I just got my Flash running - had a bad IC (7410) on the MPU that was keeping me from booting. Now I noticed that the sound board test button does what yours does - just does one tone. I can run the diagnostics and get the different sound effects, but how did you get your test button to work??
It's 40 degrees in the garage so my troubleshooting might have to wait until it warms up a bit here!