I have a Gottlieb Volcano (system 80). EDIT: The Sound & Speech board was replaced sometime in the past with a B-20887-3 from a system 80A model PV810 (Caveman)

Ground modifications done. New electrolytic caps on most of the boards including the sound board. The big orange capacitor was replaced in the past.

95% of the time the game boots fine. For the other 5%, there are booting issues and the consensus seems to be that I need to do the CPU reset circuit modification. Parts on the way. EDIT: Reset modification successful and MPU booting issues resolved. This sound issue remains.

Meanwhile, sometimes I get a random sound from the sound board on the switch click for power up (and power down). Sometimes it's a groaning sound as you can hear for yourself in the YouTube video. Other times, it's just a hiss barely audible to louder. Whatever it is, it's never louder than the master volume setting.

When I add credits, start a game, or attract mode kicks in, the groaning or hiss immediately stops and I get the normal game sounds. The problem never occurs after the initial power-up.

The sound & speech board passes all the self-tests.

Could this be something flaking out on the driver board? Like Z3 or Z13? EDIT: Problem still occurs with driver board unplugged, effectively eliminating the MPU and Driver as the cause.

The power supply for this game's sound board is down in the main cabinet under the playfield. I have not seen anything about mandatory fixes, updates, etc. in Pinwiki or Clay's guides for this other sound board power supply.

I am open to any suggestions about how to fix this.

Thank you!

EDIT: This particular post seems to be a red herring. Problem occurs with Driver board unplugged.

I checked all sound outputs with logic probe on Z13, both after booting normally and during the buzzing. All outputs are the same under both conditions.

After checking further, problem somehow seems to be related to "Sound 16" output which goes through an extra connector.

Following the Volcano schematics for "Sound 16":

Z3 pin 7 output on Driver board
-> A3-J2 pin 9 leaving Driver board
-> A7-J3/P3 pin 6 Molex connector with 0.093" pins in head
-> A6-J1 pin 2 input on Sound card

After unplugging and plugging in the A7-J3/P3 Molex connector, the problem became less frequent. EDIT: Problem still occurs without driver board connected, which means A7-J3/P3 is not even in the circuit during this case.

What is "Sound 16" and why is it routed differently through the A7 connector when it simply ends up at the Sound board like the other 4 sound triggers? Can anyone explain this?

Thank you for the explanation.

The ground mod is correct and ground is solid, but I still had my doubts about all the connections and connectors for the signal wires. So I bypassed around each of them with jumpers. No improvement.

Then I looked down inside the cabinet. The power supply for the sound board has another Molex connector so I jumped the grounds off the sound board power supply over to the ground bus. Again, no improvement.

Finally, I noticed how the 110 VAC cord was routed...

110 VAC routed with DC signals

It's tied tightly to a bundle of low voltage signal wires that go up to the head! You should never route the AC supply voltage in close proximity and parallel with low voltage DC signal wires. It was obvious that when somebody replaced the original cord, they tied it off here with orange zip ties. If I'm wrong and all the Gottlieb system 80 games routed the 110 VAC bundled with the signal wires, please let me know... and then maybe add this to the list of modifications.

Fixing it as such...

110 VAC re-routed

Where it's unavoidable and the 110 VAC needs to be near the DC signals, it's ok to cross them over each other perpendicularly.

Since the cord was routed so poorly, I decided to check the hot and neutral wiring... again wrong. In the US, in a 110 VAC plug/outlet, the neutral side is the wide blade and the hot side is the narrow blade. If the wires are color coded, neutral is white, hot may be black or red, and ground is green. This cord is not color coded and the person who replaced it had swapped the hot & neutral. Thankfully, this machine does not bond the neutral to ground.

Swapping hot & neutral can be a huge issue in many circumstance. In this machine, this mistake means:

• the main fuse was on the neutral side so if the 110 VAC was accidentally shorted out, the fuse might never blow depending on return path
• plugging a tool with a metal case into the service outlet might give you a surprise
• the power switch was only disconnecting the neutral side so...
• the main transformers would ALWAYS have 110 VAC on one primary leg even when machine is off
• numerous random hazards, etc.

Anyway, I re-routed the 110 VAC and wired the hot & neutral correctly. The sound issue has improved tremendously. I think it may have happened one time before I found the hot/neutral issue, but time will tell if it's fixed for good. I may look at replacing the AC filter or installing some kind of internal surge protection as it's obvious now this sound issue is being triggered by AC noise on power up. I also plan on looking closer at the capacitors on the sound & speech power supply.

Problem still randomly happening.

On the Sound & Speech Power Supply, the 3 diodes, 2 resistors, and 2 capacitors checked out good.

I remounted the transistor and voltage regulator with fresh heat sink compound.

Sound and Speech Power Supply

I think the power supply is fine and all the voltages are within spec...

+24 VDC
-12 VDC
+12 VDC
+30 VDC

I also verified these same voltages at the Sound & Speech card to make sure the connections are good.

I'm going to get a new line filter just to eliminate any additional interference on power up. Does anyone have the Gottlieb part number for this? It's the very first device the 110 VAC power cord is connected to.

Line Filter

I don't even know how that's possible. As stated, the problem still occurs even when all connectors are bypassed and additional grounds in place.

When I have the driver board removed from the machine, the noise is still randomly happening on boot and only on boot. Grounds are jumpered and the only connectors in play are at the sound card and power supply for voltages and speakers.

With no driver connected, there cannot be any MPU triggered sounds. This problem only randomly occurs on boot and NEVER happens during play. IMO, bad connections are always bad connections and should also manifest at other times besides boot. It’s like something is only spiking on power up. For only $10 I’ll try a new line filter while I continue to troubleshoot.

Meanwhile whatever the issue, I can reproduce while the sound & speech board is completely isolated to nothing but the sound & speech power supply and speakers. To me it sounds like one of the speech patterns gets triggered and stuck at the moment power (spike?) is switched on. Is there any other clever way to troubleshoot or isolate?

I installed a new line filter from PBR today. I don't regret as the 40-yr-old filter was probably not doing anything.

Although it's happening more infrequently, this did not eliminate the issue.

So now what to look for? Again, it also happens while the driver board is unplugged, so that eliminates the MPU logic and triggers.

The four voltages from the sound & speech power supply are correct. Maybe the DC isn't smooth enough and I need new capacitors on the S & S power supply? However, the big cap on the S & S power supply looks the same vintage as the main cap on the machine, which is not the original. I just don't have enough experience with this, but it seems like a power issue since the problem only ever happens when clicking on the main power switch and it's immediate.

