Circuitry Stupidity

tomdotcom

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What is this symbol?

Ya probably a dumb question haha. But I'm trying to learn how to read pinball schematics/circuits. Trying to diagnose a flasher problem at the moment. Thanks guys.

Edit** For bonus points please explain the flow of the circuit a little bit in easy to understand words :) Maybe it will help more people than just me. Even if they don't admit it :p
 

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That's a light bulb, or flashlamp.

AC Power comes into the board at connector J102. There it is converted to DC by BR4 and smoothed, or filtered, by the 15000uf cap. Power is then sent out to lamp at J107.

It's constant power to the lamp, the lamp is turned on and off by controlling the ground.

The Lamps gets a ground via the TIP102. The TIP102 is turned on and off by the 2N5401, which is turned on and off by the LS374. The LS374 is controlled by the CPU via assorted logic not shown in this diagram.


D
 
Thank d zoot. I thought that was the a bulb symbol but wasn't sure. I have printed myself out a series of tests to do on the br4 bridge, capictor, transistor, diode, etc. Wish me luck haha.
 
If my fuse f111 (secondary flash) is blowing on startup instantly.. can I still test if voltage is getting to the flashlamps or not?

My flashers stopped working on the playfield and in the backbox on my World Cup Soccer 94. I'm trying to decipher if it's a short somewhere in the wiring to the flashers (or a shorted lamp socket) or if it's a problem with the board ie:bridge, resistor, transistor, etc..

Any (testing/fixing) advice will be gladly taken :)
 
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I've narrowed down the connectors on the board. But I'm not 100
percent sure which one(s) to unplug and in what order.

j106 is +20v to insert flashlamps
j107 is +20v to playfield flashlamps

j124/j125 insert flashers
j122/j126 playfield flashers

BR4 is the related bridge.
C11 is the capacitor

Flashlamp circuit j102-f111-br4-j107-j125-j113
 
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Back to the basement. A reply from the legendary Lloyd :)

Lloyd Olson

"Don't worry about unplugging the wrong thing. Just get them back in the
right spots and facing the right way.

With them unplugged and the fuse blows, yes it's a board problem. ( usually
the bridge rectifier, easy to check with a meter and compare to the others
on the board and look for a dead short between the four legs.

If not a board problem, you can put the connectors back on one at a time
until the fuse blows, then at least you narrow your search/work to one line.

Plug in any order you like. Just keep adding them until one pops the fuse.

Don't worry about being new. Look at how much you learned already. LTG :) "
 
Ok I disconnected all 6 connectors. (106,107,122,124,125,126)

The fuse is still blowing even with those connectors pulled off. So I
must have a board problem.

I'm going to try and test the Bridge (BR4). Anything else I can test?

Should I test all the related transistors as well. (I have the flasher
table handy so I know which ones) Q42,Q40,Q38,Q36,Q20,Q22,Q24,Q26

What about any capacitors or resistors involved? Can't see which ones
relate in my schematic :/ c11 is the capacitor maybe?
 
Ok I hooked all the connectors up and tested the Bridge BR4 as per these instructions. I got a value of 0.20 when on the 20 volt setting. So is my bridge bad then?

Testing a Bridge (WPC-S and prior), Under Minor Load, In the Game.
This tip is from John Robertson. This test is a more conclusive way to test a bridge (though a bridge that tests good here can still cause game resets!) This procedure requires a DMM, two alligator jumper wires, and a 6 amp rectifying diode (6A50 or 6A2 or 6A4, or whatever is available; Radio Shack sells 6A50 diodes, part number 276-1661). Here is the procedure:
1. With the game off, clip one end of an alligator test wire on the "+" lead of bridge BR2 (top most bridge) on the driver board. The "+" lead is the top left most lead (see picture below). Often the side of the bridge is labeled too. One lead is "AC", and the other is "+" (connect the alligator clip to the "+" lead, which is the left lead as facing the board).
2. Connect the other end of the alligator test wire on the RED lead of the DMM.
3. Put the BLACK lead of the DMM on the braided metal grounding strap at the bottom of the backbox.
4. Turn the DMM on, and set it to DC Volts (20 volt range).
5. Turn the game on. A value of 12 to 13 volts should be shown. Any less than 12 volts, and the bridge (or the connection to the bridge) is bad.
 
Wow I talk to myself to much evidently haha. Here's a different way to test the bridge that I'm going to try. This could help some pinball newb like myself someday I guess.

A bridge has four terminals: two AC terminals, and two DC terminals
(postive and negative). On the side of each bridge, printed on the
metal casing, there will be two labels: "AC" and "+". From the solder
side of the driver board, mark with a Sharpie pen these two terminals.
Figuring out the other two terminals is easy: the other AC terminal is
diagonal to the labeled AC lead. The negative DC lead is diagonal to
the labeled positive DC lead. Mark these right on the board with the
Sharpie pen. To double check, the two DC leads (positive and negative)
connect to that bridge's respective electrolytic capacitor, and it's
positive and negative leads. Testing a bridge while soldered in the
board (in curcuit) may not give the following results. For example,
testing BR2 in curcuit will not give these results (but most of the
other bridges will). To test the bridge:

1. Put the DMM on diode setting.
2. Put the black lead of the DMM on the "+" (positive) terminal of
the bridge.
3. Put the red lead of the DMM on either AC bridge terminal.
Between .4 and .6 volts should be seen. Switch the red DMM lead to the
other AC bridge terminal, and again .4 to .6 volts should be seen.
4. Put the red lead of the DMM on the "-" (negative) terminal of
the bridge.
5. Put the black lead of the DMM on either AC bridge terminal.
Between .4 and .6 volts should be seen. Switch the black DMM lead to
the other AC bridge terminal, and again .4 to .6 volts should be
seen.

If values outside of .4 to .6 volts are shown for any of the above
tests, the bridge is bad. Typically you will get a zero value (a
short) for at least one of the above tests in a bad bridge.
 
Haha just talking my way through it. Sharing my pinball woes with the masses :) Going to replace the bridge. I'll report back when that's done. I don't have any though, my buddy Dave on here is going to order me some with his order.
 
Got the BR4 bridge replaced. Put the board back in and no go. Still don't have any flashers. The fuse doesn't seem to be blowing anymore. Not sure if that's a good or a bad sign though haha. Any other suggestions?
 
When looking at that circuit you can see that the only things that could cause the fuse to blow would be a shorted bridge rectifier, shorted filter cap, or a short on the power side of the bulb socket/wiring.

If the transistor was shorted it would only cause the light to be on all the time since the light bulb's resistance would limit the current flowing through the circuit. Same thing if the transistor side of the bulb socket was shorted.

Think about the current paths and it'll help you narrow down where the shorts of the fuse blowing magnitude could realistically be.
 
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