Ok,Those measurements are correct and BR1 is working proberly.
So turn the game on, set your DMM (digitial multi meter) to AC voltage, put the black lead on ground, and check for AC voltage on either side of fuse f114. You should get about 7 volts AC. This means the fuse is good. Now set your DMM to DC volts, and check for voltage at TP8 (test point 8, located at the right side of the driver board.) There you should see about 18 volts. If these things check out, the bridge BR1 is good. No voltage at TP8? That means BR1 is open. For our repair, TP8 does indeed show about 18 volts, so we know things to this point are OK.
If you follow the schematic along past TP8 (where we know there is voltage), you come across a pair of 1n4004 diodes. We can use our DMM and check voltage on the right banded side of diode D2 (see the video). And sure enough, we get about 17 volts (because these two diodes D1 and D2 drop the voltage about 1/2 volt each, from 18 volts to 17 volts.) Now if we check for voltage at f115 (or TP3), we should see 12 volts. In our case we do not. That means that our problem as to be betwen fuse f115 and diode D2.
So what’s left in the schematic? Well frankly not much! Basically LM7812 and two capacitors. The LM7812 is a voltage regulator, takes the unregulated 17 volts and makes it regulated 12 volts (for the switch matrix.) I don’t think I’ve ever seen one of these fail! But the one thing that does fail in this circuit is what’s shown in the schematic below with the red arrow, a 100 mfd 25 volt capacitor C2. It’s not so much that the cap is no longer working, but what it does as it fails. It leaks it’s electrolyte fluids, which eat the circuit board traces (a lot like battery corrosion), and the circuit goes open. Now there’s no 12 volts, no switch matrix, and you get the “check fuses f114 and f115” error message at game boot up.
the LM7812 voltage regulator is right by fuse f115, and the capacitor C2 is just to the left of the LM7812. If you look at the board, nothing visually seems problematic, as the picture below shows. But don’t be fooled by this
Removing capacitor C2 from the driver board shows that there is indeed a problem. The bottom of the capacitor is physically wet and gross, and the driver board where the cap mounts is discolored.
remember, the game thinks that fuse f114 and/or f115 are a potential issue. These fuses, and this circuit, power the game’s switch matrix. And in the switch matrix, there is one switch (usually switch 24) that is permanently wired closed. That is, the cabling going from the CPU board to the coin door interface board (mounted by the tilt bob) has this switch permanently wired closed.
info was gathered from clay's pinballninja site..great site join up over 800 documented fixes from every game..bally/williams,gottilieb,stern,sega,data east and many more just email clay at [email protected]
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Étalle
Detroit, MI
