A&F Pinball Restorations
  • Home
  • About
    • About us
    • Our pinball cats
  • What We Do
    • Repairs
    • Hire
    • Machines for sale
    • Parts for sale
    • Wanted
  • Resources
    • Restoration blog
    • Restoration process
    • Links
  • Contact

Doctor Who mini playfield edge repair

17/12/2016

0 Comments

 
Having repaired a couple of Doctor Who (Bally, 1992) machines, I've found that the Time Expander mini playfield always needs to be rebuilt. There are two main parts to this:
  1. Rebuilding the mini playfield (and main playfield, if necessary) wood edge;
  2. Rebuilding the mini playfield gearbox and cleaning the entire assembly.

This is a small write-up of how I approach these repairs and what the end result looks like.
Rebuilding the mini playfield wood edge

As the mini playfield has an exposed wood edge that balls can hit, it eventually gets worn down, forming divots in the playfield wood and, eventually, chipping up the playfield artwork. The worse the damage is, the more will need to be repaired. In this post I'll just cover the procedure I use to carry out wood repairs to the playfield. Check out my first and second Doctor Who restoration posts for examples of playfield artwork touch-ups. If your mini playfield has never been serviced or rebuilt, it will probably look a lot like this...

Picture
Mini playfield edge damage: top view
Picture
Mini playfield edge damage: side view

Yikes. Plenty of wood damage which has started to impact on the plastic insert, as well. The first step is to clean and then sand down the playfield edges slightly so that any loose wood fibres are removed. Use a coarse grit sandpaper as you want a rough surface for the wood filler to adhere too. If it's too smooth, the filler won't be able to stick.

Next, we can apply some filler. Vid's restoration guide recommends Woodwise Epoxy Wood, which is a two-part filler. It's not available in Australia, so I like to use Selley's Knead It as it is basically the same type of product. Any similar wood filler would work, but use a two-part filler instead of a premixed slurry, as the latter generally won't be as strong. Bog the filler material in and pack it tightly. Don't worry about being too neat, as you can sand it down in the next step. Apply some masking tape or other protective material over the undamaged parts of the playfield you don't want to sand. Then, sand everything down so it is flush with the original playfield surface. Use progressively finer grits of sandpaper until the finish is smooth to the touch.

Picture
Applying wood filler and packing it in tight.
Picture
Sanding the filler material flush with the playfield surface.

Then, remove the tape and clean up any areas where the filler material shouldn't be. At this point, the playfield is ready for reinforcement. You can leave these areas unprotected if you wish, but eventually they'll chip and crack like the original wood. A product like Cliffy protectors or Mantis protectors is the best way to protect commonly damaged playfield areas. Cliffy offers a set of protectors for Doctor Who. You can use this procedure on any game that requires wood repair before applying a Cliffy protector. It's always a good idea to repair this kind of damage first, so the Cliffy protector doesn't warp or bend into the damaged areas when struck by the ball.

Picture
Mini playfield edge after repair: top view
Picture
Mini playfield edge after repair: side view

And that's about it! Pretty simple, really. The next stage would be artwork touch-ups, as necessary. Most protectors are designed to cover repaired areas, so sometimes art touch-ups aren't even required, depending on the damage.

Picture
End result after wood repair, protector installation, and artwork touch-ups.

Rebuilding the mini playfield gearbox and cleaning the entire assembly

This task is a painful one as there's a lot to clean and a lot to disassemble/assemble.  For this, refer to Faz's Doctor Who mini playfield guide. He gives an excellent rundown on how to take things apart, test them, and put them back together again. Download a copy below:
The Doctor Who Mini Playfield v1.2.pdf
File Size: 2036 kb
File Type: pdf
Download File


The best advice I can give is simply to take plenty of pictures when disassembling the unit so there's no confusion when putting everything back together. The most important thing to do is to clean the old grease off the cam assembly (part no. A-15035) and the motor gearbox (part no. 14-7970). The old grease is typically very dirty and, in some cases, completely dry.

