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Produkte -> LEON: Sound System 9

WILLIAMS System 9 - Testing the sound section

The sound section on the CPU board contains a separate MC6808 CPU chip (U11), a 6821 PIA (U13), a 6810 memory chip (U12), the sound eprom (27128) at U49, the amplifier is a TDA2002 at U47 and the D/A converter MC1408 at U48. Please note: if a CPU 6802 was used there is no 6810 required. We use a TEST ROM. The checksum of the TEST ROM is [FC3E]. You can use this TEST ROM also to test the sound section on a Williams type 11 CPU board (see the pages for Williams System 11 repairs.)

Running the test:
To test this circuitry we place the TEST ROM in U49. Before powering the board, place back the normal GAME ROM to U20 to avoid conflicts with the running test program. After power up, check at pin 15 of U11 if the test is running. The signal there is constantly flipping from 0 to 5 volts. If not, the program is not running. On the CPU chip at U11 check the basic signals like CLOCK and RESET. These are the same as the ones at the "game" CPU. So, if the game is running, these signals should be ok.

Now, we suppose the program is running, test the output pins 10 to 17 of the PIA at U13 (6821). They have to toggle between 0 and 5 volts. Pins 2 to 9 will not move, they are hold at 0 volt by a direct connection to the outputs of PIA U4. If the pins 10 to 17 do not move, first check the selection signal of the PIA (U13) at pin 23, we need pulses there. If ok change the PIA. If not, check the selection chip at U55 (74LS139). Pins 1, 2, 3 and 4 are inputs and all should pulse. The output is at pin 14. Only pin 14 can be at 0 volt, all others have to be a steady +5. If there is another pin coming to 0 volt the input is bad. If all stay at 0 or 5 volt the chip is bad. (Note from Leons phrases in cursive are not correct for games using speech.)

I assume your PIA is working fine now. We now can proceed to check the amplifier and D/A circuitry.

To produce some sound we need +12 and -12 volts. Use an old PC POWER UNIT for the required tensions +5 volts, +12 volts and -12 volts.


The following connections are needed:

When connecting +12 volts, always remove the jumper eventually set previously to connect +5 volts to Z1.

At power up you will hear a rapid heart-beat sound, showing the transition from +5 to 0 volts. If not, first check the amplifier. Touch with your finger pin 2 of 1J16. A loud hum should be the result. If no sound, replace the amplifier TDA2002 at U47. If the amplifier is ok and still no sound, replace the D/A converter MC1408 at U48.

Testing the sound memory at U12:
Push the SW2 button once (SW2, near 1J16). The outputs of the PIA come to a halt and the sound will stop for a very short while. If the sound restarts the memory is ok. If the sound does not restart the test is running continuously on the memory test. Check the signals to the memory chip. If the signals are ok, replace the 6810 memory chip at U12.

(Text from Leon Borré, slightly corrected.)