 After my World Cup Soccer restoration, I was rearing to go for another. Doctor Who (Bally, 1992), was another machine I had bought at the same time as World Cup Soccer. I had a lot of mixed feelings about Doctor Who as a pinball machine. While I wasn't much of a fan of the TV show or other Doctor Who media, I hadn't played the pinball machine much before and many pinheads insist that it is a really cool game. The mini playfield is the main feature on Doctor Who. It's a section of playfield that rises and sinks to reveal objectives to hit; it is very similar in style to the ball lock area on Jack-Bot (Williams, 1995). Doctor Who definitely looked like more of a technical challenge so I decided to sink my teeth into it and see how far I could get. Initial condition report (click on sections below to view details) Cabinet
Good condition overall.
Above playfield
Average condition overall.
Under playfield
Average condition overall.
Electrical
Good condition overall.
I wanted a challenge and I certainly got what I bargained for! The majority of Doctor Who is easy to take apart. The playfield actually doesn't have much on it apart from a couple of ramps. Take the right ramp off first, followed by the Cliffhanger (upper) ramp. The rest of the playfield components can be taken off in any order you like. Below are a couple of images of the disassembly process. The rubber ring configurations were interesting! A word on working on the mini playfield. If the mini playfield is clean, working properly, and otherwise error-free, then leave it be. Bad things happen when you fiddle with the Time Expander for no reason. If, however, your mini playfield was anything like mine, it'll need a thorough rebuild. There are instructions in the manual that describe how to remove it from the main playfield. These instructions also cover removing specific components from the mini playfield individually.
These instructions are useful, but vague. Every Doctor Who owner who has done work on the mini playfield has therefore resorted to Rich Fazio's fantastic guide on disassembling and repairing the Time Expander mini playfield. This guide is the most comprehensive reference on the Doctor Who mini playfield and covers everything about it in more detail than I could hope to cover here. If you're planning on taking the mini playfield out and are having trouble with the manual's instructions, Faz's guide will make things much clearer. Download a copy here: 
After disassembly, the game went through my standard restoration process to get it playing and looking like new. During the restoration process, I dealt with a number of issues, described below. Raised inserts
The "Hang On" arrow insert was raised slightly and needed to be leveled. Based on my successful experience leveling some inserts during my Getaway restoration, I used the same clamping technique to push the insert back down. This worked well and the insert flattened out nicely. I also did this to the white Transmat insert.
Raised "Hang On" insert with dirt accumulating under the Mylar near it.
Mylar raised and dirty
As a result of the Hang On insert lifting, some dirt and debris had made its way under the Mylar. The only way to deal with this was to remove the dirty Mylar altogether; there is no way to clean the Mylar otherwise. Fiona and I decided to cut out the dirty section of Mylar, which was the section covering the "O" and "Hang On" inserts. As the Mylar was already lifting, it was easy to get a plastic razor blade under it and pry it up to remove. We then used the freeze method to unstick the rest of the Mylar. This process worked really well and we managed to complete the removal without losing any artwork. As we were only cutting a small section of Mylar out, we had to very carefully cut the Mylar out with a sharp blade, being careful not to cut deeply enough to damage the playfield. There are heaps of resources online that explain how to carry out Mylar removal using the freeze method. I have read that the heat removal method is just as effective, but I would personally prefer to spray a short burst of freezing gas onto the playfield instead of expose it to prolonged periods of intense heat. Time Expander cover edges broken
The Time Expander cover (part no. A-15582) is almost always broken at the screw holes, especially on the edges above the standup target. I installed some washers under the screws to give it some stability. The Time Expander cover is now actually being reproduced by Freeplay40, so there are new ones available.
Damage to the Time Expander cover screw hole areas.
