Re: Vanguard pink noise

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.

On Sep 23, 2010 3:08 PM, "Kevin Moore" <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> 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 16:13:29 2010