It's almost like the sound board needs its own anti-thunk reset modification to keep it from activating until after the power settles down.

Finally got around to re-pinning the connector on the sound & speech board. This seems to have cleared it up for good. Since problem was happening with driver unplugged, ruling out the sound triggers, it had to be a loose power connection causing an intermittent spike on power up. I powered it up about 20 or 30 times in a row without one single sound being triggered.

Spoke too soon! This issue came back today.

• Fixed 110 VAC hot & neutral swapped
• New line filter
• All new Molex edge connector pins on A6-J1
• Solid ground verified
• Tested components on Sound & Speech power supply in lower cabinet
• Tested all voltages on Sound & Speech power supply at A6-J1 connector
• Replaced all electrolytic caps on Sound & Speech board

Still happens with Driver board unplugged (rules out Driver and MPU). Sound & Speech board passes the test routines without issue.

This issue only ever happens on power up. Never happens while machine in attract mode or during a game.

Anyone with any more ideas, things to double-check, anything?

Please anyone?

Board was re-capped just prior to posting this thread - maybe 3 or 4 weeks ago tops. I purchased these (Changxin) from Marco Pinball. Just to note, it's the same issue both before and after changing these caps.

Changxin cap from Marco

I also replaced the C33 capacitor that was only rated for 25 volts, in the 30 volt part of the circuit, with a 50 volt version.

Oh boy... so the capacitors I recently got on Amazon were factory-reject Chinese junk... sent back. I figured I could trust Marco. The caps I got from Big Daddy are JNC brand, which are also Chinese. The fuses I got from PBR looked like they were previously used in a machine (PBR blamed Chinese manufacturing). Does anyone manufacture caps outside of China these days? EDIT: Rubycon from Japan

Capacitor brand aside, any clue how I can narrow the troubleshooting down? I assume there's something on the board that is being extra sensitive to a spike on power-up. Or the sound & speech power supply itself is due for new caps?

Yes, thank you. I realized this after my last post.

Any idea how I can troubleshoot this further rather than just throwing more capacitors at it?

If original I would replace without hesitation, but as mentioned previously, they're not. They were replaced when big orange main cap was done. So it would just be another part$ guess. I’m looking for some analytical troubleshooting help. Even if I borrow a scope, I’d need data to compare. Thank you!!

With all the system 80 games out there, and all their old caps, isn’t it odd that nobody else has been here on Pinside reporting a similar problem? Especially since rebuilding this particular S&S power supply is not covered in the PinWiki, this should be a very common issue if caused by aging caps. Just thinking out loud. Appreciate the help.

I did a little more troubleshooting...

I confirmed the noise being generated is from the "speech" section of the board. The two trimmers on the board control the volumes separately...

•  R15 is the "sounds" volume
•  R16 is the "speech" volume

While the problem is happening, the volume of the tone can only be changed by R16. The sound from the YouTube video as well as the quieter hissing... both controllable only by speech volume.

So I overlooked C36... going to change it right now. Not sure how I missed it... a big electrolytic... 470 µF, 35 volts. I don't think it will solve this issue because it's on the output side of the amplifier, while this sound problem is coming from somewhere in the speech circuit.

I also toggled all of the S&S DIP switches several times to clean as suggested in Clay's guide. Not sure if this did any good yet.

It seems that both PinWiki and the other guide focus on problems such as missing sounds, missing speech, no amp, triggers from the MPU/driver, or no sound at all. There's really no information in there about troubleshooting spontaneous speech sounds and false triggers when the driver is unplugged.

As predicted, changing the C36 capacitor made no difference, nor did "cleaning" the DIP switches. Nor did tinning the bare copper on the edge connector.

Really hoping there's somebody who has seen this problem before and can shed some light on this.

Thinking it's a spike or noise on power up, I methodically jumped a 4700 µF cap to each voltage on the sound & speech power supply... one side to ground and the other to power... and this made no difference. Same sound.

Then I visually inspected the big caps in the cabinet. Besides the "big orange" on the 38 VDC (which is not orange - had already been replaced at one point), there is another called C1 on the 12 VDC rectifier. This one has definitely been replaced at some point, but it looks pretty old. It was too big for the original mounting clip so you know it's probably something even older that somebody pulled off a shelf or recycled it from who knows where. This is the 12 VDC that goes into the main PS in the lightbox... the same 12 VDC that is used to generate 5 VDC for logic and processors including the sound & speech board circuits. EDIT: As per PinWiki, the 12 VDC capacitor is a.k.a. "big orange". I was confused because my C1 is not in same position on the board as the PinWiki photo.

As a test, I jumped in a cap from 5 VDC to ground and I still have the issue, but now it's changed into a completely different sound. Remove the cap and the next time it happens, it's back to the original problem sound.

I think I'm finally on the right track and here's my latest working theory:

I already know the sound is being generated from the speech circuit. The 12 VDC that powers the SC01 voice chip is coming from the sound & speech power supply - ruled that out. The 5 VDC, however is coming from the main PS, which is generating it from the 12 VDC that is being conditioned by questionable C1 in the lower cabinet. This is the same 5 VDC that is used to generate the various spoken words. I don't think it can be coming in through the U13 logic chip since the processor hasn't fully booted, this spike must be coming straight through the RP1 DIP resistor package and the SC01 voice chip is converting it straight into speech - which actually sounds like a long deep groan. Ironic. LOL.

Again, once powered up, sound & speech operates perfectly fine, so another reason to rule out any of the logic chips.

speech circuit

For sure I am going to replace C1 in the cabinet and probably the other two or three caps just to be sure.

Like I said before, what I don't understand is why this wouldn't be a more common issue with all of the sound & speech machines before these capacitors are replaced.

EDIT: As per Clay's Guide:

This is where the designer of this board was seriously off his face. It’s really quite clever but unnecessarily complex compared to what modern machines use.

This circuit all revolves around the now defunct SC01A chip (U14). This chip produces phonemes (I had to look this word up)- basic units of speech. Vary the clock frequency to it (Pins 15 & 16) and it speaks- Wow! It can also produce sound effects the same way.

