Repair logs are quick summaries of workshop and on-site repairs. If your machine needs a service, 📬 Contact Us to discuss how we can help!
Plenty of fun repairs to get this Doctor Who running at full speed. First problem was an easy one. No action from the right flipper at all. Cabinet switch worked fine, but the coil would not fire. Took a look under the playfield and saw that the BLU/YEL wire had broken off the coil, as well as the power and hold coil windings. This wire is the 50 volt supply from the flipper board, and without it you'll never get any flipper action. This coil had a hard life as the lugs had all broken off at some point, but you can use the eyelets as a convenient solder point as well. Once the wire and windings were reattached, the flipper came back to life.
Error reports indicated failures of some of the opto switches on the mini playfield opto bank. First step is to raise the mini playfield so you can activate the switches in test mode. And this was the first roadblock. The mini playfield would not move up or down at all! We will deal with that a bit later... but to get around this, you can unbolt the gearbox and cam assembly from underneath the mini playfield. Remove them, and you can now move the mini playfield by hand. Just don't drop it on your fingers!
With the switches accessible, I found three out of five were unresponsive. Taking the target bank assembly off the mini playfield gives you access to the opto boards for inspection. The problem with one switch was obvious right away. Broken ORG/GRN wire on the receiver board. Soldered it back on and that switch started working again. Two more to go. These turned out to be dead transmitter optos. You can check these with your phone camera; a glow indicates they are working, no glow indicates they are not. These two were replaced, and all five switches were back in action.
Back to the mini playfield movement issues. The gearbox was rooted. I could move the cam freely by hand, which is a bad sign. I cracked the gearbox open to get a better look. The problem was the gear attached to the main arbour. It was freewheeling on the shaft. A pretty common failure, particularly on Doctor Who. Off to my mate Darren who is a great welder. He silver soldered the gear and spline back onto the shaft. Greased the gears and rebuilt the gearbox. Back in the game, the mini playfield moves up and down really well now.
Last issue (for now!). No sound effects or music at all. Game booted up and made two "bong" sounds. The sound board has its own processor, so the tones tell you its status. Two bongs means the 6264 RAM at U9 has failed. I've seen plenty of cases where a failed RAM will not trigger any unusual messages and will appear to boot normally. However U9 is usually the problem. I removed the chip, installed a socket, and plugged in a new one. Replaced the electrolytic caps at the same time for good measure. Sounds are all playing again!
That's enough excitement for now! Hopefully that keeps this machine going for a very long... time!
