I found this information on the Vector List. I will be doing more parts replacements.
A post from Bill Boucher:
Re: Armor Attack sounds and rom versions
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From: William Boucher <boucher_at_mnsi.net>
Date: Thu Jun 04 2009 - 17

38 EDT
>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
Thanks Bill