See the diagram where I’ve outlined the sections of the board and look at the speech output section. Basically two latches (7475 – U11 and U18- controlled by U10) receive data from the MPU , pass it through a DAC (U19) which converts the signal into a proportional current. This then passes through a frequency adjust LM741 (U21), a couple of transistors (Q1 and Q2) then into the speech chip (U14) at pins 15,16. This is the variable clock signal for the speech chip. The pot R16 controls the speech volume. The R6 is a "frequency adjust" pot, and R13 is an "amplitude adjust" pot.

Data is also sent to the speech chip from MPU to the Level Shift 74LS05 (U13), pulled up by a Dip resistor (RP1) and into pins 9 to 14 of the speech chip.

Voice and effects pitch is varied from the MPU by making Pin 13 of Latch 7475 (U9) high then transferring the data to U12 then onto Pins 2 & 3 of the speech chip(U14).

Yes, yes. As soon as anything triggers a sound the groaning noise stops.

• Adding a credit
• Starting a game
• Attract mode

Then it’s perfectly fine, no matter how long left on, until some random future power-up of the machine. (You can sometimes hear the same sound for a split second on power-down as well.)

It’s simultaneous with the mechanical action of the switch. I’ve also made it happen by plugging in 110 VAC power with switch left on. Definitely seems like a power spike.

EDIT: I have all five of the cabinet capacitors on order from Mouser... C1 through C5... that's C1, C4, and C5 on the main cabinet board and C2 and C3 on the sound & speech power supply. I've owned the game since 2012 and the person before me had it for more than a decade. I believe these caps were changed sometime before the previous owner got it... probably when it was pulled from the arcade... so maybe 20-25-30 years ago? As far as hours of time on the caps, that's impossible to know because I didn't use it at all 2013 through 2020. It's a worthy investment but just FYI on electrolytic caps... yes, they have a rated number of hours that seems low, however that lifespan rating is based on their max temp rating... 85°C (185°F) or 105°C (221°F)... there is NO WAY the cabinet air temp or the caps in this cabinet are ever going to see 185° let alone 221° F. And for every 10° C below the max temp rating that it runs, the rated number of hours doubles. Pulling out crappy caps from machines that spent years in arcades decades ago makes tons of sense.... pulling them out of a machine that already had all caps replaced after it came out of the arcade and then sat in a residence getting played occasionally... I'm not so sure. In my case, C1 looks really really old even though it's not original... and while I'm ordering one, might as well get all five for a few more bucks. They're all reputable brands that meet or exceed the specified voltage rating, have a case diameter that fits the existing metal clip, and have the same kind of electrical connection. Plus as per PinWiki, I upgraded C1 from a 6,800 µF to a 12,000 µF so it should be extra smooth and creamy.

I changed C1 today. That's the capacitor formerly known as "big orange". I upgraded to a 12,000 µF from Mouser. Not only selected for capacitance, voltage, and brand, I carefully selected one that also had the physical diameter to properly fit into the original holder clamp.

After testing C1, I went ahead and changed C2 through C5 as well... so that's all caps in main cabinet including the sound & speech power supply.

Seems to be working great, and so far, issue is gone. Time will tell.

Again, quite perplexed about why not more people with sound & speech are reporting this issue if caused by the famous orange capacitor.

Yes, that is a given. Or in my case, the cap was actually changed once before, so I blindly assumed it was fine... *shrug*

Thank you guys... I feel a lot better about it now.

Makes sense. DIP switch #5 is the toggle for background sound and #6 is the toggle for speech.

Which revision of the sound & speech board does yours have? Somehow mine ended up with the latest, B-20887-3 (revision 3). Does not match the Volcano manual... had to track down the correct A6 schematic from the "Gottlieb Star Series System 80 Service Manual"

Or another theory... because it wasn't the C1 capacitor causing the issue, or any capacitor apparently, since now I've changed all of the electrolytics, plus a few other kinds.

Unfortunately, the problem came back today! I don't know whether to laugh or cry, and I hate blindly throwing parts at a problem.

Or it's still the C1 capacitor because a 12,000 µF Nichicon just isn't good enough?... no idea. Maybe it's time to borrow a scope?

At some point in this game's life, somebody replaced the original sound & speech board with the latest revision: B-20887-3

This is revision 3 and it does not contain any components soldered to the back like the previous revisions.

Unfortunately, my Volcano manual only contains the revision 1 layout and schematic that came with the game. I obtained the B-20887-3 layout & schematic from the "Gottlieb Star Series 80 Service Manual".

Since this is the 3rd revision, some components have been moved around, added, or designed out such as C35. It's still shown in the bill of materials, but C35 is not in the schematic, and the holes are filled with factory solder. Also, RP1 DIP resistor bank is listed as a 222 (2,200 ohm) ... however, the actual component on the board is a 102 (1,000 ohm). So now I know not to completely trust the bill of materials or schematics.

When troubleshooting the original issue further, I noticed that the space on the board for capacitor C22 is empty, the holes are not filled with solder, but yet it's showing on the rev 3 layout and schematic. It's listed as a 300 pF "CMD" (ceramic metal disc, I presume).

It's part of the clock circuit for the speech chip. I don't know if this missing capacitor is the root of my issue, but if it's supposed to be on my board, I'd like to install one there and rule it out.

Since I don't completely trust the schematic, can somebody with the same revision sound & speech board (B-20887-3) please confirm whether or not C22 exists on your board and if it's a 300 pF ceramic disc. Thank you!

C22 on sound and speech B-20887-3

clock circuit for speech chip

I would agree. Just trying to confirm the value listed in the documentation is correct.

The main problem with the PinWiki photo is the same as the schematics I obtained... both show part number the same version 3 board. However, the DIP resistors, RP1 on the PinWiki board is 2.2 kΩ, and the RP1 on mine is 1 kΩ ("102" = 1, 0, plus 2 more zeros)

RP1 = 2,200 Ω

RP1 = 1,000 Ω

I know... everything in documentation says 2.2 kΩ. Both RP1 and RP2 on mine are same chip... 1 kΩ

It sure looks original (see closeup photo of my RP1 and examine solder job). My sound board is really clean and looks the newest and cleanest out of all the boards in the machine. Until I changed the caps, all the solder looked original and untouched.

Notice the Bourns logo and part number on my chip: 16-2-102. This matches the Bourns numbering scheme as per their datasheet. The Gottlieb bill of materials also uses a Bourns style part number (4116R-002-222), but the PinWiki photo shows a DIP that is a different brand and numbering scheme. My guess is there's yet another version of the revision 3 board, and there may be even newer schematics out there in a specific game manual. How many Gottlieb games used these B-20887-3 sound & speech boards and what/when was the last one?

