I recently acquired Close Encounters machine that I am trying to get in working condition again. It sat in a family members basement for many years after it stopped working one day. This is also my first time working on a pinball machine. I've read Clay's guide (http://www.pinrepair.com/sys1/) to understand what needs to be modified on these sys 1 machines. When I received the machine, I went through all the power train testing as described in the guide. Everything checked out:
-coils all had good resistance
-bridge rectifiers were getting good readings
-power supply board was supplying all the right voltages
-displays were working too, but giving me some weird numbers
-startup didn't seem to work either, since the game over and tilt relays did not click
I replaced the C1 cap with 10,000mfd 35V axial cap. At first I thought I would have to remove the board from the L bracket. I started doing so, but realized I could just cut the existing C1 leads and soldered my new cap to them. I also added the ground wire to the negative side of the C1 cap. However, now I am blowing my 69V fuse. It only blows when I have my power supply A2J1 connection and nothing else on the board. With the board disconnected I am getting the following voltages on A2J1:
Pin 1 or 2 to Pin 3 (ground): 12.86VAC
Pin 4 or 5 to Pin 3: 15.56VAC
Pin 6 or 7 to Pin 3: 36VAC
Pin 6 to Pin 7: 77.4VAC
I also checked all the diodes in forward and reverse:
CR1: 0.480 & OL
CR2: 0.553 & OL
CR3: 0.604 & OL
CR4: 0.572 & OL
CR6: 0.583 & 2.668
CR7: 0.596 & 2.684
CR8: 0.587 & 2.683
CR9: 0.576 & 2.687
A little confused why those last 4 diodes are getting non-OL in reverse. Does this mean the diodes need replacing?
Another theory I had was that when I was attempting to remove the power supply from the L-bracket, I messed up the Q2 transistor isolation. Indeed, the mica insulator was shifted and I noticed plastic bolt insulator has gone missing. I adjusted the mica and temporarily removed the bolt until I could get a replacement insulator, but the fuse still blew. Is there anyway to check the transistor to see if it is properly insulated or causing a short?
Any suggestions would be much appreciated. I know I must be missing something silly. Considering if it may be better just to replace with a Rottendog power supply, but was hoping to give it my best shot first.