SaminVA
Well-known member
Now that my Star Wars board is working it's time to figure out what's wrong with my sound board.
Just to recap, the sound board was completely dead as I tested it in my working game. I replaced the CPU, ROMs, SRAM ,PIA and tested the speech chip in my working sound board so with all these chips tested and replaced I now have music and sound effects but the board still has no speech. Instead of speech you get either nothing, popping or white noise. I made a video which first shows my working sound board in test mode. Then it shows my board with missing speech wile in game play and last wile in test mode. In short all it shows is what sounds should be present in test mode and which are missing on my board. I couldn't find any video of the sound test on the web so I figured it might be of some help if someone is testing their sound board and don't have a working board to compare.
Now for looking for the problem. At first I was thinking their might be a problem with the op amp buffer at 4C LF347 or TL084 because the output of the speech synthesizer pin 8 runs to pin 12 of 4C but testing pin 8 of the speech IC it has the same pops that's coming out the speakers and sense I know the speech IC is good it had to be something inputting to that IC causing the problem. Sense the PIA IC is new and tested good as well as the ROMS and SRAM and CPU and the music and sound effects are working I could rule out that and look for something in the speech section. That left the speech clock which points to 2F CD4069 or 74C04. I tested 2F with my logic probe on both the working board and the bad board and got a very different set of readings .I am putting that info and video together now so I'll post it soon. Maybe someone can tell me if I am on to something or on a wild goose chase.
More on the way
Just to recap, the sound board was completely dead as I tested it in my working game. I replaced the CPU, ROMs, SRAM ,PIA and tested the speech chip in my working sound board so with all these chips tested and replaced I now have music and sound effects but the board still has no speech. Instead of speech you get either nothing, popping or white noise. I made a video which first shows my working sound board in test mode. Then it shows my board with missing speech wile in game play and last wile in test mode. In short all it shows is what sounds should be present in test mode and which are missing on my board. I couldn't find any video of the sound test on the web so I figured it might be of some help if someone is testing their sound board and don't have a working board to compare.
Now for looking for the problem. At first I was thinking their might be a problem with the op amp buffer at 4C LF347 or TL084 because the output of the speech synthesizer pin 8 runs to pin 12 of 4C but testing pin 8 of the speech IC it has the same pops that's coming out the speakers and sense I know the speech IC is good it had to be something inputting to that IC causing the problem. Sense the PIA IC is new and tested good as well as the ROMS and SRAM and CPU and the music and sound effects are working I could rule out that and look for something in the speech section. That left the speech clock which points to 2F CD4069 or 74C04. I tested 2F with my logic probe on both the working board and the bad board and got a very different set of readings .I am putting that info and video together now so I'll post it soon. Maybe someone can tell me if I am on to something or on a wild goose chase.
More on the way