According to PinWiki "PV810" is Caveman... my board came from Caveman... since Caveman is system 80A, maybe that explains the discrepancy in certain parts?

serial number on A6

Issues now:

• How to verify C22 (I'll probably just try a 300 pF)?
• How to get proper schematics to match this version of board? Anyone have a Caveman manual?
• Does C22 have anything to do with this issue (try it and see)?

It's crazy. These resistor DIPs are a real mystery. Since my previous theory was a spike coming into the phoneme triggers from 5 VDC through these DIP resistors, maybe this is an important issue after all?

Regardless, I think getting C22 back onto the board would be a good idea. Maybe once I get my hands on the A6 schematic from Caveman, I need to carefully trace out my board and compare component by component.

I presume that's the issue. When I clip a capacitor onto the 5 volts, the groaning was still randomly triggered but it changed to a different phoneme.

I put the reset generator modification on the MPU and the Driver. This groaning issue was happening before. It also happens with the Driver board unplugged so that completely rules out any sound triggers from the MPU through the Driver. I also looked at the voltages coming from the sound & speech power supply and they are all testing good. Capacitors added to these voltages for filtering had no effect on the problem.

Yes, all pins measure 1,000 Ω

I will definitely have to investigate this idea... unfortunately, I cannot find the scope I knew I used to have.

The clock frequency adjust pot controls the pitch of the speech. When the speech started sounding like chipmunks, I touched this pot and got it slowed down a touch and it started sounding normal again. So not entirely sure that changing this frequency would let transient noise through. No idea though.

Maybe C22 is critical for this? I have to see if I have any 300 pF caps handy.

Thank you!

After reviewing the Caveman schematics, the RP1/2 mystery remains. The layout and schematics from the Caveman manual appear to be identical to those from the Star Series 80 service manual. Same value for C22 and also shows a 2.2 kΩ value on RP1/RP2.

C22 is listed as a ceramic metal disc, CMD, valued at 300 pF without giving a voltage rating. I dug through my stash... the closest I found were a 100 pF and a 220 pF. Wired in parallel, those would be equivalent to 320 pF. Less than 7% over 300, close enough I think, especially since there's zero farads there now. Lol.

I won't have a chance to get to this today. Then it's going to take a day or two to see if C22 had any effect.

No, RP1 and RP2 are original to this board and both testing fine.

Exactly my thought. It’s behaving perfectly normal after first speech sound happens.

The issue seems to have been improved both when I re-pinned the connector and changed the C1 capacitor. But it’s still there. Happened about 25% of the time yesterday and today not at all. I’ll get something put in for C22 and give it more time to see if it’s going to come back.

As far as the circuit, I was reading a lot on pinwiki. Apparently pins 15 & 16 on speech chip are like a toggle. The phoneme inputs are there but supposed to be ignored until these pins come on. So maybe a 5 V spike is coming through the clock and activating the chip, where C22 is not there to clamp it. Just my latest working theory.

UPDATE:

I flipped the A6 board over for another closer inspection. All solder appears factory except for my new electrolytics, DIP switch bank, and U16 (74LS04).

I installed my 320 pF equivalent (220 + 100 pF in parallel) ceramic capacitor in C22. What a weird turn of events. It made a strange oscillating or pulsating sound, very quietly, on power up. When adding a credit and starting a game, the game sound was barely audible and it was not even close to normal. Hard to describe, but the sound was way more screwy than simply pitch and volume.

Removing the C22 put the sound back to normal. Now we know why C22 was originally removed... but obviously, this was/is not the correct "fix".

I'm hesitant to mess with these. It did not simply sound like the frequency was low... it was like a super quiet pulsating sound that ramps upward in frequency and then holds. If it sounded anything like a normal distorted sound, I would try adjustments.

Exactly!

Both pots work properly. The volume pot for the speech is maxed out.

That was never a problem. Board passes all tests... it's just this speech phoneme getting triggered on power-up. I've proven to myself this groaning sound is coming from speech circuit because it only responds to speech volume pot, and not the sound volume pot.

Both volume pots work... I turned up speech a bit, which is max, and put the background sound down a little. They seem to work/sound good when I turn them up/down.

I'm actually looking at U16 chip, which has been changed at some point. It's the 74LS04 inverter where these sound triggers come into the board. Keeping in mind that the problem also occurs when the driver is unplugged, I'm wondering if this chip is flaking out and passing noise internally from 5 volts to an output... of course that doesn't explain the issue that happens when I put C22 back into circuit.

Exactly my thoughts. I don't think it's RP1 or RP2, especially since the solder is untouched and original. Like you said, once it's powered up, everything works correctly. If I set the DIP switches to turn off attract mode, then flip game on/off quickly enough, I can trigger the problem and it should continue groaning indefinitely as long as I don't start a game. However, I'll need a new troubleshooting strategy first.

I'll be working 12-hour days at the county fair until Sunday so I will just pop in here occasionally to see what's posted. Otherwise, I will not be working on my machine until next week. Which sucks for me, because I finally got my Docent kit for the double-edge connectors. (This sound issue happens when Driver board is completely unplugged, so it's not any of those connections. And the connector for the sound board has already been re-pinned.)

My settings were close to where they are now, before I touched them. Maybe ⅛ turn down on sound and ⅛ turn up on speech before it maxed out. The main cabinet pot is set on the low end, otherwise everything is too loud... and the amp hums on that high end... assumed that was normal.

I agree and made that bet too.

Today I incrementally added capacitance to C22... first 100 pF and I had to turn up frequency of speech circuit on R6 by ¾ turn cw. Added another 220 pF for a total of 320 pF and had to turn R6 cw another few turns. So now with ~300 pF on C22 as specified on schematic, the sound & speech is sounding normal again.

That's not the end of the story. After powering up 20+ times without issue, I was going to post moderate success here, but decided to give it a little more time. Well, the problem came back... brand new Molex edge finger pins, brand new cabinet caps, brand new sound board caps, brand new caps on S & S power supply, and a cap in place for the missing C22...

... what could possibly be next? Out of ideas again.

Yes.

All pots on the speech circuit are working though. They adjust what they are supposed to adjust and hold their setting.

Decided to get this board under 10x magnification especially since my eyes don't work like they used to.

