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Bally & Stern Fuse/Rectifier Board Voltages
NOTICE: For some very important information, please read the Technical Article Notice and Disclaimer, found on our Technical Articles Index page before performing any of the work described below. The information given below assumes you have read the Notice and Disclaimer first.
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This article discusses checking for vital/critical voltages coming off the fuse/rectifier (power supply) board in Bally games 1977-1980 and Stern games 1977-1984. Bally games 1981-1984 are similar but use a slightly different board mounted in the center of the main cabinet.
The fuse/rectifier board is the small board (approx. 6" x 6") that has 6 fuses on it and is wired directly to the main power transformer. This is a good place to start when things don't work- checking for "vital signs"- or basically power supply voltages that the game needs to function.
The fuse/rectifier board in these games is located in the lower right corner of the backbox in Bally games, and in the main cabinet behind the coin box area in Stern games.
Fuses are always quick/easy to check first. Unplug the game so power is not present, then inspect the 6 fuses on the board. If any are visibly bad, remove and replace them. Use correct replacement value fuses- do not over-fuse.
Sometimes a fuse can look "good" but still be open internally. In this case, simply "looking" at the fuses won't help you find a faulty one. It's best to remove each fuse and test with an ohm-meter to ensure that there is continuity through the fuse. If a fuse has no continuity ("open") or has a high resistance value, then it's bad- replace with a new fuse.
Once fuses have all been checked and/or replaced, apply power and turn game on while watching the fuse/rectifier board. If you see any fuses blow (real quick, bright flash), then you've got a short-circuit either on the fuse/rectifier board, or elsewhere in the game, and futher troubleshooting/diagnosis will be needed to isolate the fault.
If you have a game that is blowing one or more fuses when you turn power on, replace the faulty fuse(s) (or install clip-on circuit breakers for testing purposes), then remove connectors J1 and J3 from the bottom of the fuse/rectifier board. J1 is the small 8- or 9-pin connector near the left edge of the board and supplies power to the playfield. J3 is the long 20-pin connector at the bottom/center of the board and supplies power to the backbox. Leave connector J2 plugged in (supplies power to cabinet and brings 117vac power in from line cord to the fuse/rectifier board and transformer).
Make sure fuses are good (or test circuit breakers are installed) and power game on with J1 and J3 removed.
If fuse(s) still blow, then you've got a fault on the fuse/rectifier board that will have to be repaired. Consult the schematic diagram included with your game manual to see what component(s) are in the circuit of the fuse that is blowing, then diagnose and test those components to try to find the culprit.
Common causes of fuses blowing on these boards are:
Note that the game will still boot and run even if you have a bad fuse or fault in the circuit for TP1 (feature lamps), TP2 (score display power), or TP4 (general illumination). Faults in these circuits will not prevent the game from booting-up (however some features may not work such as lights, score displays, or speech in some Stern games).
Critical voltages are TP3 (5vdc regulator supply power), TP5 (solenoid power), and of course line power (117vac) through fuse F6.
If you have determined that there are problems on the board from testing/diagnosing during this step, those problems will have to be remedied before proceeding. See the section below on Replacement Parts to help find any repair parts you may need.
Once fuses have been verified okay and none are blowing when power is turned on (with J1 and J3 connectors still removed from fuse/rectifier board), then you can do some testing of voltages to determine if voltages are present and sufficient to allow the game to boot and run.
Do two tests- one with connectors J1 and J3 removed, then turn power off and plug J1 and J3 back in, power on, and do a second test. Voltages will differ between tests- see table below for details.
When testing for voltages, you will be measuring voltage between each of the 5 test points on the board, and ground. Place your volt-meter's negative (black) lead on a ground point (metal behind or around the fuse/rectifier board or transformer) and use the positive (red) lead to test voltage at the test points.
Your volt-meter should be set for "DC" voltage for these tests, with the exception of TP4 (general illumination lights) when it should be set on "AC" voltage.
Below is a listing of common replacement parts used on the fuse/rectifier board in these games for repairing problems. If you need any other items, use the Search feature at top of this page to search by game name, part description, part #, etc. Or contact us for further info.
Note on bridge rectifier replacement: The small VJ248 type rectifiers used on these old boards are still being made but are not manufactured in the same electronic specs as the originals, so may not perform as well or as long as original parts. If replacing one of these, we recommend using a larger 3504W wire-lead rectifier, and mounting it on the front of the board, rather than the back (legs can be bent to match the pinout on the front of the board). We recommend using an external heat sink on the BR1 (left) rectifier, if you are replacing with the larger 3504W type rectifier. This helps dissipate heat and make this part last longer. For an image of what these larger rectifiers look like when mounted on these boards, see our part # BSPS018, which is an aftermarket replacement board that comes with 3504W rectifiers already installed.