Medieval Madness: Pinball Repair Log

Original post: September 14, 2009
Updates: ongoing

My wife and I are now the proud owner of one of the grail games of pinball collectors: Medieval Madness. We bought it from a game room store on September 3rd, and it ended up having some issues when we got it home. I have been gaining a lot of confidence repairing this machine as all of the issues have been pinpointed within a couple of hours. So, I am enjoying my time repairing this machine. ~~On the plus side, the machines warranty includes all the parts I need for 90 days.~~

ISSUES

~~Left Flipper Malfunctions:~~
- ~~Flipper stays up for about a second after release.~~
- ~~In Switch Edge test mode there is a hum/buzz that occurs as the lights on the switch matrix display are finally turning off. (This sound emanates from playfield, not the speakers.)~~
- Lane Change: At one point I saw the "R" and "E" alternate back and forth after the left flipper button is released. (I assume all four of the letters to spell "FIRE" do this, but I haven't watched closely enough to verify.)
~~End of Ball / Multiball.~~
~~Flash Lamp Shorts.~~
~~Right Troll never registers hits.~~
Fried Switch Matrix!
Switch Flakiness:
- Right Skill Shot Lane.
- Castle Gate.
Catapult Kicker Power: starts strong and fades throughout a game.

DETAILS

Left Flipper

[9/5] The flippers on the WPC machines use optical switches instead of leaf switches. There is a "F" shaped piece of plastic which normally blocks the opto switch light. This plastic was leaning slightly away from the opto board, which was apparently causing these crazy things to happen. I also discovered the left opto was missing a piece of spring steel. Transferring the steel piece from the right flipper resolved the problem.
[9/14] Installed new piece of spring steel on the left flipper button assembly, and returned the other piece back to the right side to resolve the problems.

End of Ball / Multiball Issues

[9/5] A new acquaintance of mine told me the balls are getting caught high in the trough so the opto switches are not registering the balls presence. The solution is to replace the old dented ball trough. Until the trough arrives, we just have to give the game a jiggle to free the balls.
[9/14] Installed a brand new replacement trough engineered by Mantis Amusements. This trough adds a steeper incline, and uses inexpensive replaceable rods. And, the next time our trough has problems, flipping the rods over gives the trough new life! :-)

Flash Lamps

[9/5] Playing Pat Choy's MM made me realize our the flash lamps were not working.
[9/9] Discovered a blown fuse.
[9/10] Luckily every flash lamp had quick disconnects, so troubleshooting involved unplugging every flash lamp under the playfield (I now realize there are 4 flash lamps behind the translite as well). Then installed a new fuse, and began plugging one lamp in at a time until the fuse blew. The problem was a #89 flash bulb which lights up the green moat plastic. The base had broken loose and was causing a sort. Repositioning the base resolved the short (at least temporarily).
[9/12] Discovered the lamps lighting up the green moat trough are NOT supposed to be lit constantly! Uh oh! I disconnected the moat lamps (via the quick disconnect) to avoid the lamps melting the moat plastic ~~any more than they may have already done~~.
[9/13] After reading Clay's Williams WPC/WPC95 repair guide (at marvin3m.com / pinrepair.com), I believe the transistor(s) that turn those lamps on have developed a short.
[9/13] Both the TIP102 and its predriver transistor have been requested from the seller. Hopefully replacing these transistors will resolve the problem, and we won't end up having to replace anything further up the line (like the chip that tells those transistors when to activate the lamps).
[1/23/2010] Replacing Q29 & Q17 solved the stuck flash lamp problem! :-)

Right Troll never registers hits

[1/24/2010] Removed the right troll assembly to gain access to the troll head and switch. On the back of the troll head there are two screws which attach the plastic head to the switch blade. The bottom screw had almost completely fallen out. This loose screw stopped the head from moving far enough back to trigger the switch. A "switch edge test" showed the switch triggers consistently now! :-)

Fried Switch Matrix!

[1/25/2010] While attempting to clean a flaky switch, I had the playfield up and power on to the "Switch Edge Test". Although I had to keep the coin door closed due to the presence of my almost 2 year old son. Of course that meant the high voltage coils were all energized when I bumped the diode on the switch into a lug on a coil! :-(
[1/26/2010] Pat suggested I fried the ULN2803 chip (U20) which controls the switch matrix.
[1/26/2010] After reading the section titled "Check Fuse F114/F115" (or F106/F101) Message" on pinrepair.com's WPC repair guide, I found there are 3 parts that may need to be replaced. The guide says that when the U20 "dies hard" ~~U14~~ U23 (74HC237) should be replaced as well.
[2/6/2010] I replaced the LM7812 voltage regulator (Q2) on the power board. No change. So I ordered a new round of parts. Boy did I do a number on this. :-/
[2/10/2010] Replaced Power Board diodes D11 - D14 (aka BR1), and D1, D2 with no luck.
[2/10/2010] Replaced Power Board ICs 74LS374 (U10) and ULN2803 (U11) with no luck.

Switch Flakiness

Right Skill Shot Lane:
- [1/24/2010] Attempted to reposition the switch so the wireform would sit more centered in the lane. After a couple of games it seems to trigger more consistently now. I will have to keep an eye on it.
- [2/6/2010] Replaced the Right Skill Shot Lane switch.
Castle Gate:

Tags: medieval madness, pinball, repair, repair log