Found some mystery corrosion on two of the legs of the test button. It's weird... the only corrosion on entire board, but I'm fairly certain the test button has nothing to do with the issue...

test buttontest button

Overall, the board looks pretty good. Ignore C22; it's working but it's temporary until I order a new one.

A6 frontA6 rear

But on closer inspection, you can see that U12, U16, and U17 have all been changed. It looks like solder flow to the top traces of the board are not that great... either not enough solder or the joints have cracked.

U12U12U16U16U17U17

U12 feeds signals directly into the speech chip, and U16/17 take the triggers straight into the board and over to the processor. They all need to get fixed, but would like to know which one is causing the issue... I'll probably fix one at a time just to see when it resolves.

The question now is to reflow solder or remove & socket? Leaning towards reflow - less risky and presumably none of these chips need changing.

schematic

EDIT: U12 reflowed top and bottom... wait & see.

As stated in previous post, U12 was reflowed front and back. The problem came back but at a higher pitch.

So then I reflowed U16 & U17, which should cover everything identified with cracked or missing solder.

No good. Problem is still there... back to same tone and pitch as originally posted. Problem goes away and stays away during normal game play and attract mode. Nothing has changed.

Yes, good point. But is there any specific reason to change it again? It would have to be intermittently creating/sending a signal only during power-up, and work perfectly fine during all other times. I'd like to be able to troubleshoot ideas somehow since I don't have any 7407 chips on hand.

If you're talking about what I did a couple weeks ago, honestly, I've done so many things I cannot remember... it was probably 47 or 470 µF

Yes. There are literally no electrolytic caps left to change in this machine. Not to mention the addition of electrolytics across the slingshot coils as per Gottlieb service bulletin.

We have beaten the capacitor issue to death... like stated previously, I think if caused by a capacitor the issue would be more common. But I've been wrong before.

No. While troubleshooting an unrelated issue the other night, I noticed my 5 volts had drifted down from 5.1 to something slightly under ~5. I have a new pot on the power supply and it took quite a few turns to get it back up to 5.1 so that was slightly concerning - although I may have previously had it set to 5.05 volts... I don't recall.

But no, the voltage has absolutely no effect on speech sound. Whenever the problem occurs, it's the same tone as per the YouTube video in the first post. So my guess is the spike, transient, or errant signal is always coming in on the same chip pin. I wonder if there's a way to manually trip each line on the speech chip to see if i can duplicate the same erroneous phoneme.

Hmmm... there are white bulbs that flash randomly and those are the flasher type light bulbs. There are also plain red bulbs that flash sequentially like a marquee in the outer box that are driven by a small flasher board. Which ones are you referring to?

I went back and watched my video again. I think the sound dropping out is just something with the video's audio. In person, it's that same sound but it's steady.

Yes, all true... but the vast majority of incidents 99%+ are the same phoneme. Rarely a hiss, and I actually have not heard the hiss in a long time. Changing the phoneme required a capacitance change, which also affected the clock frequency. To me it seems like if it's one phenome, then it may be a defective logic chip that is passing a transient on power up. Again, I'm grasping.

This is good stuff... going to go read it now.

Attract mode on this game is all from the speech side, AFAIK. Since setting attract to 10 seconds, I constantly hear "throw me a sacrifice", etc. The "add credit" sound also resets and removes the errant phoneme, but not sure if credit tone is from the sound or speech side.

Not really sure if it's considered a repeat or simply stuck on. My understanding is that a combination of triggers creates the speech, but do those triggers pulse on for the same length of time or do the pulses stay on to cause the corresponding phoneme to stay on?

For sure, and since closely examining the board's solder yesterday, am convinced they're factory original, which is super-weird.

All great questions. Need a strategy to proceed.

When this problem occurs, these are the only things that will stop it...

• attract mode kicks in, if attract enabled
• add a credit
• start a game
• turn off the machine

If I were to disable attract mode, then this errant phoneme would continue indefinitely or until one of the other actions take place. When attract mode is set to 2 minutes, the errant phoneme continues for 2 minutes. When attract mode is set to 10 seconds, the phoneme continues for 10 seconds... it continues until the attract sounds start. EDIT: attract mode was ignored today... I had to start a game to get it to stop.

At one point a month or two ago, I don't remember what I did or was doing, but the errant phoneme was stopping all by itself fairly quickly after it started. This was temporary, like only for one day it was like that.

It's the only thing in the document that mentions a "stuck" phoneme. After reading about how this chip generates 64 different phonemes, it's really curious how mine is always triggering or getting stuck on one.

I need to absorb this information to understand better...

Screen Shot 2021-09-01 at 2.15.46 PM (resized).png

Screen Shot 2021-09-01 at 2.15.31 PM (resized).png

So confusing... the quoted section is talking about the SPEECH-PAC™ "Load Line" ... it's entirely unclear how we go from the SC-01 chip data-sheet to a complete stand alone circuit called Speech-Pac in this document. And since the A6 only uses the SC-01 chip, I'm not sure how relevant the pages dealing with Speech-Pac are to this.

Page 11 talks about a "figure 2" schematic but the circuits on page 10 are labeled figures 6, 7, 8, and 9 and contain a SC-01A, which is a totally different chip. The description mentions edge connector J1, which is not shown on any of the circuits. I think this PDF was cobbled together from various bits and pieces, and it's missing something critical.

The "stuck phoneme" is a huge clue but without the relevant information about Speech-Pac back to SC-01, not SC-01A, I don't know what to make of it.
I found another PDF online for the SC-01 and it's the same but stops on page 9 - only contains SC-01 data-sheet and nothing about Speech-Pac.

So confusing... the quoted section is talking about the SPEECH-PAC™ "Load Line" ... it's entirely unclear how we go from the SC-01 chip data-sheet to a complete stand alone circuit called Speech-Pac in this document. And since the A6 only uses the SC-01 chip, I'm not sure how relevant the pages dealing with Speech-Pac are to this.

Page 11 talks about a "figure 2" schematic but the circuits on page 10 are labeled figures 6, 7, 8, and 9 and contain a SC-01A, which is a totally different chip. The description mentions edge connector J1, which is not shown on any of the circuits. I think this PDF was cobbled together from various bits and pieces, and it's missing something critical.

The "stuck phoneme" is a huge clue but without the relevant information about Speech-Pac back to SC-01, not SC-01A, I don't know what to make of it.

I found another PDF online for the SC-01 and it's the same but stops on page 9 - only contains SC-01 data-sheet and nothing about Speech-Pac.

