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Old 28th Nov 2011, 5:32 pm   #1
musonick
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Default 1978 invaders arcade fault?

Hello, firstly, this is my first post to this section and I hope I am in the right place. Secondly, I hope this subject is appropriate to the VR forum.

I have a 'Yachiyo Electronic Co. of Japan' cocktail arcade version of Space Invaders (Taito). It is a b/w clone version using coloured gels over the monitor. The boards are copied from the Taito version but have different pinouts/connectors etc. No schematics are available.

I have a regular linear gap on the graphics (see photos). the gaps are half inch apart and appear to move with the graphic (ie they stay in the same place). At a glance they look like they are intended and do not affect game play, but it would be nice to get it sorted as this is a very early coin op classic.

It is worth mentioning that the game plays with like chess with opponents sitting opposite each other. the graphics turn to face the player. Also the lines are actually vertical on screen, the game is turned through 90 degrees. (hope the photos explain this better than I can),

I am assuming it is a board fault rather than the monitor. Any help appriciated.

Thanks, Nick.
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Old 28th Nov 2011, 5:59 pm   #2
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Default Re: 1978 invaders arcade fault?

I have no particular experience with Space Invaders, but it looks like one out of 8 bits output from some character generator ROM is missing, or there's an address decoding fault. First thing I'd try is simply removing and re-seating all the EPROMs. If that doesn't fix it, have a look at the data pins (pins 9/10/11/13/14/15/16/17 if they're 2716s) of all the EPROMs with a scope or logic probe and see if any of them are stuck.

Chris
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Old 28th Nov 2011, 9:23 pm   #3
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Default Re: 1978 invaders arcade fault?

Hi Chris, Thanks. I reseated all the eproms but no luck. As far as checking the data pins, I honestly wouldn't know how to go about it. Also, all identifying marks have been removed from every single chip but I am fairly certain most correspond to the Taito version. Seems they didn't want their clone... cloned! I shall dig out my scope and Google how to test an eprom.

Nick.
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Old 28th Nov 2011, 9:45 pm   #4
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Default Re: 1978 invaders arcade fault?

Just a note. When the game switches to player 2, all is fine.
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Old 29th Nov 2011, 1:12 am   #5
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Default Re: 1978 invaders arcade fault?

Quote:
Originally Posted by musonick View Post
Just a note. When the game switches to player 2, all is fine.
Ooh, that's a subtle one. Probably something deep inside the video generation logic, then. I couldn't hypothesise further without a schematic...
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Old 29th Nov 2011, 2:23 am   #6
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Default Re: 1978 invaders arcade fault?

Quote:
Originally Posted by musonick View Post
Seems they didn't want their clone... cloned!
Nick.
..... Or get "done" for nicking someone else's IP .
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Old 29th Nov 2011, 11:50 am   #7
musonick
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Default Re: 1978 invaders arcade fault?

Well there is a repair to the board, a jumper wire between two unknown 16 pin chips. I will 'un-repair' this and see what happens, try to identify the mystery chips and replace. Probably unrelated but a start.

Thanks.
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Old 29th Nov 2011, 12:10 pm   #8
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Default Re: 1978 invaders arcade fault?

Hi,
make sure you make a clear drawing of any mods that you disconnect, in case you need to put it back. with regard to the eproms the data lines should normally have signals on them when the game is working. if one of the data lines is stuck either at 0 or + 5 volts then this could be a fault.
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Old 29th Nov 2011, 2:05 pm   #9
musonick
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Default Re: 1978 invaders arcade fault?

Ok, cutting the jumper scrambled the graphic on screen so one of the chips is bad. The jump is between the bottom left and top right in the close up photo.

I have put up a photo of the complete board should anyone be able to identify what the chips are.

thanks, nick.
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Old 29th Nov 2011, 5:44 pm   #10
Malcolm G6ANZ
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Default Re: 1978 invaders arcade fault?

I wouldn't jump to the conclusion that theres a bad IC. I've seen lots of boards that have jumper wires added apparaently as an afterthought. If removing it stops the game working totally then its probably original and needed.

Malcolm
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Old 29th Nov 2011, 6:04 pm   #11
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Default Re: 1978 invaders arcade fault?

Point taken Malcolm. This is tricky as there is so little info, being a cloned machine.
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Old 29th Nov 2011, 8:23 pm   #12
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Default Re: 1978 invaders arcade fault?

Hi, having worked in the leisure trade for a number of years. I have seen many boards with links added, ether added from new (someone got the PCB wrong at design stage) or the Game has been "up-dated" with new EPROMs and some adjustments were then made to the logic functions.
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Old 29th Nov 2011, 11:24 pm   #13
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Default Re: 1978 invaders arcade fault?

