Williams Defender no sound repair log

pinballDan

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Just got done with a Defender and thought I would share what I found wrong with it.

The Game would boot up just fine, but did not make the start up sounds, you could coin it and it would add credits, you could start a game, but none of the controls would work, so it would not play.

Game had no sound at all, checking all the voltages were good, pulled the 6808 IC9 CPU chip on the sound board and put in a new one and then had all my sounds.

Went to check why the buttons were not working and now they are. Put the bad CPU chip back in and they quit again.

So a bad CPU chip on a sound board was stopping the controls (and sound) from working.

Got to love them old Williams Videos

Now to fix the Joust.....
 
Went to check why the buttons were not working and now they are. Put the bad CPU chip back in and they quit again.

So a bad CPU chip on a sound board was stopping the controls (and sound) from working.
Any theories as to how the sound CPU was keeping the controls from working? I can't think of an obvious connection between the two, since the data paths and bus/control interfaces are isolated. The player start button atleast worked though right (since you were able to start a game)? Baffling ..

LeChuck
 
Any theories as to how the sound CPU was keeping the controls from working? I can't think of an obvious connection between the two, since the data paths and bus/control interfaces are isolated. The player start button atleast worked though right (since you were able to start a game)? Baffling ..

LeChuck

Red Herring. While playing with the sound card it is likely that he bumped something which reconnected the ground wire to the controls.

The sound card is isolated from the data bus on the MPU board and the I/O card by the PIAs on the ROM card and the sound card. The PIA on the ROM card is the active side and the PIA on the sound card is the passive side. Even if the PIA on the sound card decided to send, the ROM PIA is not receiving. The worst that would happen is that it would become confused and ignore the coin door switches and the coin door buttons.

ken
 
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