Terminator 2: Judgment Day
Williams, 1991Is it normal for WPC A-12738 audio boards to get louder as the game warms up? I have the volume set at 7 which initially seems very quiet, sfx are faint, and barely any noticeable bass. After about 30-45 min of game play it gets louder and sounds great! For the heck of it I pulled the board and reflowed all connectors, reseated ROMs… no difference. Thoughts? Thx!
i am not that familiar with this board, but sounds like failing electrolytic capacitor.
To start i would check the +12 and -12v cold(assuming it uses those voltages) and then check again once warm.
Ok... I'm getting -12.1 and +11.9 at U3 and U4. Seems voltage checks out fine? From a lot of what I've been reading this in fact may be a capacitor on it's way out but I'm not sure which exact one to start at. 
I'm considering just replacing all the caps at this point. Soldering is fun. 
Getting closer figuring this out I think. Here's what I did just in case anyone has a similar problem down the road.
I replaced the 47uf caps at C15, C18, C34, C36, C38, and replaced the 1uf tantalum caps at C46 and C47. While I was at it, I also corrected R23 and R24 to 150k ohm from the 56k ohm that were originally in place. Finally, I read about adding a 4.7 ohm / 2 watt resistor to the backbox speakers to bring the mids and highs down a bit allowing more bass to the foreground... holy crap what a HUGE difference!!! I can hear Arnold much better, I'm hearing sounds in the game I didn't before, very solid (not cabinet shaking) bass, and I can keep the volume up around 9-10. Sounds are clear even at higher volumes. Before I'd have it at 7 and it was just noise.
It still gets a tad louder after warming up but not a dramatic difference as before and the sound isn't all high end nails on a chalkboard. I still have some poking around to do...
Quoted from scupbucket:Getting closer figuring this out I think. Here's what I did just in case anyone has a similar problem down the road.
I replaced the 47uf caps at C15, C18, C34, C36, C38, and replaced the 1uf tantalum caps at C46 and C47. While I was at it, I also corrected R23 and R24 to 150k ohm from the 56k ohm that were originally in place. Finally, I read about adding a 4.7 ohm / 2 watt resistor to the backbox speakers to bring the mids and highs down a bit allowing more bass to the foreground... holy crap what a HUGE difference!!! I can hear Arnold much better, I'm hearing sounds in the game I didn't before, very solid (not cabinet shaking) bass, and I can keep the volume up around 9-10. Sounds are clear even at higher volumes. Before I'd have it at 7 and it was just noise.
It still gets a tad louder after warming up but not a dramatic difference as before and the sound isn't all high end nails on a chalkboard. I still have some poking around to do...
Nice. Sounds like you got it covered. I wouldnt worry about it to much. Heat can change resistance of components. I know in my car if i crank up the volume i notice it quiets down after a few minute.... probably because the amps are heating up.
I will have to look into adding the resistors to the speakers. My Getaway probably uses the same setup.
Andrew
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Buffalo, NY
Ightham