2804 EEPROM / Atari System 1 Question

FlashShift

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There's a 2804 used for NVRAM on my Sys 1 board. While trying to debug a hum through the audio and the music being much softer than the other sounds, I pulled it just because I could... both the music and the hum cut out, but the sound effects and speech still play. Checking the schematic, there doesn't appear to be anything sound related going through this line. Why would pulling the chip have this effect?
 
I think what is happening is the 2804 is bad, and so is not responding, and so is getting held high for a response. The I/O coming across pin 9 is causing noise on the line and dragging down the level of the music data traveling over the same bus. At least that's my hypothesis. I have a 2804 on order, we'll see how it pans out.
 
Answer: it has absolutely nothing to do with sound. But pulling it out, loosened the smaller of the two Yamaha chips in its socket and it stopped making contact. Resoldered a better socket and sound is back. Now I just need to replace both yammies and hopefully the sound will be better. It's coming out staticky straight from the FM chip.
 
FWIW replacing both Yammies fixed the sound. The buzz was coming straight from the 2151 synth chip and it was super quiet because of the DAC (YM3012)
 
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