Wizard of Wor repair log

 

This game uses 6 PCBs – an unusual design.

I have been working on a Wizard of Wor machine that wouldn’t start. The only thing I got was a vaguely green screen and a buzzing speaker. I began by removing the socketed chips one at a time and cleaning them with a high quality plastic eraser and a Dremel wire brush when the tarnish was too heavy. After this I sprayed Deoxit into all of the sockets and reseated the chips several times each.

I checked the power supply and found that there was no voltage on the +12v line. If all voltages are not present, the supply will not send the 5v “power good” signal and the game will not boot. My first thought was to replace all the capacitors on the power supply since they are at least 37 years old at this point. However, I still didn’t get any change. I also tried changing out the variable regulator that controls the 12v to no avail.

It was suggested to me that the small tantalum capacitors on each of the 6 game PCBs are known to short out. While I was testing another point on the power supply, one of these capacitors on one of the game’s two RAM boards exploded, so I went ahead and replaced them all with these. After that the game booted!

The shorted capacitor exploded so hard that it actually broke in half.

However, the display was completely scrambled. Another tip I got was to adjust the horizontal frequency control deep in the recesses of the monitor chassis. Turning it all the way up, I was finally able to get a steady picture, but it was a bit unevenly projected, most likely due to old capacitors. There were also two sets of vertical yellow lines at even intervals across the screen. The cause of this turned out to be some bad RAM chips.

To test the RAM chips, I burned Mark Spaeth’s excellent GORF test ROM since Wizard of Wor uses the same hardware. I had to create an adapter to burn it onto a 2532 EPROM because my programmer isn’t compatible with them out of the box.

I also had to bend a pin out and wire a jumper in place so it would not be damaged by the ROM board (which still uses the original mask ROMs.) I found this information in the readme file for an earlier Wizard of Wor test program, WOWMD.

After finally getting the chip on the board, I was able to test the RAM.

I ended up having two bad RAM chips on the board with the capacitor that exploded.

I replaced the original 4027 chips with 2104 RAM, which is a drop-in replacement.

 Now the game is up and running. I need to replace the capacitors on the monitor to correct some display geometry issues, and that’s it. I’m also planning to put heatsinks on the game’s special Astrocade chips since those are known to sizzle, and without them we’d have a dead game on our hands. Since the original heatsinks that Midway used are pretty hard to come by now, I found some alternatives I think will work nicely for about 50 cents each.

21 thoughts on “Wizard of Wor repair log”

  1. This is a really great ‘blog. I’m a HUGE fan of Wizard of Wor and finding technical info, deep technical info, about it just made my day. Tell me, how much RAM did it have? Did the system have a discrete CPU or was it just logic? I’m guessing it was a z80? Or was it a 6809? Is the votrax (if that’s the correct hardware) board in the main cage pictured or is it a separate subsystem?

    Anyway thanks for this cool ‘blog post regardless!

    1. The Votrax chip is indeed on one of the boards in the cage. All of the game circuitry is in there. It’s a pretty unique design, and the only other game that runs on similar hardware is GORF.
      It has 16 RAM chips on each RAM card, and each “4096 word x 1 bit” RAM chip equals, I think on an 8-bit CPU, 512 bytes, so I think the game runs on 16k of RAM. I’m not an expert by any means so my calculations could be off.
      You are correct, the CPU is a Z80. Glad you enjoyed reading my post!

  2. Great work !! Thank you so much ! Also thank you for the component links !
    Where can I find this test rom exactly ?

    Best regards
    Marco

      1. Excellent info, I’m attempting repairs on my WoW which just went down. Once I have the test rom programmed, where do I install it, at which location and on which board?

        Regards,
        Ivan

        1. The file included in the zip should have this info, but just in case, the ROM should go in position X1 on the ROM board.

      2. That domain seems to be forgotten. Do you by chance have the files so I may create a chip? I’m in the midst of a rebuild and would like to use the test program once I finally get video. Thanks.
        Tom

  3. hey there
    are all the titanium caps the same on all the boards? I’m fairly sure its my CPU board thats giving me issues as I get no 12v if its plugged in but I do when I take it out of the slot.
    LMK ~sm

    1. Hi,
      Yep, that sounds like it could be caused by a shorted tantalum cap. That link to the replacements I provided should work for all of them. I would just replace them all so you don’t have to worry about another one shorting out down the line.

  4. Standard electrolytic caps – 22uf @ 50v axial – will work just fine and are a lot cheaper than using tantalums, plus they won’t explode.

  5. Hello,
    I am searching for a PROM set for WoWor. I am restoring a machine my self. And I broke the pin off of PROM number 1.
    Can you please help me find a copy to finish my repair? Thanks in advance.

    1. Hi!
      What I would do is contact someone like Hobby Roms and see if they can burn you a replacement for your damaged ROM. There’s only one ROM set for Wizard of Wor so you shouldn’t have any compatibility issues. If they can’t do it for some reason, you can contact me here again or you might check around on the KLOV forums. Hope this helps you get your machine up and running!

  6. Hoping to find some help here, I just acquired a wowor cabinet from an uncle that just passed. I have it turning on but that’s it. The monitor comes on, but it’s just white/grey. No sound no game booting. Found a hot spot on the U15. (I know, I know impossible to find.) Hoping for some leads maybe for some cpu cards or maybe the individual customs. Any help is appreciated. Also any other ideas of troubleshooting? I haven’t done any actually meter checking yet because I just got it yesterday.

    1. I would definitely check the voltages first, because that sounds very similar to how mine was when I got it. You should be able to test at the connector on the power supply board. If you find any that aren’t nominal, you’ll want to get those fixed first before assuming there’s anything else wrong. My 12v line was dead due to the shorted tantalum capacitor in my post, and that resulted in a dead game until I replaced those capacitors.
      As for leads on parts, I would say to check the KLOV forums first, but only once you’ve determined that it isn’t something you can fix with off-the-shelf parts.
      As for the custom chips, I don’t know if anyone is making reproductions yet but it has to be possible since the game is implemented on MiSTer, so there’s always hope. I hope this helps!

      1. Awesome, I’ll definitely try that first, was stoked just that the screen turned on as it’s sat for about 20 years unused. I feel sure we will get it going!

  7. Well with some further investigation, looks like I overlooked a blown fuse that goes from transformer over to power supply. Unfortunately in the midst of getting ready to go hunt down a fuse, I was going to slide the back panel back on to cover everything up so my kid couldn’t mess with it while I was gone, and the panel was coming apart and ended up crumbling in the middle and fell on the neck tube broke it and de gassed the tube…. When I tell you I am heartbroken I am not lying. As far as I can tell this machine was completely original……. So any leads on a tube would be greatly appreciated! I may can unhook the tube and still keep troubleshooting the rest, maybe if the fuse fixes it I can get sound? Assuming there are no other issues.

    1. Wow, I’m sorry to hear that. My answer is the same as before – check on forums. If you can tell the make and model of tube, there are still some places that you can get replacements or equivalents, but I’m not sure what they would be off hand. If you can’t get a NOS replacement, someone on KLOV or Arcade Controls can probably help you track one down.
      You should still be able to troubleshoot the game without a monitor. If it boots, it should play some sinister chords right away.

  8. I believe I have traced my problem down to the audio amp. If left hooked up it keeps blowing the 1.5 250 v fuse. With it unhooked it doesn’t blow. It seems to look ok, not sure the best way to test it. Any ideas?

    1. Off hand, unfortunately no. At this point I recommend signing up for the KLOV forum and asking there. There are people there that have a lot more expertise diagnosing stuff than I do.

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