Quoted from whizz:

What kind of driver board do you have?I had an aftermarket board in mine and the voltages were too high.I had to get my original board rebuilt.That fixed my problem.

Quoted from Quench:

No pop from the speaker on powerup?
When you adjust the volume pots on the sound board, you getting any scratchy noise through the speaker?
With the machine off, measure the resistance between ground and the negative lead of capacitor C8 on the sound board. If you're not reading low ohms then it's a problem with the speakers or connection to them.

Quoted from Quench:

No pop from the speaker on powerup?
When you adjust the volume pots on the sound board, you getting any scratchy noise through the speaker?
With the machine off, measure the resistance between ground and the negative lead of capacitor C8 on the sound board. If you're not reading low ohms then it's a problem with the speakers or connection to them.

Quoted from Quench:

Schematic doesn't show it but if your Xenon has a volume control inside the door, 100 ohms resistance is about the right reading (since it's a 100 ohm volume pot). Have you tried sweeping this coin door volume control full swing to see if you get any sounds/crackling through the speakers?
The game has two 8 ohm speakers and from memory they're wired in parallel, or could it be in series? Can't remember. If they're in parallel you should measure approx 4 ohms across the two speaker wires coming from the harness that connect to the speakers, otherwise if they're wired in series you should measure 16 ohms across those two wires.
One of those two wires connecting to the speakers is ground (with the machine off confirm one of those wires measures zero ohms resistance to ground), the other wire comes from the volume control.

Quoted from Quench:

Can you post a picture of the speaker setup? And clear high res pictures of the sound/vocalizer boards?
Once you're sure the speaker setup is right, carefully check that the TDA2002 amplifier (U9 connected to the heatsink) on the sound board has 12V power at pin 5.
Also grab a screw driver and touch the + leg of capacitor C5 (which goes to the input of the amplifier) with the screw driver tip while holding the metal part of the screw driver. Do you get any speaker hum?

Quoted from Quench:

Can you post a picture of the speaker setup? And clear high res pictures of the sound/vocalizer boards?
Once you're sure the speaker setup is right, carefully check that the TDA2002 amplifier (U9 connected to the heatsink) on the sound board has 12V power at pin 5.
Also grab a screw driver and touch the + leg of capacitor C5 (which goes to the input of the amplifier) with the screw driver tip while holding the metal part of the screw driver. Do you get any speaker hum?

Quoted from Quench:

Those door volume pots often go flakey.
So it looks like the orange wire to the speaker is ground.
The white wire to the speaker comes from the coin door volume pot.
Measure the resistance from the white wire back to the negative lead of capacitor C8 on the sound board. As you adjust the volume control on the door the resistance reading should change from zero ohms when set to max volume to 100 ohms when set to minimum volume. If you're getting readings way beyond 100 ohms, it's likely the swiper arms inside the volume pot is going open circuit.
You can buy a replacement volume pot from Jameco:
https://pinside.com/pinball/forum/topic/new-6-inch-speakers-found#post-4488849
Or you can fix yours. It's held together by 4 tabs. Bend the tabs up so the volume pot assembly comes apart. Bend the four internal swiping arms out a little so they make better contact. Clean the centre ring that the inner swiping arms touch. Then put it all back together.

Quoted from Quench:

Those door volume pots often go flakey.
So it looks like the orange wire to the speaker is ground.
The white wire to the speaker comes from the coin door volume pot.
Measure the resistance from the white wire back to the negative lead of capacitor C8 on the sound board. As you adjust the volume control on the door the resistance reading should change from zero ohms when set to max volume to 100 ohms when set to minimum volume. If you're getting readings way beyond 100 ohms, it's likely the swiper arms inside the volume pot is going open circuit.
You can buy a replacement volume pot from Jameco:
https://pinside.com/pinball/forum/topic/new-6-inch-speakers-found#post-4488849
Or you can fix yours. It's held together by 4 tabs. Bend the tabs up so the volume pot assembly comes apart. Bend the four internal swiping arms out a little so they make better contact. Clean the centre ring that the inner swiping arms touch. Then put it all back together.