It's a steady and constant phoneme tone. The random flashers have no audible effect.

I see it now.

To make sense of their "stuck phoneme" scenario, we'd have to compare Speech-Pac to the A6 schematic... it's more tedious than my brain can handle today... I will have to revisit. Thank you.

And how that all works with the driver board unplugged? The issue also occurs with the driver board unplugged. In other words, unplugging the driver board does not cause this issue, nor prevent this issue... it seems to be isolated to the sound board, unless it needs a signal from the MPU that never gets there. But nothing like that is connected...

A6-P1

1: +12 VDC
2: S16
3: -12 VDC
4: S32
5: +5 VDC
6: Gnd
7: Audio Out
8: S1
9: S2
10: +30 VDC
11: S4
12: S8

If it exists, it somehow has to be part of S1-S32. Otherwise, I don't know where... the other pins are just various voltages. Where on MPU drawing are you seeing this?

BTW, the attract mode did NOT kill the sound today. I don't know if this has to do with attract being set to 10 seconds or what, but back when attract was 2-minutes, for a fact attract mode was killing it.

Here's a video from today...

My finger is interfering with the audio output signal.... then I'm checking for hot chips... none.

Screen Shot 2021-09-01 at 4.54.05 PM (resized).png

That does not look right at all... based on the title lacking an "A" and the reset going through display boards ... I think this is strictly 80B. For 80B, the S & S board was completely different than S & S boards in 80 (Volcano) and 80A (Caveman) games.

Yes, stuck. Everything pretty much the same where it started, except I have a 320 pF cap in C22. As recommended by you, I had to make some big adjustments. I cranked frequency way up about 4 turns to accommodate having C22 in place.

• All electrolytic caps on entire machine changed, including new 12,000 µF for C1
• 320 pF ceramic cap in C22 (and cranked freq up to normal sound to accommodate)
• New molex finger pins on A6 edge connector
• U12, U16, and U17 are not original and I reflowed missing/cracked solder front and back
• New 110 VAC line filter in cabinet

The problem is the same but for the attract mode not making it stop now. Same tone (phoneme) as before.

I suspect maybe U12, U16, or U17 but don't want to replace unless I can verify somehow.

Thank you... the game is playable although this last issue is very annoying. Eventually, I'll figure it out and we'll all learn something.

I discovered the chip is a SC-01A, which I thought was not exactly the same as SC-01; maybe I am mistaken. I popped it out of U14 socket and cleaned the pins. Made no difference although the errant phoneme tone changed into something else this time.

From the Caveman manual, no idea what "not used" is supposed to mean! LOL ...

A6 Caveman

Maybe. The resistor is measuring at 3.25 kΩ (within 2%) and the C3 cap was already changed (Chineseum from Marco). Wondering how close the timing is on that and if cap is slightly out of whack. Then again, I had the same issue with the old cap in place too.

I'd have to remove diode to test it properly since resistor is shorted across it. What's weird is that I was not expecting to read same resistance across resistor swapping the leads since a diode is shorted across it. 3.25 kΩ in both directions. So then I used diode mode to measure CR1 and see 0.59 in one direction and 0.89 in the other... so CR1 is probably ok.

Exactly. I tried that and it works. Everything goes silent when I hit pin 40 on U3 to ground, and then normal attract sounds start up.

So maybe time to look closer at U1 since it's also part of this reset circuit.

Looking at U1 (7414) and doing the DMM diode test mode with red lead on pin 7 (Gnd), and ignoring pin 14 (+5 V)...

I get about 0.65 - 0.67 on every pin except 1 and 8.
Pin 1 is 0.78 and pin 8 is 0.55

Pin 1 is an input of a gate in the reset circuit.

Not entirely sure if this is significant or if the chip needs to be removed to be tested more properly.

Pin 7 on SC-01 comes from U12 and that was mentioned yesterday as one of three chips with bad solder that I reflowed front and back.

I will check the other components you mention. Thank you.

I do not see C17 in the bill of materials or schematics. Remember, my Volcano is using a version 3 sound & speech board from a Caveman.

Which pull-up resistor? On U12?

I'll have to get a 7407 chip first. Is there a simple test or a setup where I can verify this chip could be the root cause?

Thank you!

R10

Screen Shot 2021-09-02 at 12.07.36 PM (resized).png

Ok thanks. Solid advice. I will get some chips on hand and do that.

Does pull-up R10 need to be removed to be measured accurately? It's rated 1.5 kΩ (brown-green-red) but in circuit it's measuring 600 Ω

I lifted one leg. It's measuring good. 1.480 kΩ

No. I heard those are pretty rare and impossible to find.

I ended up removing U12 and installing a socket. I managed to get it done without destroying anything, and the board is still functional. U12 is also showing good as per DMM in diode test mode. I did not test machine long enough, but I fully expect that the issue will reveal itself again.

EDIT: Problem on last two power ups. Phoneme is now deeper in tone, probably since reflowing the solder.

Great question! I was thinking the same.

Exactly! Mine was already socketed... so I pulled it out last night and polished up the legs.

Week of April 5th, 1981

So the chip is likely original, since it predates both my Volcano game (#667 - Sept. 1981) and the Caveman game (#PV810 - Sept. 1982) this S & S board was taken from. Totally makes sense since parts are manufactured before they are assembled.

SC01A

I've been following. Hopefully they got the variable frequency issues resolved. Otherwise, I am hoping I do not need one except as a spare.

I'm in no hurry. It's basically $85 plus shipping. So far, I don't yet believe the sound problem being discussed here has anything to do with the SC-01.

Putting together a GPE parts order now. While I'm at it, are there specific parts on the S & S board that commonly go bad I should look at buying spares for?

EDIT: Basically, ordered a little bit of everything for sound board that I didn't already have on hand including a new 330 pF cap for C22 and a 100 volt 0.1 µF cap for C33. Hoping the new 7407 for U12 takes care of it though.

How/where did you find that? Are the Gottlieb On Target newsletters archived on PinWiki in some organized fashion someplace?

EDIT: Found some more of those here

More Sound & Speech here

And here

The September 1981 technical newsletter is already talking about sound & speech board version B-20887-3. Volcano was introduced in that same month/year so having this model board is appropriate, despite being salvaged from a Caveman.

UPDATE:

So the problem has been quiet for last few days despite no additional work or fixes. It also does this issue on power down but since the power fades down pretty quickly, it's a short burst.

