RE: Asteroids Blues

From: Robert Gonyer <arcade-dawg_at_mchsi.com>
Date: Fri May 25 2007 - 16:01:31 EDT

Sorry, I should have been more specific:

The buzz occurs at all times, about 1 to 2 seconds after power is applied to
the game. All normal sounds can be heard underneath the buzz, but barely.
Turning up the volume turns both the buzz and the sounds up, but the buzz is
always WAY louder than the sounds.

-----Original Message-----
From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Sean McLachlan
Sent: Friday, May 25, 2007 2:50 PM
To: vectorlist@vectorlist.org
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
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Received on Fri May 25 16:01:35 2007

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