|Smart Ball Skeeball - Audio Circuit Troubleshooting|
|Posted by: AceBHound on Dec 1st, 2011 7:19 PM|
|I had an interesting time last weekend attempting to diagnose the audio circuit on the Smarty skeeball machine. I learned a few things.. first of all they use a BSMT2000 DSP (digital sound processor). This was basically a Texas Instruments 320C15 DSP processor with some special rom code.. that way instead of having an external IC with ROM code on it, the ROM code would be directly burned to the ROM space on the 320C15. Anyway, what was really interesting is this BSMT2000 is used in a lot of pinball and video games, especially the Data East and some Sega/Stern pinball machines.
I had schematics for the Smart Ball but the audio section was different on the actual CPU board in my machine. They used a DAC (digital analog converter) that took a serial data input versus using a DAC that took address inputs. So I basically spent 2 days learning about the ICs used in the audio circuit and trying to figure out how to troubleshoot it.
I found a shorted logic chip that was dragging the clock signal down that ultimately meant no serial data reached the DAC chip. After replacing the logic chip, still no audio.. but my logic probe shows pulsing [data] at the data pin on the DAC now so some progress was made.
Found a supplier for the power amp and preamp and I'm really hoping one of those is the remaining culprit. With the BSMT2000 in this Smart Ball, it must put out some decent sound.. they wouldn't have crappy beep sounds with that kind of audio power in it =) I'll have to post a video or picture of the machine sometime soon. Definitely if I get the audio working on it.. and probably a repair log too. You don't see much information on these machines and I've had a chance to learn some about them so why not put it out there for others?