But, if you're a stickler for originality, you can also order replacement 2N4401s, too ( RS Components, RTBB, PSPA, Mr Pinball).Īnd that turned out to be it. I love the PN100 transistors as you can keep a bunch of them in your toolbox and they replace a number of other NPN transistor types. I replaced it with a PN100 transistor ( Jaycar). Some idiot had replaced this transistor with the wrong type! The outputs of NPN and PNP type transistors are basically reversed, so the coil was being driven high constantly instead of being low constantly. However, what was installed was a 2N4403 (PNP type). This is supposed to be a 2N4401 transistor (NPN type). I took a closer look at the transistor and discovered what the problem was. Everything had been replaced in this section except for the predriver transistor at Q23. The problem had to be downstream.Īfter verifying the connectors and wiring were all intact, I looked again at the driving transistors. So, it looked like all of the circuitry above the driving transistors was working properly. Even after swapping the chips at 1J and 2J (luckily whoever replaced them previously had socketed them), there was no change. Using my logic probe, I could see that the output was pulsing properly whenever the coil was activated in test mode. In particular, Q30 is driven by 2J, the output of which is at pin 3. The transistors are driven by two 7406 integrated circuits ( Jaycar, RTBB) located at 2J and 1J just above the driving transistors. The new transistor tested OK, so I started to suspect prior repairs to the board. Just to be safe, I replaced it with another TIP102. Testing it using diode test on my meter gave suspect results which were "off" when compared to the other transistors nearby. This transistor had been replaced with a TIP102 ( RS Components, RTBB, PSPA, Mr Pinball), which is the recommended replacement, but you can also use another TIP122 if you wish ( RS Components, Jaycar, RTBB). The primary driving transistors are TIP122s and the right drop targets are driven by Q30 on the CPU board. The customer advised that he had replaced the driving transistor already, as well as the associated resistor. There was nothing wrong with the coil itself as the coil was the correct type, measured the correct resistance, and was wired correctly. However, closing the door and re-energising the coils locked them in the up position again. Opening the door cut the high voltages to the coils, and allowed the drop targets to fall normally. It became obvious that this was because the reset coil was locked on, and keeping the targets pushed up. The three drop targets on the right of the playfield could not be knocked down. This was one of two original problems that the customer wanted fixed to start with. However, I performed some interesting repairs on this machine which warranted writing some of them up. So, I won't bother with the standard descriptions of the machine's condition or nitpick the defects. I just needed to get it back up and playing. My customer had pulled the machine out of his warehouse for the first time in years and wanted it to brought back to working condition. There was limited disassembly performed and pictures were only taken of the issues I was tasked with fixing. This will be a shorter blog post as this was not a full restoration by any stretch. While a lot of people prefer the more modern music themed games such as AC/DC or Aerosmith or Metallica, I still prefer the older games, so Guns N' Roses scratches that rock theme itch perfectly. One of the few rock music machines from the 1990s, it is a really cool game with some interesting design decisions incorporated into it. Many people consider Guns N' Roses (Data East, 1994) to be one of Data East's best pinball machines.
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