TECH: System 80 Problems (LONG)
true...@netwalk.com
Hi! I am new to pinball collecting and trying to get my first game, a
Gottlieb System 80 game (Circus) working again. When I got the game, it was
dead except for a few playfield lights that were not controlled by the CPU.
By changing a couple of fuses and cleaning connectors I got it fired up and
working except for some problems described below that I need help in
resolving.
Problem 1 - Trimming Voltages
*****************************
For some reason the voltages coming of the bridge rectifiers are high (15+
volts on the 12V rectifier) and so therefore are the voltages coming off the
power supply board. I used pot #1 on the power supply board to trim back the
+5V ciruit to its nominal value. However, some of the other voltages (+60
vdc, +42 vdc, etc.) remain higher than nominal. The board has "trim pots" for
these and other voltages but I can't figure out how to adjust them. They look
like little rivets without any kind of cut in them to turn by screwdriver.
Any help here appreciated.
Problem 2 - Dead Lamp Sockets
*****************************
When I got the game up with the new fuses and connector cleaning, I thought I
was home free and only had to change a few dead #44's. However, this did not
prove to be the case. Some of the lines going to CPU-controlled bulbs are
stone-cold dead and others have a weak voltage (less than 1 volt) on them.
Others work fine. In all, 17 of these lamps don't work. It is interesting to
note that two types of output transistors are used for the controlled lamps on
this machine, cylindrical ones with "stool feet" and flat ones with "in-line"
feet. In my case, all 17 of the bad lights are powered by the flat
transistors with the in-line feet (MPS-U45). In all but one case, the
associated IC controlling the transistors has some good and some bad lights.
In one case all of the lamps associated with the IC are dead. My guess is
that the problems I am experiencing are caused by bad output transistors
(MPS-45) and that replacing them will solve it. However, I have no test
equipment other than a multi-meter and therefore can't prove the transistors
are bad. Before I buy a bunch of MPS-45's I would like to get some feedback
from others who have fixed System 80 games. Are these transistors usually the
problem or is it something else on the control or driver board? Also, any
advice on where I can get about two dozen MPS-45's cheap would be appreciated.
Wico wants $1.12 each for them.
Problem 3 - Dead Switch
***********************
One of the three switches on the roto target is giving me trouble. I have
tested the switch and it itself is not the problem. However, when it is
closed, the game does not score the hit and no sound is produced. Therefore I
am guessing it must be something on the Control Board. Any advice on fixing
this problem appreciated.
Problem 4 - Extra Ball Doesn't Work
***********************************
After certain items on the playfield are hit, the roto target lights for extra
ball. However, when the target is struck, the "same player shoot again" lights
on both the playfield and the lightbox do not light up and no extra ball is
awarded. Both of the lights are dead with respect to voltage even when pulsed
during the test sequence but my guess is something else is wrong as I would
expect to be awarded the ball even if the lights didn't work. Special works
OK. Any help appreciated.
As you can see, I am experiencing some of the same frustrations as others with
System 80 games. I didn't know these games were "problem children" when I got
the game but I certainly do now. Nevertheless, I am determined to get this
thing working again and I appreciate everyone who had the patience to read
through this lengthy post.
Tony
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c...@provide.net
> true...@netwalk.com wrote:
> Hi! I am new to pinball collecting and trying to get my first game, a
> Gottlieb System 80 game (Circus) working again. When I got the game, it was
> dead except for a few playfield lights that were not controlled by the CPU.
> By changing a couple of fuses and cleaning connectors I got it fired up and
> working except for some problems described below that I need help in
> resolving.
>
> Problem 1 - Trimming Voltages
> *****************************
> For some reason the voltages coming of the bridge rectifiers are high (15+
> volts on the 12V rectifier) and so therefore are the voltages coming off the
> power supply board. I used pot #1 on the power supply board to trim back
the
> +5V ciruit to its nominal value. However, some of the other voltages (+60
> vdc, +42 vdc, etc.) remain higher than nominal. The board has "trim pots"
for
> these and other voltages but I can't figure out how to adjust them. They
look
> like little rivets without any kind of cut in them to turn by screwdriver.
> Any help here appreciated.
i would personally only worry about the +5 (and maybe the +12) voltages.
make sure you measure them AT THE BOARDS right on the chips, and not at \
the power supply! adjust them accordingly.
make sure the lamp sockets are ok too. i replace lamp sockets a lot
on gottliebs that have dim or flickering lights.
anyway, if your DMM has a DIODE test, you can test them transistors!
1. put your meter on diode test.
2. put the black lead on the base (usually center lead) of a transistor.
3. put the red lead on the two others (base, collector) leads (one at
a time) and note the values. they should be in the .4 to .8 range.
if you get nothing, DON'T WORRY YET.
