T2 arcade sound problem - Page 1
Forum section: electronics / beginners

author: Eastbayraym
author_rank: Newbie
timestamp: October 13, 2021, 04:13:21 pm
content: I’m having issues with my terminator 2 arcadeEverything works great except the sound bites (let’s go, awesome, I’ll be back,etc)If u pull the trigger without credits I think it says no way or something but mine cycles all the sound bitesBasically says everythingI have already replaced the caps, checked the wiring, and verified the romsAny help would be appreciated thanks

author: Manul
author_rank: Super Contributor
timestamp: October 13, 2021, 05:48:10 pm
content: Have you found schematics? There is probably a separate board for sound synthesis and sample playback. Problem could be with some control logic or bus. It could be hard to find without looking deep into how it works.

author: james_s
author_rank: Super Contributor
timestamp: October 13, 2021, 06:30:52 pm
content: Terminator 2 does have a separate sound board, it looks like it's very similar if not identical to the one used in Mortal Kombat, NBA Jam and other Midway games of the era. The first thing I'd check is the ribbon cable between the main board and sound board. Also in the self test menu there should be a sound test, run through that and see what it's doing. Since music, synthesized sounds and digitized speech comes from the same board it makes me think this could be a fault on the sound board itself. I've seen bad ROMs on a handful of arcade games in the last few years.

author: Eastbayraym
author_rank: Newbie
timestamp: October 13, 2021, 09:47:42 pm
content: It’s a midway Adpcm sound boardRoms are good (checked em on the pc)In test mode sound board tests fineI was told it’s probably something around the oki chipGonna have to do some probingThanks for the help if u have anymore ideas let me knowThing is driving me crazy

author: james_s
author_rank: Super Contributor
timestamp: October 13, 2021, 10:25:50 pm
content: So the sounds all play correctly when running the self test in the setup menu? If that's the case then that's a very strange problem.

author: Eastbayraym
author_rank: Newbie
timestamp: October 14, 2021, 02:06:41 am
content: Well no the sound bites are still offGarbled and wrong or overlappingBut the test comes back as working

author: floobydust
author_rank: Super Contributor
timestamp: October 14, 2021, 04:12:33 am
content: Did you look at this for ideas:https://www.arcaderepair.net/williams-midway-cvsd-adpcm-sound-boards/

author: Eastbayraym
author_rank: Newbie
timestamp: October 14, 2021, 11:46:54 am
content: Yup I did very useful info thanksI’m gonna have to just test everything till I find the problem

author: james_s
author_rank: Super Contributor
timestamp: October 14, 2021, 07:28:03 pm
content: Quote from: Eastbayraym on October 14, 2021, 02:06:41 amOk now I'm confused. If the speech samples are garbled and overlapping then the test is NOT working, the whole goal of the sound test is that each sound trigger plays exactly one sound, and that it is the correct sound for the code being triggered. If any of the sounds are wrong then the test has failed. Obviously the game board has no way of knowing what is actually coming out of the sound board, it is the responsibility of the human to monitor that.

author: floobydust
author_rank: Super Contributor
timestamp: October 14, 2021, 10:22:31 pm
content: I would suspect the CPU or SRAM, it could be where the sample counter is, malfunctioning and driving past the end of the snippet.I can't see another reason to "overplay" a sound snippet and keep cruising through EPROM, missing an EOF marker or something.Mosel 2064 8k x 8 if that's what's on your board?SRAM replacement using 6264looks OKYou'd have to install an IC socket. Some other boards seem to use an ordinary 6264 SRAM.I played T2 constantly when studying for final exams at university. It was a great way to blow off anxiety so you could study for another hour

author: james_s
author_rank: Super Contributor
timestamp: October 14, 2021, 11:39:40 pm
content: Looking at the manual, the schematics while not the greatest resolution are at least nicely laid out and it looks like the speech synthesis has its own CPU, RAM, ROM and glue logic that is all just for the speech. Bad RAM is certainly a possibility, I would also still keep the ROM on the suspect list. I know you tested it but I have seen more than once where an EPROM tested fine in my programmer but failed under real world conditions in the equipment that used it. I have not studied this particular sound board in depth but I have looked into some other older ones and usually it's fairly simple. The code knows where the sound samples are stored in ROM so the start and stop addresses are latched somewhere and then a counter just increments until the values match and it stops.