Re: Vanguard pink noise

Well that won't be hard as there are none. The MB3712 is the audio amp, so
all it get's is an input from LM324 to a Volume pot, then that hits the
input of the Amp. Since the pot is removed, I have effectively removed the
input. So the only things connected to the MB3712 are +12v, Gnd, 3 caps, and
a speaker.

Thinking along those lines, I thought the internal resistors of the audio
amp had failed and that was causing my problem. But replacement of a new one
proved other wise.

On Thu, Sep 23, 2010 at 3:02 PM, Rodger Boots <rlboots2@gmail.com> wrote:

> I hate shotgunning, but if the caps have been replaced it's time to go
> after the resistors.
>
> On Sep 23, 2010 2:59 PM, "Kevin Moore" <talon.k@gmail.com> wrote:
> > There wasn't many, but all caps in the sounds circuits have been replace.
> > Tants, Electrolytics ceramics.
> >
> >
> > On Thu, Sep 23, 2010 at 2:56 PM, Rodger Boots <rlboots2@gmail.com>
> wrote:
> >
> >> Replace any small capacitors connected to the chip.
> >>
> >> On Sep 23, 2010 2:53 PM, "Kevin Moore" <talon.k@gmail.com> wrote:
> >> > Well the MB3712 is the last amp in the circuit. I have isolated it,
> and
> >> the
> >> > noise is still present. Grounded the input to the amp, noise also
> still
> >> > present. that is why I thought it was the MB3712.
> >> >
> >> > The only other thing I can think of is that there is noise coming off
> the
> >> > 12v power. But my scope apparently isn't good enough to see it on the
> >> > output.
> >> >
> >> > Kevin
> >> >
> >> >
> >> > On Thu, Sep 23, 2010 at 2:05 PM, John Robertson <pinball@telus.net>
> >> wrote:
> >> >
> >> >> Kevin Moore wrote:
> >> >>
> >> >>> Hello all,
> >> >>> Working on a Vanguard, that has pink noise / static throughout the
> game
> >> >>> play. All sounds, and voice are present, just a constant background
> >> static
> >> >>> noise. At first I thought it was due to a bad MB3712 audio amp, but
> >> >>> replacing it did not help. I've re-capped the power supply, and no
> >> change.
> >> >>> So I'm wondering if anyone has experienced this problem on Centuri /
> >> >>> Vanguard before.
> >> >>> Thanks,
> >> >>> Kevin
> >> >>>
> >> >>> Try removing the volume control - if the noise leaves then something
> >> >> ahead of the volume control is the problem. Then use the schematic to
> >> >> isolate the various sound sources (lift resistors or capacitors that
> >> connect
> >> >> to the input side of the volume control) until you find the guilty
> >> party...
> >> >>
> >> >> John :-#)#
> >> >>
> >> >> --
> >> >> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
> >> >> (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
> >> >> www.flippers.com "Old pinballers never die, they just flip
> >> >> out"
> >> >>
> >> >>
> >>
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> >> >> ** Please direct other questions, comments, or problems to
> >> >> chris@westnet.com
> >> >>
> >>
>

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Received on Thu Sep 23 16:08:15 2010