System 11 music intermitant issue

(Topic ID: 231007)

System 11 music intermitant issue


By Platypus

12 days ago



Topic Stats

  • 2 posts
  • 2 Pinsiders participating
  • Latest reply 12 days ago by Hawk007
  • No one calls this topic a favorite

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#1 12 days ago

My 1986 Space Station has worked and played great for a few years now since I had replaced several connectors and other minor board work. Now just as I am about to loan it to a friend for an extended period the music starts cutting out. the music will play for a while and then just stop and start up again later. The call outs don't seem affected.

I am prone to believe that it is a bad connector or bad solder joint. I have looked for anything obvious on the audio board to no avail. I have been able to track other problems down on my other boards but I am new to the Audio board. I am not sure of the roles that the sound roms U21 and U22 (on the CPU) have or the music rom U4 on the audio board?

When I turn the game on I get a single tone which should indicate no problems with the roms. When I press SW1 on the CPU one callout repeats (condition green) no rings. This suggests normal functioning

Can anybody offer any tips on where to look or what to try?

#2 12 days ago

First off check for acid damage or prior acid damage. Number 1 cause of this.

Next major villain is this system is the aging connectors and headers specifically the ribbon cable. Remove and reseat about 10 times and it 'should' clean off the terminals and pins and make a good connection. New ones are also good, especially if the old ones 'feel' loose.

Checking power should be done first of course if no acid damage ever. Board has +5,+12 unreg and -12 unreg. Not uncommon to see 4.91-5.02 , +14 and -14 volts there. If not within spec power supply work is required.
If cable is good and power is good check headers on the ribbon cable to see if there is any pins missing. Seen one or two pins gone and cause this.

As you were just in there so to speak I am prone to think poor ribbon connection or missing ribbon cable pin.

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