Reviving a Midway Space Encounters

RobotWorkshop

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Trying to revive an old Midway Space Encounters. Game wasn't working at all but is now showing some signs of life. Did some initial adjustments on the monitor and it is working. Temporarily popped in my spare 280 ZZZAP boards to confirm the screen works. It needs cleaning, recap, and adjustments but at least it is working.

Rebuilt the power board and have all three voltages present and adjusted within range so that part is good. Now it's on to the Game board itself.

I have the original boards for the game as well as an extra correct -L000 main board and spare Space Encounters daughterboard. So far neither set is running. Once I get one going that should help get the extra boards rebuilt too. At first there wasn't much working on either set of boards. Carefully cleaned all the socketed chips, replaced a few legs on three PROM's, installed all new dual leaf DIP sockets, replaced the 10uf electrolytic capacitors on the main can daughter board, and replaced the larger tantalum capacitors on the main board. Also cleaned the crystal connections.

One board is strapped for the 9314 ROM's and appears to be correct. The other main board is strapped for normal 2716 EPROMs (not the TMS version) and I burned a fresh set of 8 EPROMs for that board.

Now I need to start digging a bit deeper into the boards. Haven't made a test harness for the 8080 boards so am doing it all in the cabinet at the moment.

I've read that bad RAM is common on these boards. Not sure from the pictures if it looks like bad RAM or some of the addressing logic. I have a tester that will check the RAM chips. I'm temped to carefully pull out a set, clean the leads, test them, and socket them. Also have an HP logic comparator that should help verify of flag some of the regular logic IC's.

Have any of you run into screens like this when working on a Midway 8080 board set? Do any of the images look familiar?
 

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I pulled all the RAM on both -L000 main boards. The original main board had two bad RAM chips. The extra main board I picked up as a spare had 12 bad RAM chips. I had a few extra RAM chips but not enough for both boards. Going to clean all the leads and install new sockets on both boards. I had always read RAM on these is a known failure point but didn't expect so many bad RAM chips.

At first all the RAM failed the tests. That didn't seem right so I checked my tester and found out that the -5V supply was missing. I have the Neoloch tester and this is the first time I used the 9060 RAM blade for it. Did some diagnostic and found that the -5V was being generated ok. Ended up being a bad relay. Swapped that out from a 4116 blade (which I rarely use) and fixed that. Going to order a couple extra relays to get the 4116 blade back together and keep a spare on hand.

Once I have all known good RAM will see how the testing goes.
 
Found one more bad RAM chip. Now have a main board that is running! Was able to play a couple games on it. Still have lots of little things to do and also have to work on the 2nd boardset.

Going to re-cap the monitor and get that dialed in, verify all the sounds are working, clean the controls, swap the bulb with a Red one. Then one it is all working will do some cosmetics.

Still need to try and track down the colored gel for the screen or try and make one.
 
Took a step backwards. After leaving the game on for a while several of the sounds that I had disappeared. I swapped out the sound board with the spare I had rebuilt and have all the sounds back. Going to look at the original sound board and see what failed on that. I suspect that some of the LM3900 chips decided it was time to fail after their long slumber. Will get that board fixed while I try to find a reasonable priced set of RAM for the other main board. Really need to get that full set of 16 chips for that board. Then troubleshoot any issues it may still have.
 
Ended up pulling all of the LM3900 chips on the original sound board then installed new dual leaf DIP sockets. With new LM3900's installed all sounds are back and original sound card in place again. Having a working spare helps.
 
You are doing some great troubleshooting here, and documenting what you did and why.

Good work!
 
I forgot to mention that the 50K pot was cracked on the spare sound card and bad on the original one. I found the exact brand to replace them and popped out and moved the adjustment wheel that snapped in the new one. The leads on the new vertical control were a hair different than the original but they fit fine. All the large tantalum caps were replaced as well as the few electrolytic capacitors. Made sure to use the correct axial ones.

Just found some reasonably prices RAM so I have enough coming to try and revive the spare MPU board. Should be an interesting challenge. At least with all the RAM socketed now if any fail in the future it should be an easy fix.

Will be nice if I can find the colored GEL for the screen but the game is fun even without it.
 
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I wondered who bought that Space Encounters from Gary! :cool:

It looks like you've made some nice progress. I've restored a few of these over the years and have taken a vested interest in them due to all the bells and whistles added to what was the aging 8080 platform at the time. This was Midway's last black and white game and adding the strobe light and red bulb in addition to the color overlay really made you forget an ancient 23" monochrome tube was driving the entire thing. The game is pretty fun, too!

Some tips to help save you time:
  • This tri-volt RAM is particularly sensitive to missing -5V. There were some service bulletins issued by Midway warning technicians that significant RAM damage would be present if the power supply had a failed -5V rail. If you come across any 8080 boards and wonder why a large chunk of them are bad, this could be the reason. It sounds like you had a tester issue to resolve, but just saying this for general knowledge.
  • When you have jail bars as shown in your original post, RAM is most likely the culprit. You may already know about this (maybe not), but Midway provided a fantastic 8080 guide back when knowledge was power, as they say, and repairing boards needed to be done in a timely fashion. This took out much of the guesswork.
  • If your strobe light is burned out (usually the case), you can harvest one from an old Polaroid instant camera. Years ago, this used to be a viable option as any thrift store had dozens on the shelf. Thanks to the hipster crowd these days it might be a little more challenging. There are probably other options if you dig around online, too.
  • The original red bulb was a 200 W incandescent. You won't be able to find anything close to that today. The 60 W red party bulbs are 'okay' (kind of dim) and a super bright red LED just doesn't have the same fading effect when the light is turned off as an incandescent. I think the latter looks kind of cheesy but that's just my opinion. Most people won't care. :)
  • Don't deviate from the -L000 main boards as these are the only revision to contain the extra circuitry that drives the 'all white' screen strobing effect. Also beware of upright vs. cabaret board differences. The upright used standard composite video like all the other 8080 games before it. The cabaret had a funky, different monitor that required non-composite video. I doubt many cabaret boards are floating out there, but it has caused confusion for a couple people on here previously.
 
Sounds like you have a lot of experience with these! I hadn't seen that service Bulletin about the missing -5V but will definitely watch out for that. Rebuilding the power supply was one of the first things I did. After it was stripped down it was washed before building it back up. Actually all of the boards were washed clean to start and then the back sides got washed off again to clean off the flux residue.

Still learning all the details on these early Midway boards. I read through that guide when working on the board for my 280 ZZZAP. I had hoped on the Space Encounters it was a RAM issue and got lucky on the original board set with 3 bad RAM chips. The second main board we'll see once I get the new RAM installed. If that doesn't do it then maybe some of the surrounding logic may be toast too.

Definitely is an interesting game and more of an experience to play. I need to check the strobe unit but if it is bad I think I have a couple spares from the Polaroid camera. I had parted out a few other those since it was a cheap way to get the sonar sensors for replacements that I used on some of the early Personal robots. That was a common sensor to use. Figured the strobe may come in handy so those were just boxed up. Seems like it was a good idea to save those.

The game just had a regular incandescent bulb in place of the red one. Bought a pair of 150W equivalent RED LED bulbs off Amazon. Put one of those in there and it seems to look ok. Maybe not the same fade as original but it isn't instant on/off either. Plus less power and heat. At least it is better than the white one!

Game play is better than I thought it would be. Definitely one that MAME can't do it justice. Really needs to be played on the original cabinet. Before this one I missed out on three others over the years. It was one that I had hoped to own someday. Going to see if I can get my daughter to touch up the cabinet. May try to make up a colored GEL at some point.
 
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