Re[2]: Asteroids Blues

-----Original Message-----
From: Sean McLachlan <sean@lithoflexo.com>
To: vectorlist@vectorlist.org
Date: Fri, 25 May 2007 13:50:29 -0600
Subject: Re: VECTOR: Asteroids Blues

>
> Robert Gonyer wrote:
> >
> > Good thing it s a long weekend so I can forget about my troubles, lol.
> >
> > Board #1 is the one that was buzzing really loudly. I am 100% sure
> > it s the board, because another board (that used to work 99%) didn t
> > buzz at all in this cabinet. I replaced all the caps on the board,
> > plugged her in in anticipation that I was gonna get a game in . and
> > BUZZZZZZZZZ . I couldn t believe it. Any other ideas?
> >
> > Board #2 is the one that you all helped me find a bad chip using
> > freeze spray. It turned out to be the one directly above the CPU.
> > (74LS245N) Sound like the right part? I know it didn t match the # s
> > on the original, but I figured Bob knew what he was sending me, and it
> > was the right pinout. Symptoms before was that the game would play
> > fine for a couple hours, then it was start flaking out as it got warm.
> > Freeze spray to this chip brought it back to life. I replaced this
> > chip, now it flakes out constantly, won t even come up. Clicking from
> > the coin door, random noises, etc. I have replaced lots of chips
> > before, so I don t THINK I did it wrong, but it is certainly possible.
> > Any other ideas?
> >
> > Maybe I just need to send them both in and have them gone over .. This
> > is too frustrating for me!
> >
> Robert,
>
> In re reading your original post, you said that the buzz occurs during
> play. Is that the ONLY time it happens? No buzz during attract mode? And
> you also said you can hear the game sounds, but can you hear all of
> them? What I getting at is, from the schems, each sounds has a distinct
> circuit. If one sound is missing, that may tip you off as to which
> circuit has failed and is blasting noise into the audio.
> Trying to think about this logically, if any of the individual sound
> circuits had failed, wouldn't that only screw up the sound when that
> sound circuit was triggered?
> The heartbeat/thump sound is always playing, and if the 555 timer was
> bad, that could give a constant noise. The heartbeat would be missing in
> that case.
> If all the sounds are present, and the buzz is constant, and there is no
> buzz with another board, then I'd look in the Audio Output section of
> the schems. There is an LM324 chip, P11, that mixes, splits and then
> inverts the sounds to get the 2 audio outputs. If you have already
> changed out the caps in the audio section, that chip is where I'd look
> next. I don't know how to test it though. Anyone else know? Oscope?
>
> --
> Sean McLachlan

the only way i can think of is to try to trigger each sound with a logic-pulser or a jump-wire to ground and then compare what you hear with a good board.

i hate these types of problems, it reminds me of space-invaders repairs!

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Received on Fri May 25 15:55:54 2007