4. SWITCH THE LEADS. put the red lead on the base now. and repeat step 3.
note in one direction you should get "nothing" (that is the meter
should show no value, which is different than it showing a short).
NPN and PNP transistors will give different results in opposite
directions. but basically you should get between .4 and .8 with the
leads in one direction or the other. dead transistors usually short;
a short is shown by the meter going from zero to some value and back
down to zero. if you get this, you have a bad transistor. note the
meter showing no value is not a short.
also compare transistors between each other. for example, if you are
only testing lamp matrix transistors, you should get about the same
value for all of them, in the same direction. if you get an odd-ball
of the group, it's probably bad!
> Problem 3 - Dead Switch
> ***********************
>
> One of the three switches on the roto target is giving me trouble. I have
> tested the switch and it itself is not the problem. However, when it is
> closed, the game does not score the hit and no sound is produced. Therefore
I
> am guessing it must be something on the Control Board. Any advice on fixing
> this problem appreciated.
with older gottliebs i would really suspect dirty switches. if gold
plated, clean with a business card. if not gold plated, clean with
a flexstone file. dirty switches cause lots of problems. i had a
1989 Bone Busters (system 80b) i worked on over the weekend; lots
of stuff didn't work, and it was all contributed to dirty switches.
also the switch matrix could be out. are the switches that don't
work all in the same row or column? you'll need a manual to figure
that out. but if they are, you have a dead transistor or TTL chip in
the switch matrix. the manual should tell you which switch is in
what row or column.
and you know how to test transistors (from the above explaination),
so you can test the switch matrix trans. you can also test the
TTL chips with your multimeter too (TTL chips are the 14, 16 or 18
pin chips that start with "74", "74S", or "74LS" that control the
transistors):
1. put your meter on diode test.
2. put the RED lead on the ground pin of the TTL chip .
3. put the black lead on each pin of the chip (except for the
+5 pin). again, you should between .4 and .8 for each pin.
NOTE: if you get a short this doesn't necessarily mean the TTL
is bad, but i would suspect it. you really need to do this test
with the chip out of the board. with it in the board you can get
some false reading. just had to warn ya...
> Problem 4 - Extra Ball Doesn't Work
> ***********************************
>
> After certain items on the playfield are hit, the roto target lights for
extra
> ball. However, when the target is struck, the "same player shoot again"
lights
> on both the playfield and the lightbox do not light up and no extra ball is
> awarded. Both of the lights are dead with respect to voltage even when
pulsed
> during the test sequence but my guess is something else is wrong as I would
> expect to be awarded the ball even if the lights didn't work. Special works
> OK. Any help appreciated.
>
> As you can see, I am experiencing some of the same frustrations as others
with
> System 80 games. I didn't know these games were "problem children" when I
got
> the game but I certainly do now. Nevertheless, I am determined to get this
> thing working again and I appreciate everyone who had the patience to read
> through this lengthy post.
also you might want to buy the "Black Hole/Haunted House Club of America"
book from Marco. there is TONS of good gottlieb system 80 fix-it stuff
in that book...
Ericselak
Problem #1: No need to worry about the higher than normal voltages. The
voltages will be higher than normal if they are not driving anything. Which
means not under a load. The +5 V adjustment does have a pot. which you have
adjusted. Personally, I set this to 5.15 Volts. The other voltages +60 and
+42 do not have any adjustments. The little rivets you mentioned are meerly
test points. By touching the test point pad, this will give you the voltage
present. If your displays are not illuminated with a score, the voltage will
be higher because the displays are not lit. If the displays are lit-up with a
score and the voltages are a little higher than normal don't worry about it.
The voltages on the power supply board are not exactly perfect.
Problem #2: Usually the MPS-45's are the first to go. Then the IC chip is
usually second to go. Since you have a multimeter testing the transistor can
be done. But before I go on a long way to test them, is the transistor getting
hot to the touch? Also, some lights will not light up during attract mode. I
would check your connectors very carefully. Also, a bus line could be broken,
this is the bare wire that connects to several lamp sockets. Usually held onto
the playfield with staples.
Problem #3 and problem #4: I never messed with roto targets before but if you
have checked the switch and it's ok, check the diode associated with the
switch. These diodes are a small glass looking device grouped together on a
small circuit board, which could be mounted on the underside of the playfield,
or the inside of the cabinet. Check the diode by setting your meter to
resistance. Make sure the game is off. By placing the black lead of your
meter to the (black ring around the device) striped end of the diode and your
red lead to the other side, you should get a low resistance. When you reverse
your leads, red and black, you should get a high resistance. If this is not
the case, the diode is bad and should be replaced. A bad diode can cause good
switches not to score at all. The best way to test the diode is to unsolder
one lead on the diode. This illiminates it from the circuit, and therefore
checking a diode as metioned above will be more accurate.
Good Luck Tony. Eric.