Quoted from jj44114:

Test the total ohms at the connector that plugs into the sound board

Quoted from Quench:

The parallel wiring in that picture on those speakers looks factory. The TDA2002 amp is designed to drive loads down to 1.6 ohms, so a 4 ohms load isn't going to blow it. Remember the speaker load is hanging off the 100 ohm wirewound volume pot anyway so under normal circumstances the amp won't see a load that low.
OP, are you reading 100 ohms at the output of the sound board no matter where you have the coin door volume set?
When the coin door volume is at max volume position you should read 4 ohms. When the pot is at minimum volume you should read 100 ohms. The resistance reading should change as you adjust the volume.
If you always read 100 ohms no matter where the volume pot is positioned, it says you've got an open circuit between the volume pot and the speakers, or both speakers are open circuited (unlikely for two of them to go but still possible).

Quoted from Quench:

Cool, ok the speakers are out of the way now.
What voltage do you measure on the "+" leg of capacitor C8 on the sound board? That's essentially output of the TDA2002 amplifier and it should be about half the voltage you measured at the power pin (pin 5) of the amplifier. Pin 5 was previously measured at 15 volts, so the + leg of C8 should be around 7.5 volts.

Quoted from Quench:

Pretty likely.
Check the input signal voltages to the amp. Pins 1 and 2 should also be about half the amps power supply voltage.
For easier access, the "+" leg of capacitor C5 goes to pin 1 of the amp, and the "+" leg of capacitor C7 goes to pin 2 of the amp.
BTW, you should also check if any of C5, C7, C8 or C25 are shorted.

Quoted from Quench:

The input and output voltages at the amp should be centre biased (half the power voltage). You're getting zero volts on each. It's time to replace that TDA2002 amplifier chip at U9 on the Sound Plus board. BTW does the heatsink it's attached to get warm after a few minutes of being on?
Inspect the back of the board when you pull it out around the amplifier for anything that looks obviously wrong (damaged).

Quoted from Quench:

Good luck, let us know how it goes.

Quoted from Quench:

Good luck, let us know how it goes.

Quoted from barakandl:

TDA2002 is obsolete. You will have better luck looking for TDA2003 which is a replacement but still obsolete from STM. A lot of the STM parts you see on eBay are counterfeit but still work. I have read people say the counterfeit TDA2003 lack short circuit protection like the real ones do but otherwise ok. Not sure what to expect from TDA2002 marked stuff from eBay tho.
There is still a company in Taiwan that make legit good TDA2003 which is a drop in replacement. I have used plenty of them.
http://www.unisonic.com.tw/datasheet/TDA2003.pdf
Have you checked TP4? When sound is triggered and should be playing noise TP4 should start to pulse and be flat 0v when no sound. If you get action on TP4 the CPU is probably running OK.
Then check TP6. When sound is playing you should see ~1 VAC there when sound in progress. If nothing there but you get action at TP4 replace the sound chip.

Quoted from barakandl:

It is normal to get some display noise to come out the speaker when volume is adjusted high. That means the amplifier and volume control is probably working fine.
TP4 is the VMA. It should be flat 0v when no sound, that is normal. If you get pulsing there when sound would be playing the sound board CPU is running. I don't think it should ever be solid high / 5v.
For TP6 set DMM for lowest range AC volts. Repair book says it should be 0.35vac +/- 1vac when sound is playing and 0vac when no sound. If it never changes from 0v then the sound chip is never making sound. Since the VMA is active when sound should be playing I'd suspect the sound chip or maybe the PIA. With a logic probe you can watch the PIA ports connected to the sound chip (labeled DA0). They should go active when sound should be playing.
The speech board complicates things. An issue on the speech card could mess up the sound board. I don't know what to expect from the software if the speech board is not connected, but I'd assume it would work, so maybe try with the speech card ribbon cable off.
The bally repair book is pretty good for this board. It doesn't talk about the speech board tho. Around page 75.
http://arcarc.xmission.com/Pinball/PDF%20Pinball%20Misc/Pin%20Repair.pdf

Quoted from EdHess:

This is totally not true! I bought one from Marco 2 weeks ago. In fact somebody goofed in shipping. When it arrived there was a 2nd one on top of the first. Not realizing but wondering why it was so thick, I pushed it into the socket. Then I realized the legs on the 2nd where pinching it to the first. Pryed it off. So I have a spare. If you want it or Marco doesn’t have anymore let me know. But they are still available and not obsolete unless i just got lucky. But still showing in stock
https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=Ay3-8910