors aligned
and block out stray light but in a properly secured control panel, this
won't be a problem.
The cheapest place I have found for these sensors is B.G. Micro. They
call the parts "matched pairs" of photo sensors. You get both 1 SEP8526
LED (the red case) and 1 SDP8426 phototransistor (the clear case) for
only 39 cents. You can order by calling 1.800.276.2206.
Here is a very incomplete list of games and the Trak-Balls used in them;
updates and corrections are welcomed):
Maxi
--------------
Football 2 players x2 {Atari '78, BnW}
Football 4 players x4 {Atari '78, BnW}
Missile Command upright x2 {Atari '80}
Super Missile Attack upright x2 {Atari '83ish}
Basketball upright x2 {Atari '78, BnW}
Midi
--------------
Boot Camp x2 {Konami}
Crystal Castles upright x1 {Atari '84, 3D}
Liberator x1 {Atari '84}
Marble Madness {Atari '84} *
Millipede upright x1 {Atari '84} *
Quantum x1 {Atari '83, Vector}
Rampart x3 {Atari '91} *
Track and Field x2 {Konami '83} *
U.S. Classic Golf x1 {Taito}
Mini
--------------
Centipede upright x1 {Atari '81} *
Centipede cocktail x2 {Atari '81} *
Gimme A Break x1 {Sente '85} +
Mini Golf x1 {Sente '85} +
Missile Command cocktail x2 {Atari '80} *
Missile Command cabaret {Atari '80} *
Snake Pit x1 {Sente '84} +
Unknown size (from KLOV)
------------------------
American Horseshoes {Strata '90}
Birdie King II {Monroe '84?}
Bowling Alley {Midway '78, BnW}
Cabal {Fabtek<TAD '88, 2P}
Capcom Bowling {Capcom '88}
Crystal Castles cocktail x2 {Atari '84, 3D}
KickMan {Midway '81}
Millipede cocktail x2 {Atari '84} *
Reactor {Gottlieb '82}
Shuuz {Atari '90}
Slither {GDI}
Tri-Sports {Midway '83}
Wacko {Midway '83}
* Can play with joysticks/buttons
+ Used "Wico" brand Trak-Ball
--
THANX...Gregg day 972.684.7380 night UNLIST/PUBL TEXAS NOT CANADA!
[email protected] or
[email protected]
*CLASSIC VIDEOGAME COLLECTOR BUY/SELL/TRADE NON-COMPUTER (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*."
