Repair Guide BALLY sound board type AS and AS

Transcription

1 Repair Guide BALLY sound board type AS and AS This type of sound board can be found in the following Bally games: Groundshaker, Future Spa, Silverball, Space Invaders, Rolling Stones, Mystic, Viking, Hot Dog, Xenon, Frontier, Skateball, Speakeasy, BMX, Grand Slam, Goldball. On the board we find a pushbutton as usual to launch a self test of the sound board. BUT some games have no code in their specific sound ROM for the self test, so there is no self test available on these boards. The games missing a self test are: Groundshaker, Future Spa, Space invaders, Xenon, Speakeasy. On the other hand the self test is different, in some games it will launch only a single beep, in others the sound is permanently looped. The difference between the -51 and the -56 model is, at a -56 model can be connected to a vocalizer board, the -51 has no possibility to connect such a board. On the -56 are some jumpers to convert the -56 board into a -51 model. (Jumper settings for downgrading are indicated on the schematics.) A -56 type board, at the red arrow in the front the connector for the vocalizer board.

2 Test. It is a test EPROM, which will test the memory chip U10 and the PIA chip U2and of course the CPU chip U or Both can be used, a jumper chooses which one to use. If you have a 6808 you need a external memory chip 6810 if you have a 6802 as CPU the 6810 is not needed, the 6802 has a internal ram portion who take cares of the needed memory space. Also C27 has to be removed if you test the board without a vocalizer board attached. All the notes about the jumpers and C27 can be found in the schematics. Find the schematics in BALLY schematics section. Place the test EPROM into the socket of the sound Rom U4. If the 5 volts tension is applied the test will start immediately. A control LED connected at pin 15 of the CPU chip U3 will blink if the test runs properly. You can check now all outputs of the PIA (6821) U2 they should go up and down from 0 to 5 volts. If ok push the button on the board, this launches the memory test, the blinking of the control LED stops, and if ok the LED will start blinking again after two seconds, if not ok the LED remains in his actual position, that can be a steady off or on, the test will stay running the memory test continuously, what gives us the opportunity to control the signals at the memory chip. Start. All we need is a 5 volts supply, a loudspeaker and the test EPROM. Get the test EPROM image for 2716 and/or It is to burn into a 2716 or a 2732 EPROM both will work with the same jumpers and connections. <s>i put both images here because sometimes it is easier to come by a 2732 than a </s> (Download the images in section Rom/Prom/Eprom other ROMs strikesandspares)

3 Everything connected +5V comes at pin 5 of J1 and the ground at pin 6. De loudspeaker is plugged in at J2. We make a jumper between TP1 and TP2, this because we do not use 12V for the amplifier chip, for test purposes the amplifier chip works loud enough using only 5 volts. We have of course a control LED connected between ground and pin 15 of the CPU (U3). At the right connector J1, the red arrow points to the 6 volt connection, the yellow arrow to the speaker connection, the red wire is the jumper between TP1 and TP2, and above the connected control LED. The jumpers for a -56 board are; B, C, G, E and H. For a -51 board it is B and C. In both cases when using a 6802 CPU chip jumper B changes to position A, and no 6810 (U10) is needed.

4 Control LED The control LED is a normal LED in series with a 470 Ohm resistor, which is used in many applications of this site. To make one, look at the page "Repair of Bally/Stern CPU boards". Control LED Practical When tension is applied the test starts immediately, the control LED starts blinking, we hear also a smooth but fast heartbeat sound from the speaker, meaning the test program runs just fine. Is this not the case, then we look at some basic signals at the CPU U3, to find out why. On pins 2, 3, 4 and 40 we must find +5 volts, and clock signals at pins 37 and 39 at 37 the signal is strong 2.5 volts and at pin volts, when these tensions are ok and the clocks present the CPU should start, if not remove the test EPROM (U4) the PIA (U2) and the memory chip U10. Now look again if the CPU works, you see if there are signals at the address bus pins 9 to 25 ( except pin 21 = ground) find signals between 0,5 and 2 volts, the same on the data bus pins 26 to 33. Two possibilities: If the signals are there, the CPU is ok, or no signals, then replace the CPU. Now, we have the case of a CPU that runs fine stand-alone but with the test EPROM in place the test won t work = the control LED does not blink. We remove again the test EPROM and look at the signals arriving on its socket. The different data and address signals are there? If not bad contact in the socket, look at the selection signals, we need a 0.5 volts signal at pin 19 and a 4,5 volts signal at pin 20.Use a

5 universal voltmeter, a digital test lamp or a scope to control these tensions and signals. Is there a missing signal look at the schematic to see where it comes from, suspect always sockets, if it is a address or data bus signal that is missing, bend up the pin of the CPU where it comes from, if now the bend up pin delivers the signal that means you have a short on that address or data line. You have to look that up.. Normally you did find now the fault and can start controlling the PIA outputs. These will " dance" up and down from 0 to 5 volts.if some are missing the PIA is bad, if all are missing check again the socket connections,all the signals to the PIA included the selection signals are data or address bus signals, as these where already checked and if no outputs at all the PIA is bad. At this point you must have found the fault. Memory test We start the memory test by the pushbutton on the board. The control LED will stop blinking, and restart blinking after about two seconds if all is ok. If not ok, the control LED will stay in its current state, which can be a steady on or off. Anyway the test is continuously checking the memory and allows us to measure the arriving signals at the memory chip U10. On pins 1, 14 and 15 we find ground on pin 24 we have +5 volts. All other pins receive signals between 1.5 and 3 volts. If that is ok, and the test indicates a bad memory, you can be sure the chip is bad. Otherwise, again, suspect the socket. At this point you must have found the fault in the board. Amplifier and sound generator chip. To test the amplifier, we just will inject some noise by putting our finger on C5 and C2, this will result in a good humming in the loudspeaker if ok at C5 the TDA2002 U9 is good if again we hear the humming at C2 the pre-amp U8 LM3900 is good. The humming is louder at C2 and about half that loud at C5.When the board still does not work in the pinball the only thing that rest is the sound generator U1.To test U1 we will need a game sound Rom that supports the self test. Place your Rom if it supports the self test (see above) or this one (Download: Rom/Prom/Eprom -> other ROMs -strikesandspares) that will give a nice sound. Burn it in a Change the test EPROM by the game sound Rom and start, using the pushbutton. You will hear a sound. If not, replace the AY Addendum On the schematic of the -51 board you find a pulsating generator formed around U7. At the bottom of the schematics the "notes" says that this IC is not always mounted on the board. In fact, I have never seen a board with this U7. When you have a board mounted where U7 is mounted, control of this circuit is easy, pulses are to come out continuously of pin3. If not replace the NE555 the rest of the pulse generator being only three resistors and two condensers.