Re: Vanguard pink noise

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> 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.
>
> 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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>>> >> >> http://www.vectorlist.org
>>> >> >> ** Please direct other questions, comments, or problems to
>>> >> >> chris@westnet.com
>>> >> >>
>>> >>
>>>

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Received on Thu Sep 23 16:20:33 2010