Hi Musonik,

Many years ago I worked with machines like this, but my memory is failing now !.

Firstly, the 'point to point' wire is highly likely to be 'original'. As Seymour said, there were many brand new boards with patch wires and track cuts to correct design mistakes.

The missing row is likely to be a stuck data line somewhere, but I wouldn't jump to the conclusion that it's the character generation ROMs.

This because the characters are OK on player 2, so it's more likely to be something after the char ROMs.

This also gives you a huge clue as to where to start looking - the fault is related to the current player !.

There were two methods I remember of switching the the picture 'end to end', so that the players got the right view.

One method used a relay to swap the scan coil, thus inverting the picture.
The other method was all done in logic, actually generating an inverted picture.

If yours is the 'scan coil switch' method, then tracing the circuit back from the relay driver should get you somewhere.

You will obviously be looking for a short, but also chips which which are involved in more than one part of the circuit. By this I mean something like a quad NAND, where one gate is in the player logic and another in the video logic.

A circuit diagram would help enormously, but even without it it should be possible to have an educated guess as to what the chip is, based on the Taito circuit and others of the same era.

( Have you got a Logic Analyser ?. These are invaluable when trying to determine unknown ICs. )

You've got a 99.9 per cent working board, with what looks like a 1-bit error.

It will be a challenge to fix this fault, but well worth it in the end.

Good Luck,

Buzby
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Old 1st Dec 2011, 10:36 am   #14
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Default Re: 1978 invaders arcade fault?

Have a look at MikesArcade.com here: http://www.mikesarcade.com/arcade/manuals.html where you can download the original Space Invaders schematic.

If this Yachiyo Electronic is a good copy it will probably look a lot like the original Space Invaders in the design.

This game is actually called "Space Stranger" and was followed by a colour version called "Space Stranger 2" if the information I have read is correct. You can find some Youtube movies and also some information here: http://maws.mameworld.info/maws/romset/sstrangr .
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Old 1st Dec 2011, 9:36 pm   #15
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Default Re: 1978 invaders arcade fault?

Sometimes IC are marked underneath! It might be worth checking this if you can remove one carefully.



Rich.
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Old 1st Dec 2011, 10:56 pm   #16
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Default Re: 1978 invaders arcade fault?

If it is a really good copy it should be possible to see which blank IC corresponds to an original IC by checking what analogue components like resistors and capacitors are connected to it. Usually the analogue design is kept with the correct components and by eliminating just a few IC's by how they are connected to the analogue componets it should be easy to check the rest.

And don't forget to ask questions at Mameworld or Mikesarcade, someone might have done this work earlier.
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Old 2nd Dec 2011, 11:13 pm   #17
musonick
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Default Re: 1978 invaders arcade fault?

hi, yes thanks. i managed to fix a couple of missing sounds via the midway schematic. it uses the same op amps. that was the easy bit. the layout & pin out, as you can see it the photo, are quite different. i shall get the scope out over the weekend and see what i can find.

thanks, nick
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Old 3rd Dec 2011, 12:36 am   #18
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Default Re: 1978 invaders arcade fault?

At least yours has replaceable technology, I encountered this at work the other day, the small board is the entire computer with its 156 games including space invaders built-in to the 'snot' on board.

The Video side of things appears to be a normal CRT tv with HD (monitor) tube and the Tuner removed (tuning circuits, SAW filters etc still in place) and forced into AV mode permanently.
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Old 3rd Dec 2011, 12:45 am   #19
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Default Re: 1978 invaders arcade fault?

Quote:
Originally Posted by davegsm82 View Post
At least yours has replaceable technology, I encountered this at work the other day, the small board is the entire computer with its 156 games including space invaders built-in to the 'snot' on board.
Ooh, that's really nasty. I especially like the bit of tape holding the power connector.

The old arcade boards are fun to fix - I've got a 'Bomb Jack' on the workbench at the moment. With a schematic, tracing signals around with a scope is reasonably straightforward. I've frequently found that there's something stuck at 1, 0 or (surprisingly often) logic half!

The Space Invaders clone probably has many similarities, even in chip locations, with the original, so it may not matter too much that the legends have been obliterated. Many bootleg boards are almost a straight copy. However, this one is a radically different shape from the original...
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Old 14th Jul 2012, 8:36 pm   #20
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Default Re: 1978 invaders arcade fault?

Hi there, this link might help, they have the schematic - link

If not, have a look here this guy has the space stranger 2 manual, but it's the same board.

Hope you can contact them, all the best..
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