English Mark Darts-Super 6 Plus II

[herbally]

I've got two of these dart boards, and one seems to work perfectly.  On the other one, the lights on main board don't light, but if I swap that board to the other machine they do.  Based on the troubleshooting guide in the manual I suspect the culprit could be PIA U4, but for the life of me I can't figure out where the peripheral interface board is.  I've even tried swapping what I think to be the coin credit board but the problem remains the same.  Any suggestions?

Thanks in advance!
Herbally

[Ken Layton]

Check the power supply board. It's a well-known major trouble source in these machines.

Also, do a search in this (misc arcade) forum on Arachnid and darts. Lots of helpful threads are already posted including links to manuals.

[herbally]

Thanks Ken!  I actually already read most of the related threads including a lengthy one containing several helpful posts from yourself.  Thanks to those posts I was able to get the partially functional machine with no video/sound working with video and sound, but I didn't see anything specific to the lights on the main circuit board.  The sound issues is a bad connection on the main board, that I haven't fixed yet.  I guess maybe I should just work on making all those connections good before further troubleshooting.  Maybe that will resolve the issue.

[herbally]

So I tested the power supply both in-game and out, and it appears the there is no +12v on pin 5 or pin 7.  I have 11.79v on pin8 (labeled +12).  I tested pin 8 on the working machine and its at 11.72/11.73 so I'm assuming 11.79 is normal.  Also I noticed the heat sink is missing on BR1 on the ps circuit board.  Am I to assume that this is a bridge rectifier which I think I read go out frequently on these units?  Should I also assume that it's faulty, and the cause of the lack of 12+??  Thanks!

[Ken Layton]

Bridge rectifier BR1 is the main raw DC source feeding the +5 volt regulator, the +12 volt monitor regulator and the +12 volt lamp regulator.

If you have no +12 volts at output connector pins 5 and 7 then you have a bad MC7812 voltage regulator. It provides the lamps with +12 volts. This is the small standup regulator with the black heatsink bolted to it.

The other 12 volt regulator is the great big one bolted to the board inside a huge heat sink and it only provides power to the monitor. That one is ok.