Star Tech Journal

STAR*TECH JOURNAL/JANUARY 1983
8
* CMOS CONSTRUCTION AND HANDLING* NAMCO "SHOOT AWAY'' MAINTENANCE
* "FANKY MALLOON BALLOON MACHINE" OPERATION
By Mark "Bear'' Attebery, Vending International Corp., San Juan Capistrano, CA
CMOS Construction and Handling
To Touch ... Or Not To Touch
That is not the question! We all know that TTL/LS integrated circuits
can be touched, soldered with AC soldering irons, shocked with static
electricity, and come out doing fairly well. But what about those stories
we hear about MOS/CMOS ICs? Can you really destroy a MOS/CMOS
IC by touching the leads? By using the wrong iron in soldering? By
leaving it stored with the TTL/LS I Cs? If so, why use MOS/CMOS I Cs
at all? First, let's look at that last question. SSI (Small Scale
Integration) chips such as AND, OR, NANO, and NOR gate logic
chips react about the same, whether they are TTL/LS or MOS/CMOS;
but when you get into LSI (Large Scale Integration) you will see major
differences. CMOS ICs react much faster than the TTL. This means
that in computers you receive the information you are asking for in about
half the time of a TTL system. (Incidentally, strictly TTL systems are
now obsolete.) Also, you can put more functions on a single CMOS IC
chip than a TTL IC chip of the same size, so that is the answer to "why
use them at all."
Now let's look into the other aspects of CMOS ICs. A CMOS
(Complementary MOS) IC chip is made using PMOS and NMOS
transistors. MOS stands for Metal Oxide Silicon, and the P and N stand
for Positive and Negative ( of course, you say!) channel MOS transistors.
An NMOS transistor looks like this:
VDD+
1. Aluminum
2. SLO 2
3. Silicon
(My thanks to Radio Shack for this illustration!)
A PMOS is exactly the same except the P and N areas are reversed.
The SLOi (silicon dioxide) layer is a glassy film that separates the
aluminum and silicon sections of the chip. This film is the reason
MOS/CMOS I Cs use practically no current, and places very little load
on the source of an input signal. Since the SLOi is so thin a film, it is
easily punctured by static electricity or AC signals, such as an AC
soldering iron. When a CMOS IC is damaged, this is what happens:
Hole
Do's and Don't's for CMOS:
Never store MOS/CMOS ICs in non-conductive plastic, white foam,
"plastisnow" bags or trays. Always use conductive foam; conductive
"slido" containers, or place the I Cs pin down on aluminum foil when not
in a circuit. Never use AC soldering irons. Always use a DC soldering
station, or a battery-powered (rechargeable) soldering iron.
MOS/CMOS chips not only contain more functions per chip, but
they are not limited to the+ 3.8vdc to 6.8vdc power supply that TTL/LS
is. MOS/CMOS voltage range extends from +3vdc to +16vdc. This
means that most chips can be used with TTL systems - in fact, look at
some of your video games and you will see those familiar 7404s and
74163s- but then you will say"Hmmrn, I can't find across in my TTL
data book for this MC 14528BCD". That is because it is a 4528 CMOS
multi-vibrator. In CMO.S all unused inputs must be connected to VDD
( +) or VSS ( Gnd). If this isn't done, erratic chip behavior and excessive
current use will occur. CMOS may be new to you, but it is easy to learn.
We will cover more on CMOS next month.
Namco "Shoot Away" Maintenance
Now let's look at a couple of arcade units we are all familiar with. First,
"Shoot A way" by Namco. The following data is provided by Namco of
America. My thanks and appreciation.
Continued on next page.
Figure 1
Gun Harness Procedure
HEX BOLT
(M5 X 40)
GUN STOCK
...
BARREL
SHOULDER BUTT
,
GUN CORD
YEL
BLU
ORG
CAP BOLT
\ - (M3 X 12)
2 EA