Broken slingshot plastics
New slingshot plastics (part no. 31-1681) can be bought from Pinball Center but I elected not to replace the originals on this machine. Pop bumper skirt broken
The pop bumpers on Doctor Who get hammered more than they seem to on other games. They're quite close together and the ball often slams into the topmost one at high speed when shot up the left orbit. This was the first time I'd had to remove a pop bumper assembly from the playfield. In order to do it properly, it was easier to remove the entire playfield from the cabinet and turn it upside-down to access the pop bumpers. This is easy on Doctor Who (and games manufactured prior to 1992) as these playfields use an older pivot playfield support system. They can simply be lifted straight up and out of the cabinet without the need to unlatch them from a slide assembly.
There are plenty of guides available online about how to rebuild pop bumpers, so I won't go into too much detail here. Suffice to say, Vid's guide is a fantastic resource. Parts are readily available from Australian suppliers. I grabbed a new red skirt (part no. 03-6035-4) to replace the broken one. Rebuilding pop bumpers is one of my least favourite repair tasks. They're a pain to extract from the playfield as you need to desolder the lamp leads from underneath the playfield, and then connect them again when you're done. To make this process easier, I now install flexible lamp leads on pop bumper lamps. If the playfield is still in the machine, the bumpers are usually in some hard-to-access spot which makes working on them impossible. But good pop bumpers are important for good gameplay, so it's worth going through the effort. I disassembled the bumper with the broken skirt and replaced it with a new one. Centre post installed between flippers
Why the hell would you install a centre post on a game that wasn't designed for one? For one, it's extra effort to install the post for the operator. Second, the post makes it possible to save the ball more easily. Why would an operator want to extend playtime? It would reduce their income. Even if they wanted to make the game easier, there are plenty of software adjustments that can be made to achieve this. Installing a post is unnecessary.
Even more frustrating was the fact that there was another hole in the playfield near the centre post hole. The post had probably been installed in this hole first, before being moved to the next hole, leaving two holes for me to patch up. Fun! There are plenty of guides on playfield repair online that are well worth a read. In particular, Vid's guide on Pinside is very thorough. Reading articles online has made me think that people overthink these kinds of simple repairs far too much. Repairing simple holes and gouges in the playfield comes down to filling the hole, sanding it down, then painting over the repair. This is the technique I used to fix the holes on Doctor Who. This is what I started with after removing the centre post between the flippers. 
The two holes from the centre post between the flippers before the start of repairs.
Next, I needed to fill the hole. I used Selley's Knead It for this. It is easy to work with until it sets. Fill the hole and pack as much filler in as possible. If you don't fill the hole completely, the filler will be able to move and crack. It doesn't need to be particularly neat as it will be prettied up in the next step. 
Filling the hole with wood filler.
After the filler has set, it's time to sand it down. I would suggest sanding the filler down to a level slightly below the playfield. Don't forget that you will be painting over the top of the filler, as well as applying a clearcoat (if desired). Multiple coats of each can be quite thick, so the lower you sand things down, the more paint and clearcoat you can apply. It helps to mask the surrounding area to avoid marring the undamaged areas of the playfield. 
Sanding the filler so it is flush with the playfield.
Next step is painting. Again, Vid's guide covers this aspect in much better detail than I ever could here. We used Createx Opaque Black in an airbrush, which applied the paint nice and evenly and was a good colour match. 
Repair area after painting and removal of masking tape.
One thing I found particularly interesting was how nicely you could polish the playfield using Novus 2. I used Novus 2 to clean and polish the repair area after using some slightly more aggressive sandpaper to level the wood filler. I was surprised at how nicely you could actually polish the clearcoat up. From the factory, the coat is quite rough, but after some polishing, it shines up like a mirror. Below is what it looked like on an undamaged part of the playfield compared to the repair area. Shiny! If you see your playfield get this shiny when polishing it, exercise caution. You will soon eat through the clearcoat's full thickness and damage the paint.