At this point, I'm just waiting for my GPE order so I can replace U12 and see what happens in the long term.

GPE order arrived today. This is going to get attacked incrementally so we will know which part was the trouble.

• brand new 7407 inserted into U12,
• 330 pF, 50 V, multilayer CMD cap into C22,
• and 100 V, 0.1 µF CMD cap installed into C33

Although problem seems to be less frequent over last week or so, even after replacing U12 today, the issue remains! I really thought it could be the 7407.

Now that I have practically a full set of replacement parts for the whole board, I'm taking suggestions on which component gets replaced next.

Voice Circuit

Let's look at R10 again.

It's supposed to be a 1.5 kΩ and it's good. But in the circuit, it measures 600 Ω... why? Because it's in parallel with a 1000 Ω resistor at pins 16-9 in DIP RP1. 1500 Ω in parallel with 1000 Ω is exactly 600 Ω.

But according to all schematics on all three versions of this board, RP1 is supposed to be 2.2 kΩ. Let's ignore the physical evidence that RP1 and RP2 are factory original for a minute. 2200 Ω in parallel with 1500 Ω is 892 Ω

892 Ω as per schematic vs 600 Ω as per my board. Could this be it? 600 Ω is not great enough to consistently hold the signal low on U12 pins 2, 10, & 12?

To test out this idea, R10 could be changed without touching the RP1 DIP package.

Replacing R10 with something around 8300 Ω will bring the effective resistance value at U12 up to 892 Ω...

My configuration:

RP1: 1000 Ω
R10: 1500 Ω
in parallel at U12: 600 Ω

As per all schematics of all versions:

RP1: 2200 Ω
R10: 1500 Ω
in parallel at U12: 892 Ω

Proposed new R10 value on my board:

RP1: 1000 Ω
R10: ~8300 Ω
in parallel at U12: ~892 Ω

I'm going to try a 10 kΩ, which would put effective resistance at U12 at ~909 Ω, which should be close enough (1%) to 892 Ω for the purpose of this test. EDIT: installed 10 kΩ and measuring 908.8 Ω across R10 in circuit.

Thank you. Yes, I purchased a new zener for CR2 and will swap that next if needed. I am measuring 9 volts into pin 1 as expected.

Meanwhile, so far so good with the 10 kΩ resistor at R10. Will have to wait & see now.

The R10 idea did not solve it, but I left the 10 kΩ resistor in place as that makes the effective circuit resistance correct as per drawing.

I swapped out CR2 as suggested and it's "wait & see" again...

Still no good.

EDIT: Let's add C27 to the list of failed attempts.

I'd have to revert R10 back to 1500 Ω if I do anything like that. Not really into idea of damaging board even though it's reversible.

Based on everything I've learned recently about SC-01A, none of those DIP resistors should be doing anything until the chip's strobe goes high, except for the last DIP resistor at pins 16 to 9, which is in parallel to the pull-up resistor R10. By changing R10 from 1.5 to 10 kΩ, I effectively already did what you suggest. R10, soldered on PCB, is presently measuring within 1% of what would be measured if RP1 was 2.2 kΩ

Like Robotworkshop previously explained, the inputs to SC-01A would be ignored until strobe pin goes high.

My next move is C16 ... no idea.

And that's a good point. Just can't comprehend why the factory would use these DIPs instead of the ones on the drawings.

Replaced C16, C40 (again), and C36 (again) - no good, no good, no good.

Oh, yes... this is an excellent suggestion... I forgot about the reset. I also have 50 new CR1 diodes (1N4148)... I don't exactly know why I ordered 50 but they were only a dollar ... I might replace CR1 before doing anything else. Maybe if CR1 is flaky... it's intermittently bypassing the resistor and giving a reset too soon?

I also have a new 6502 CPU from this order, but this is my last resort.

• Replaced CR1 - no good.

• Replaced C3 again - no good.

• Jumped another cap in parallel with C3 doubling its capacitance - no good, but if I'm not imagining it, this made the problem somewhat easier to reproduce.

Maybe I should replace U1 (7414) next?

Looking at this more closely. If the issue is the pin 7 strobe on the SC-01A, and that requires three lines from U12 to all go high in order to activate speech...

• pin U12-2 (from U25-10)
• pin U12-10 (from U10-4 or U9-13)
• pin U12-12 (from U3-3, which goes through U25-8)

I don't know the sequence of signals on power-up so I am just guessing. All three are not supposed to be high on power-up, but how many are high immediately? Is it 1 of three, 2 of three, or none? If 2 of 3 are high, then the the third going high is the problem.

However, if U12-10 is high, then a transient hitting U25 is potentially going to make U12-2 and U12-12 high. So I'm leaning towards U25 next, as this one chip covers ⅔ of the strobe activation logic.

Thoughts?

EDIT: And do any of these stay high? Does the strobe stay high? I guess I need a micro-clip for my probe.

U25 socketed and replaced. No good.

I think U10 is next...

Screen Shot 2021-09-10 at 6.16.04 PM (resized).png

Without having to dig back through the posts, here's probably the most relevant part of the schematic with replaced parts marked.

partial schematic with replaced parts

Here's a weird side-effect of my last change. I socketed and replaced U25. Then I noticed attract mode wouldn't start... then I started a game... NO SOUND! Weird... reboot and all sound is working fine. Sometimes boots without any sound - maybe 50/50.

Then I put back the original 7404 in U25, but sometimes boots without any sound too. I found a third 7404 chip and so far it's more reliable. So it seems like a new problem has emerged that I am hoping just has to do with these old NOS 7404 chips I have on hand.

•  Can a 74LS04 be used in place of the 7404 in U25? EDIT: board will not produce any sound when I tried my older 74LS04. I inserted a brand new Chineseum knockoff 74HC04 and that one is working without issue so far. WAIT & SEE... maybe this was the root problem.

•  Can the WDC65C02 be used in place of 6502 in U3? If so, does it also need the pin 36 modification that is required for system 80 MPU boards?

I clipped my logic probe onto the strobe line (pin 7) of SC-01A and watched it. Probe in TTL mode is shows this line staying low... but when the board is speaking, you can see the orange pulse light on the probe blink one time for each phoneme called. I could not reproduce the issue while doing this so I couldn't see how the continuous errant tone is triggered.

However, while switching the machine on & off, I could sometimes see the orange light on the probe flash exactly when I clicked the switch, so definitely a transient is getting through to the strobe line, without a doubt. Just not sure if this occasional transient is normal or enough to cause an issue.

