Not sure if you read my super long thread about my Volcano adventures with the speech portion of my sound & speech board. I know you don't have speech on your version, but I remember mine very occasionally booting up without any sound at all.

Something else you describe that sounds familiar. I would get a random tone on startup that stopped as soon as another sound was triggered.

If you can figure out how that lava sound is triggered, then you can trace out which components may have failed and are triggering the sound when you're not calling for it.

I wish this could be more specific, but maybe reading my thread might give you some ideas about how to troubleshoot your circuit to help narrow it down.

Yes, A6 only has one connector so it stays plugged in. However, I completely removed all Driver board connectors, to eliminate the possibility that my problem was being triggered externally. Game will boot and should have all attract mode sounds... it just will not have any sound triggers.

So what happens after boot-up when you have the card set to 10-second attract mode? Stays silent?

The single-sided connectors could have been re-pinned using the same plastic housings with new Molex pins. Only the Molex pins for the double-sided connectors are obsolete and would require special parts.

The dip switches on the sound board control attract mode, not the MPU... which is why I asked the question - as a means to further your troubleshooting. If attract mode is not working despite DIP settings then it's a problem narrowed down to the sound card.

I noticed my schematics show the SC-01 speech chip as "optional".... so I assume they just left the chip out to make it sound-only version for the European market? Is this the case? BTW - which board version do you have?

I don't know why you were responding to me... that is the exact same troubleshooting suggestion that I made to the OP.

Totally agree. No worries.

That is not the same sound card in my US Volcano. I have the Sound & Speech card. Since my schematics show the SC-01 speech chip as "optional", I had assumed your European version had the same card but without the SC-01.

Do you have the correct schematics to refer to?

I sometimes noticed that on mine too.... however according to the book, machine must be in "Game Over" mode when you do the test.

The OP seems to have a problem with missing scoring sounds that he used to have. AFAIK, I don't believe he's asking about speech.

Mine has that exact same warning tag. I have no idea what the idea was behind this warning, because AFAIK, the Sound & Speech boards for system 80 games are completely interchangeable as long as you use the correct ROM for your game. After all, the System 80 S&S schematics are nearly identical from any manual with a S&S board. And where it's not identical, Gottlieb recommended various changes to make it the same circuit as a rev 3.

My Volcano is using a Sound & Speech board from a Gottlieb Caveman. The Volcano manual (1981 system 80) has the S&S rev 1 schematic and the Caveman manual (1982 system 80A) has the S&S rev 3 schematic. Completely interchangeable.

Based on this Gottlieb tech newsletter from June 1981, I think that warning label was strictly meant for games with sound only, not Volcano.

On Target - June 1981

That being said, and based on the warning label, I don't know how your Volcano can be using the regular sound-only board. Maybe any sound/speech game can be safely downgraded to a sound-only board, but a sound-only game cannot be upgraded with a sound/speech board?

And by Sept. 1981, same month Volcano was released, the Gottlieb newsletter was already describing the various sound & speech circuit modifications that make the board into what's equivalent to a rev 3.

On Target - Sept 1981

As you state, two versions for Volcano... one is "sound/speech" and the other is "sound only".

I have a Volcano with sound/speech and the OP has a Volcano with sound only. However, we both have the same label that says:

"the sound board in this game is not interchangeable with the System 80 sound/speech board. If a sound/speech board is mistakenly installed in this game, it will be damaged."

This label makes absolutely no sense as it is written, at least not for my game, which came with a system 80 sound/speech board (with the A6 power supply in bottom cabinet). Mine is a US game, and based on many physical clues, sound/speech is original.