Finally, I decided to protect the repair area with a final coating. The best option for this is a couple of drops of two-part automotive clearcoat, as this is what is used on the playfield normally. However, this seemed a little excessive for such a tiny wear spot, so I decided to experiment a little. People have suggested a lot of alternative "clearcoats" ranging from varathane to nail polish. Nail polish, eh? Fiona had some spare bottles lying around, so I thought, "why not give it a go?". I brushed it straight on, waited for it to dry, and polished it up. I think it actually turned out quite nicely; the angle of the photo with the oblique light makes it stand out much more than it does from the playing position. Time will tell how it lives up to the ball rolling over it, but I don't expect it to get hammered. 
Centre post hole repair complete!
Star post installed above right outlane
Extraneous star post installed above the right inlane and outlane.
This was an extra star post that wasn't meant to be there. It was installed above and between the right inlane and outlane. Unlike the centre post, I actually understood why this one was installed. The ball would often bounce off the slingshot rubber when it was kicked out of the TARDIS upkicker. This would result in it draining down the right outlane about 20% of the time. This is something that needs fixing, for sure. But all you need to do is adjust the wireform ramp attached to the slingshot and move it left or right! Installing a post is hamfisted and totally unnecessary. There is even a page in the manual that mentions this problem specifically and instructs you on how to adjust the wireform to fix it! I followed the same procedure to fix the hole created by the star post as I did to repair the centre post hole. The repair went pretty much the same way, the only difference being that I needed to paint a small section yellow to match what was on the playfield. Fiona did an excellent colour match on this one using Createx opaque yellow with a dab of opaque red for darkness. Then, some opaque black for the edge. Unfortunately, I forgot to snap an 'after' picture. 
Excerpt from the Doctor Who manual describing how to adjust the wireform ramp.
Ball popper on mini playfield not working
After cleaning the mini playfield, I noticed a loose wire protruding from the black conduit attached to the mini playfield. The wire was purple and one end of it was still securely attached to the coil on the right side of the mini playfield. Specifically, it attached to the coil lug closest to the rear of the mini playfield. It was a very short wire, so I assumed it attached to another component on the mini playfield. After checking out some reference images from someone else's game, I figured out that this wire connected both of the lock coils together. The wire went from the rearmost lug of one coil to the other to connect them. This was a solid purple wire, while the wires attached to the other lugs of the coils were purple with secondary colours. This wire, having broken off, prevented one of the ball poppers from firing. When it was soldered back on, everything worked fine.
Heavy wear to mini playfield and main playfield edges
The mini playfield on Doctor Who gets an absolute pounding from repeated ball impacts. As a result, it is always worn and usually in desperate need of repair and reinforcement. This mini playfield was no different. It was also complemented with other mini playfield protectors after the damage to the front edge was repaired. I go into more detail regarding repairing the mini playfield edge in a separate blog post. Incorrect top flap installed on mini playfield
The previous owner had installed a sheet of thin, flexible metal near the front edge of the mini playfield instead of the correct replacement part (part no. 01-10650). This flap was tarnished and ripped in a couple of places. He had also used some weird glue to adhere it to the playfield, which had yellowed and hardened over time, leaving a horrible residue everywhere. This flap was replaced with a Cliffy protector, which offers more protection than the original factory part.
Mini playfield would not move
At this point, I was happy to finally get the mini playfield installed into the game and working. Hah! No such luck! After cleaning and rebuilding, he mini playfield would not move during gameplay or even in test mode. So, time to get the multimeter out and do some probing...
I had verified that the motor was working with an external power source. This suggested there was something wrong with the power going to the motor from the power driver board. This circuit leads to the motor via a bi-directional motor driver board mounted underneath the playfield (part no. A-15680). Looking at the board, there appeared to be something wrong with the capacitor at C2. Thankfully, this is an easy one to replace as Jaycar have an equivalent part. Pinwiki also has a good description of the problems associated with this capacitor, including the potential loss of 12 volt power for the motor. So, I replaced the capacitor but still did not have any movement at the motor. The LED on the board was on, indicating that the 20 volt supply and ground connection were good. 
The bi-directional motor driver board after replacement of C2.