(I wonder if an LED can be installed into this strobe line as a permanent troubleshooting aid without causing new issues?) EDIT: That did not work for some reason... probably because I have no idea what voltage level this strobe is operating at.

With that in mind, my strategy is to continue working outward from the strobe line, and U10 is next...

U10 socketed and replaced C12 on this chip. Also went back and replaced C44 on U25. For the heck of it, C5 and C15 looked beat up so replaced them too. All the electrolytic caps on this entire board have been replaced twice in the last two months. First with Chinese from Marco, and subsequently from GPE. So I think I'm done randomly throwing electrolytic caps at this machine.

More wait and see, which is painful because this problem can be elusive. Will disappear for a day or two and then pop back up...

I am working my way outwards from the strobe line (pin 7) on SC-01A.

Here's the latest scorecard of what's been replaced so far...

1. New electrolytic caps on A6 board
2. Grounds verified ad-nauseam
3. New molex pins in A6 connector
4. All main electrolytic caps verified as replaced
5. Corrected neutral and hot lines swapped
6. New 110 VAC line filter
7. Toggled all DIP switches - verified working
8. Replaced all electrolytic caps in cabinet - again
9. Replaced all electrolytic caps on sound & speech power supply - again
10. Temporary cap installed in C22 (previously missing) - had to crank up frequency pot to compensate
11. Reflowed solder on U12, U16, and U17
12. Pulled and polished legs of SC-01A
13. U12 socketed and replaced
14. C22 replaced permanently
15. C33 replaced with higher voltage value
16. R10 replaced with larger value to compensate for lower value at RP1
17. CR2 replaced
18. C27 replaced
19. C16, C40 (again), and C36 (again) replaced
20. CR1 replaced
21. C3 replaced - again
22. U25 socketed and replaced with NOS 7404
23. 7404 in U25 changed 2 more times (failure to produce sound issue)
24. New 74HC04 in U25 - booting with sound reliably now
25. U10 socketed and replaced as well as C12, C44, C5, & C15

replaced parts

Thank you. That's good to know. From what I'm learning about how the speech chip is activated, you should not be experiencing that either.

Most of the time I've have zero groan at power-up and shut-down. It's only happening occasionally on both power-up and shut-down. I only assume it has the same root cause since both coincide exactly with switch click. Usually, if there's a power-down groan, I will have a power-up groan within the next switch cycle or two. Sometimes it just happens walking up to machine and sometimes it's hard to reproduce.... repeated switch clicks in a row.

As I worked through these components over the last several weeks, the issue has been becoming less frequent and harder to reproduce, but not gone. I don't know if that's a coincidence as it also appeared to come & go throughout the summer.

Right now, since replacing U10, I have not had one incident since yesterday. Fingers crossed and need to give it some more time.

That is interesting... this happens every time?

Mine powers off silently. The power-off groan is an intermittent thing, like the power-on groan.

Just imagine that power-down sound continuing indefinitely, and that's what I'm hearing on power-up too.

I have been, which is why I think you should not be hearing anything after power-down switch-click either.

Same exact thing that's happening on power-up... switch is clicked => a transient spike is coming from the switch.

That's just the physics of mechanically making/breaking an electrical current with any sort of load attached. Voltage spikes. Good circuitry and capacitors should filter most of that out. In this case, I believe one or more of the 40-yr-old logic chips are passing random small transient noise through their outputs. This might explain why the problem becomes less frequent as more chips & caps are replaced. 40-yr-old chips might also explain why a few others here have machines that exhibit something similar on power-down.

A couple of parts ago, I could see a transient pulse on the strobe line that activates the speech chip using my logic probe. The pulse was exactly in synch with the switch-click. I could not replicate the problem at that time, but that may have simply been because the transient pulse was not long enough or another fault condition was not met.

UPDATE: So far so good, and I have been clicking the machine on/off frequently today.

At this point I'm fairly certain I finally solved both the power-up and shut-down groans by replacing U10 (74LS02). This is one of two chips that directly feed the inputs to U12, the chip which generates the strobe for the speech chip.

I will leave this thread marked un-solved for several more days of testing, just to be sure.

Still holding strong!

I greatly appreciate the encouragement and support of everyone here.

I will give it more time and post updates as needed.

FWIW, mine groaned, hissed, bweeeeeeeed, whooshed, and burped on shut-down occasionally, right up until I replaced U10.

I must have cycled power a hundred times over the last couple of days and not one tone on power-up or shut-down since the last part was replaced. In my opinion, this demonstrates that these errant tones on power cycling are not part of proper operation as designed.

I believe both the power-up and shut-down groans are both caused by tired chips and spikes. Just tired, not defective, as the sound & speech board worked perfectly fine during normal game operation. Prime example: U25 when replaced with a couple good-testing NOS 7404 chips, A6 board would not boot at all (no sound/speech) about half the time, and when it did boot, it was perfectly fine during normal game operation. The age/condition of these particular chips seem to be most critical and apparent during power cycling, not game play.

I plan on leaving them up.

Still holding good!

Attract mode set to 10 seconds. Video shows me turning it on/off several times without any weird sounds on power-up or shut-down. I even shut it down a couple times during sound play. (I have my doors/windows open so you can hear the wind/trees and traffic noise in the background... there is no hiss, just windy outside.)

Given the history, I am still going to wait a few more days before declaring victory.

Totally agree.

I normally have mine at 2 minutes, but found that 10 secs is great for testing, as the sound starts 10 secs after power-up, which is 5 seconds after the MPU boots.

One good thing about 10-sec attract mode is that you'll never walk away accidentally leaving machine turned on.

No surprise there. Caps are cheap and it never hurts to replace them, but capacitors are not a magic bullet. Sometimes focusing on them too much sidesteps real issues and more serious troubleshooting.

When does the issue happen for you?

Put a logic probe on pin 7 of SC-01 while speech is happening. Signal should stay low and each phoneme will be seen as a brief pulse. For my issue, I could see extra pulses when I clicked the power switch. Maybe you will see your audio glitches as extra pulses?

If the pitch is fast, maybe the frequency pot on the speech circuit has completely failed or flaking out? Pull the board and measure resistance while turning the pot.

The pot number depends on the version of the A6 board. If it's v3 like mine, then for adjusting speech frequency, it would be pot R6 (10 kΩ). If turning R6 has no effect on pitch or speed of speech, then this pot would likely be bad.