Picture
Cam assembly after removal from the mounting bracket. Greasy!
Picture
Motor gearbox after disassembly. Also greasy!

Cleaning the grease off is as simple as using your favourite degreaser and some elbow grease. Isopropyl alcohol also works well. Any hydrocarbon solvent will do the trick. You'll probably need to use a toothpick or other fine tool to clear the dry grease out of gear teeth. Once it's all clean, make sure everything is completely dry before reassembly. Use your favourite bearing lubricant to grease the gearbox gears and the cam assembly. The president of Multi Products, the company that makes pinball machine gearboxes and motors, recommends Magnalube for this purpose. However, Magnalube isn't readily available here, so I use Nulon Extreme Performance Grease, which is another Teflon-based lube. However, if you wish, you can order Magnalube from Seal Innovations, based in New Zealand. There are a lot of resources online that discuss other aspects of cleaning and regreasing pinball motors and gearboxes - they're all well worth a read. Here are a few (while they talk about gearboxes in specific machines, the concepts are universal):
  • Martin's Monster Bash Dracula gearbox rebuild;
  • Vintage Technology: Addam's Family Thing motor gear repair and rebuild;
  • Pinball Supernova: Monster Bash Dracula motor rebuild;
  • Firebird Pinball: Johnny Mnemonic gearbox rebuild.

The next tricky part about reassembly is aligning the cam assembly on its mounting bracket. The alignment needs to be just right to ensure that the playfield doesn't bind or shimmy when it moves up and down. Faz has some good instructions for aligning the assembly in his guide. Test the assembly with a 9-volt battery or external power supply to make sure it works before it goes back into the machine. If it moves cleanly, then it's ready for reinstallation and play testing!

Picture
One Doctor Who mini playfield assembly after a full rebuild and clean.
0 Comments

Your comment will be posted after it is approved.


Leave a Reply.

    About

    Here you will find logs of our pinball machine restorations, repairs, discussion about general pinball topics, and recounts of our random pinball adventures.

    Check back regularly for updates!

    Blog updates

    RSS Feed

    Archives

    December 2022
    July 2022
    March 2022
    December 2021
    November 2021
    October 2021
    May 2021
    November 2020
    July 2020
    May 2020
    January 2020
    December 2019
    November 2019
    September 2019
    July 2019
    March 2019
    October 2018
    September 2018
    June 2018
    April 2018
    December 2017
    October 2017
    August 2017
    January 2017
    December 2016
    July 2016
    April 2016
    March 2016
    November 2015
    June 2015
    March 2015
    December 2014
    November 2014
    October 2014

    Categories

    All
    1978
    1979
    1989
    1991
    1992
    1993
    1994
    1995
    1996
    ACT Pinball Championships
    Bally
    Circuit Board Repair
    Collector Con
    Data East
    Demolition Man
    Doctor Who
    Elvira And The Party Monsters
    Events
    Fish Tales
    Frankenstein
    General
    Getaway
    Gottlieb
    Guns N Roses
    Johnny Mnemonic
    Judge Dredd
    Jurassic Park
    Last Action Hero
    Nerd Con
    Pinfest
    Playboy
    Six Million Dollar Man
    Star Trek
    Stern
    Tales Of The Arabian Nights
    Tee'd Off
    Teenage Mutant Ninja Turtles
    Trident
    Williams
    World Cup Soccer

    Donate

    Picture
    Running this website is a hobby for me, just like pinball. I like being able to show my restoration work to everyone so that others can learn from it and learn to fix their own machines. If you enjoy reading the content, please consider donating to offset some of the website's operating costs.

  • Home
  • About
    • About us
    • Our pinball cats
  • What We Do
    • Repairs
    • Hire
    • Machines for sale
    • Parts for sale
    • Wanted
  • Resources
    • Restoration blog
    • Restoration process
    • Links
  • Contact