Next, I checked the mini playfield motor. Perhaps it had shorted to ground or had failed somehow. I tried to check continuity across the motor via the J2 connector from the motor driver board, but got nothing. Weird. Then, I checked continuity directly at the lugs of the motor, where I got a reading of 4.5 ohms. So the motor was fine. But this got me thinking - why was there no reading when I tested continuity from the J2 connector? After all, this was connected to the motor via a connector. And that was the problem. The pins inside the connector had come loose and were not making good contact between male and female terminals. This meant that even when plugged in, power was not passing from the motor driver board to the motor. As a result of this problem, I now replace this connector for the mini playfield motor on every Doctor Who I work on. It is almost always flaky because it has been damaged or the wires have come loose inside of it. Better to replace it and eliminate the problem forever! 
Upgrading the flaky mini playfield motor connector.
Mini playfield mushroom targets were sticking
More mini playfield fun! During reassembly, I had checked that all of the optical switches for the five mushroom targets were working properly. But once the mini playfield was reinstalled, I noticed that hits to one of the targets (part no. 03-8654) would leave it stuck in the "in" position after the ball had bounced away. This caused the opto for that target to stay engaged, causing the game to register multiple target hits. Pushing the mushroom target in manually, I found that the target movement was sticky, as if it was being physically blocked. I pulled everything apart again and looked at the bracket that housed the two opto boards. This bracket (part no. 03-8655) is made of plastic, and over time, the edges can bend inwards towards each other, deforming the bracket. This causes the mushroom target shafts to strike either the opto receiver or transmitter, sometimes getting stuck as a result. This is a case of the bracket simply not being made strong enough at the factory. Ideally, it should have been made out of steel to prevent it from deforming so easily.
The target base plastic piece deforms and compresses under the paper shroud.
The solution I found was to make up some spacers from a strong cardboard tube which I cut to size and pushed into the bracket to keep it rigid. The spacers were placed in between the opto LEDs to prop the edges of the plastic shroud apart. This solved the problem nicely and the target stopped sticking. Later on I discovered that you can actually purchase a 3D printed cover which slots into the original plastic shroud, helping it keep its shape as well as isolating each of the optos. If necessary, you can just buy new brackets (PSPA). 
Spacers (arrowed) were installed between the opto LEDs to give the plastic bracket support.
Some ESCAPE standup targets not working
Intermittent switch issues were causing a number of standup targets to not work during gameplay. However, they would work intermittently in switch test mode. Something was wrong, but was not easily reproducible. The problematic targets were the E, S, C and A on the right side of the playfield (part of the ESCAPE standup target bank). I tested the switch contacts manually with a multimeter and all of the switches appeared to be OK. The big clue for this issue was that the switches were in the same area of the playfield and were part of the same switch matrix column. The yellow wire that connects each of the targets together had come loose between the A and P target switches. It was barely hanging on by a thread of wire, which explained the intermittent switch closures. I missed the break in my first look over everything because the wire was still partially attached. After resoldering it, all of the switches worked properly again. Time Expander insert lamps not working
One issue that seems to be prevalent on many Doctor Whos is cold solder joints on the lamp board in front of the Time Expander under the playfield. This board has a lot of lamps on it in close proximity to one another, which release a lot of heat and contribute to problems with the lamp board and the Time Expander inserts. Some of the lamps on this board were not lighting properly and inspection of the header pins showed that some solder joints were cracked. All I needed to do was reflow solder on the lamp board pins to get all of the lamps working again.
The Time Expander lamp board. Pins on this board are often problematic due to cold solder joints.
Gouges on inside of cabinet
It's pretty common for cabinets to develop gouges as playfield components rub against them when lifting and lowering the playfield. For some reason, these gouges were a bit worse on Doctor Who than on most other games I've seen. All that was needed was a layer of Createx Opaque Black paint to hide them again.
