Re: Armor Attack sounds and rom versions

Thanks for the description..checked everything in that chain and it all seems fine. I'll have to go back on what I said earlier as I played around again with the volume and would say the group 2 is louder than group 1. I changed out both power transistors, all 081's, both 555's, the .33 cap, all logic except the 377, 164, 393's and 06 .. metered all resistors you mentioned below.. is there any pair of opamps responsible for group 2 or do they all have somethng to do with it? See if I can find some of those...

--- On Thu, 6/4/09, William Boucher <boucher@mnsi.net> wrote:

> From: William Boucher <boucher@mnsi.net>
> Subject: Re: VECTOR: Armor Attack sounds and rom versions
> To: vectorlist@vectorlist.org
> Received: Thursday, June 4, 2009, 5:49 PM
> > what do the opamps do? What
> actually amplifies the audio to send to speakers?
>
> The opamps IC19,20,21,22 are voltage-controlled current
> amplifiers (transconductance amps).  They output a
> current signal proportional to the sum of the noise
> generator and the voltage envelope signals that are
> generated by 5 groups of R, C, and Q components.  Each
> of the current signals represents a shaped-noise sound
> effect.  These current signals comprise group one of
> sounds (Tank fire, Lo explosion, chopper, jeep fire, &
> hi explosion).  These current signals then all pass
> through a resistor R90 (100k) where the sum of the currents
> is converted into a voltage signal.
>
> The voltage signal representing the group one sounds then
> goes through opamp IC25 which is nothing but a buffer (unity
> gain amp) and then is coupled by cap C43 into another opamp
> IC26.  The resistors R91 and R92 set the gain of the
> opamp IC26 to about 2.4.
>
> Resistors R7 and R14 bring the Tank engine & squeak
> sounds into IC 26 also. Resistor R7 sets the gain for the
> tank engine to about 0.8.  If the value of R7 is too
> low, the engine sound will be too loud.  R83 brings
> into IC26 the beep signal from the 555 oscillator
> IC23.  The tank engine, squeak, and beep sounds
> comprise group two of the sounds.  IC26 has summed
> together both groups.
>
> The output of opamp IC26 represents the sum of all sounds
> but it is a relatively weak signal.  It goes out
> through the volume pot and returns to the input of opamp
> IC24 (at pin 3).  Resistors R25 and R84 basically set
> the DC gain to about 26.  C39 limits AC gain to reduce
> noise and to keep the amplifier from oscillating.  The
> output of IC24 through R85 and R87 drive the bases of the
> final power amp stage transistors Q12 & Q13 which then
> drive the speaker through R88 & R89.  The two
> diodes D6 & D7 protect the Q12 & Q13 base-emitter
> junctions from damage from reverse-bias voltage that would
> otherwise occur during the half-cycle at which the
> transistor is off.
>
>
> William Boucher
>
>
> ----- Original Message ----- From: "andre" <livnfree_can@yahoo.com>
> To: <vectorlist@vectorlist.org>
> Sent: Thursday, June 04, 2009 10:19 AM
> Subject: Re: VECTOR: Armor Attack sounds and rom versions
>
>
>
>
>
>
> > 28. Since your [engine/squeak/morse] group of sounds
> > are all much louder than the [tank fire, jeep fire,
> hi
> > explosion, lo explosion, and chopper] group, I am
> wondering
>
> I don't think anything is louder really.. i mean the
> chopper and everything is loud as well (proper volume.. not
> cranked up) but the tank engine drowns those noises out. If
> I turn down the volume as you suggested, they all go down at
> those same levels so when it is barely audible, I can still
> hear all sounds but the engine noise overpowers all the
> others. And when the tank speed is at its max, or even close
> to that, it sounds like you have a bad channel on a car
> radio with HUGE engine noise interference comming thru yur
> speakers as well.
>
>
> > if the capacitor C43 (0.33uF) is bad and is not
> passing the
> > output signal from IC25 pin 6 through to R91 (8.2k).
>
> This meters out ok.
>
> > Also, if the value of R91 has gone way up, it would
> reduce
>
> Within range... actually on the down side but in spec.
>
>
> > other group? If that is true, then the problem could
> > be either C43 or R91 or maybe one of the
> transconductance
> > opamps (current amps) at IC19/20/21/22 is leaky and
> pulling
> > all of the sounds from that group down. Anyways, I am
> > getting the impression that there's a gain problem
> between
> > the two groups of sounds. It may also be possible
> that
> > the cap C14 (0.4y uF) is shorted and shoving a big DC
> bias
> > into the TL081 at IC26 pin 2.
>
>
> Replaced that cap and no go.. what do the opamps do? What
> actually amplifies the audio to send to speakers? There
> really isn't too much left on these other than those
> opamps.. even replaced the 555's and a couple more logic..
> think only 2 or 3 chips left outside of the opamps.
>
> >
> > I wish I had your board on my bench for a little
> > while. Why don't you pop it into your transporter and
> > beam it over here?
> >
> I may end up doing that..
>
>
>  
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Received on Fri Jun 5 20:30:07 2009