Re: Vanguard pink noise

Kevin Moore wrote:
>
> Dang it I knew you were going to make me work for it.. I'm not 100%
> sure but I think the speaker uses ground for the return. Looks like
> I've got some work to do.
>
> On Sep 23, 2010 3:13 PM, "Rodger Boots" <rlboots2@gmail.com
> <mailto:rlboots2@gmail.com>> wrote:
> > In that case it now gets ugly. Will probably end up being ground noise
> > between amp and speaker (unless speaker doesn't go to ground). If
> speaker
> > connects to ground it has to be the amp ground, no other.
>
As Roger says - make sure the speaker ground is not connected to the
power supply ground directly at the edge connector. It should be on an
isolated pin on the edge connector. The video ground should also not be
connected to the power supply ground. If either share share the 5VDC
ground that could be your noise source - the connection between the pin
and the PCB.

John :-#)#
>
> >
> > On Sep 23, 2010 3:08 PM, "Kevin Moore" <talon.k@gmail.com
> <mailto:talon.k@gmail.com>> wrote:
> >> 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
> <mailto: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
> <mailto: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 <mailto: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
> <mailto: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 <mailto: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 <http://www.flippers.com> "Old pinballers
> never die, they just flip
> >>> >> >> out"
> >>> >> >>
> >>> >> >>
> >>> >>
> >>>
> >
> ---------------------------------------------------------------------------
> >>> >> >> ** Unsubscribe, subscribe, or view the archives at
> >>> >> >> http://www.vectorlist.org
> >>> >> >> ** Please direct other questions, comments, or problems to
> >>> >> >> chris@westnet.com <mailto:chris@westnet.com>
> >>> >> >>
> >>> >>
> >>>
>

-- 
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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