Unfortunately, one of the problems with owning classic arcade games is the fact that they will eventually quit working and need repair.  Such is the case with poor Dig Dug.  For the last few weeks, the game has been playing fine and then suddenly going to a scrambled screen of graphics.  It became progressively worse and finally was just the scrambled screen when powered on.  Needless to say, I wasn’t able to get any pictures of the scrambled screen.

My first step was to start checking the voltages going to the game circuit board.  Everything checked out fine except the 5v test point was a little high at 5.4 volts.  I dialed that back down to an acceptable 5.1v range using a pot on the A/R II board (Audio Regulator PCB).  I started talking to fellow collectors about my problem and one requested a picture of the scrambled screen to try and help diagnose the problem.

As luck would have it, I fired up the game to take the requested pictures and immediately smelled smoke.  I quickly went to the back of the machine, powered it off and saw a stream of smoke rising from the game circuit board.  Most of the resistors in the circled area are fried (click for a larger picture):

Fried Resistors

I’m told this is what happened; the edge connector was not making sufficient contact and +5vdc shorted to ground.  This resistor network was the weakest link before smoking resistor R30 on the A/R II board.  Sure enough, I checked and resistor R30 on the A/R II board is fried.  Just for reference, here’s a shot of the A/R II board when it was working.  R30 sits between the 6 and 9 pin connectors (click for a larger picture):

AR II Board

I was also told to check the edge connector on the game board and check for burnt areas. Sure enough there is a small burn near the first finger on the parts side:

Edge Connector Parts Side

I can handle the repairs to the A/R II board but the game board repairs may be above my level of expertise.  I’m going to look for a cheap, working replacement board and send this one out later for repairs just to have a spare around if the need arises.  Until then, Dig Dug will sit in silence while Donkey Kong laughs at him (I hope I didn’t just jinx myself)!