The gouges on the left side were probably due to an incorrect flipper mounting bracket being installed at some previous point in the game's life. The correct part for Doctor Who is a mounting bracket with a trimmed mounting foot on one corner (part no. A-16091-L), so it can sit flush with the cabinet.
Launch ball button damaged
The launch ball button (part no. 20-9663-B-2) was destroyed on this machine, having been smashed into pieces. That's what happens when people are too eager to launch their ball, I guess! The text is printed on a thin piece of plastic. I might try and glue it together eventually, but it was easier to just buy a completely new assembly and whack it in (RTBB, PSPA).
Destroyed launch ball button.
Reassembly I replaced all of the broken lamps and installed fresh black rubbers throughout the machine, including three new black flipper rubbers. I left the broken slingshot plastics on the machine for replacement at a later stage. Doctor Who is also a game that looks great with LEDs, but I did not install any this time. Cliffy protectors are an absolute must on Doctor Who. The mini playfield gets smashed by balls and this is why it is usually so damaged. Cliffy makes three protectors for the mini playfield and I installed all of them on this game. They help cover up repair work and protect the game in the future. The mini playfield edge should have been covered with some kind of protective cover from the factory. Unfortunately, it wasn't. Wood that is directly exposed to ball impacts will never last long! The ramp protector is also a good idea if your ramp is damaged or cracked, or the factory-installed protector is missing. You can get protectors for the lock holes, as well. There are a lot of reproduction parts available locally for Doctor Who, such as decals and parts for the mini playfield (PSPA, Mr Pinball). Prototype games were also released with a moving Dalek topper. The software to drive the Dalek is still present in the game, so you can motorise your own topper if you can get a motor and associated parts. There used to be several (expensive) kits you can buy that included everything you needed, but none are available anymore. Various people have created homebrew kits and there is enough information online to fabricate your own parts (Basement Arcade Classics, Missing Piece Technologies, Pinball Toys UK). There are various other homebrew guides, so search around. I grabbed some nice custom instruction and pricing cards from Pinball Cards. Pinball Cards have two awesome sets for Doctor Who, but I preferred the Version 2 style myself. The layout of this set of cards seems much easier to read to me than Version 1, but to each his own! Please consider donating if you download any cards from his site.  Conclusion Doctor Who was, without a doubt, the most irritating and painful machine to work on thus far. This was mainly due to having to repair the mistakes of others (such as removing posts) and tedious mini playfield troubleshooting. There was as much work in repairing the mini playfield as there was in restoring a normal, full-sized playfield! In my opinion, the mini playfield is horribly under-engineered in some ways (such as having bear wood exposed to ball impacts) and incredibly over-engineered in others (the entire mini playfield motor, cam, and bracket assemblies). But don't let that make you think that the whole process wasn't fun. It was! Just not in the same way that a simpler restoration is fun. I learned a lot about woodworking in this restoration, which is something that will come in handy when I need to rebuild the mini playfield on my second Doctor Who. I also learned a lot about the importance of properly made electrical connections. Preventative maintenance such as replacing the mini playfield motor connector is something that I will do on all Doctor Whos from now on. As I had another Doctor Who in the restoration queue, this one was on the chopping block to make some room and recoup some of the money I had spent on it. When I restore the second machine I'll have a think about whether it is a machine I consider a keeper. For now, at least, I am happy not to have to see the underside of a mini playfield again! I also captured a few videos of the machine in action after restoration. Check them out!
2 Comments
Jamie elliott
14/6/2019 07:08:25 am
Hey mate I am chasing a Darlec head on top of the back board for my doctor who pinball machine can you help me Your comment will be posted after it is approved.
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Here you will find logs of our pinball and arcade machine restorations, repairs, discussion about general pinball and arcade topics, as well as recounts of our random pinball adventures.
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Running this website is a hobby for me (just like pinball!). I like being able to show off my restoration work so everyone can learn from it and potentially fix their own machines. If you enjoy reading the site's content or it has been helpful to you, please consider donating to offset some of the website's operating costs. |
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