Space Invaders showing nothing but garbage and other oddities

Pulseman

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Space Invaders showing nothing but garbage and other oddities

I'll try to make this quick,

Backstory: Just picked me up a SI that had a blown power supply. Seller included a new power supply to replace it. I get it all home, assemble it and the monitor wouldn't power up. Switch to the old supply and still nothing. I couldn't get it to coin up at all since the coin switch's wire was cut, but fiddling with it made the game start playing the UFO sound effect on loop. Turns out it was a blown fuse on the monitor was why I got no picture (derp). This brings me to my current shenanigans:

All the game throws up is garbage, there was one moment where the garbage was animating the exact same way the attract screen does, but now its just a blocky mess... How do I begin to debug this?

IMAG0179.jpg

Side note: what game does this color overlay come from? Cause it doesn't look like its from SI
 
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if it's the Midway version I'd buy the braze multi kit. Installing the kit alone might fix the problem and if not I'm pretty sure it ads a diagnostic feature that will likely tell you what is bad.
 
I'm already planning on getting the braze kit lol, I just don't have the cash as of yet, just blew my reserves on the cab :p

I tried cleaning off the contacts where the board plugs into the harness and where the second board plugs into the first. Still nothing
 
Sounds like you and I might be able to help each other. I have an SI that I am trying to get working. Personally can't get it to coin up.

As for your picture problem, it might be the reset circuit on the power supply. I read that was a common issue, and the screen garbage looks similar to yours. I had a similar problem with mine, but reseating the EPROMs and cleaning all the board connections fixed it.

Did you bridge the coin lever connections? When I do that on mine, it registers as a credit on the counter, but not in the game. The two wires for that are brown with a white stripe, and brown with a black stripe.

Hope some of that info helps you out.
 
Thats a reset issue...check your power supply reset circuit (check Elektron forge site for instructions).

Also check the weighted switch on the coin door to make sure its not connecting.
 
So I followed the instructions over at elecktron forge, and unless my meter is borked that reset line only holds at .5V for a second before getting surged to hell and back.

and I think I pissed the power supply off, I know I didn't bridge a connection, but when I tested the line the sfx for the UFO started playing again, with a large hum in the background. Testing the rail without the PCB attached results in the same spikes. Any advice?
 
Force a reset (fake what the circuit does....i just don't remember what to short..instructions are out there though) and see if the game attempts to boot.
 
Also, confirm the voltages via the test points listed on the elektron forge docs. Don't want to kill any ram, that is where the real fun starts... Probably won't hurt either to just order the rebuild kit from Bob Roberts (takes maybe 15 mins to install..and you will need jumper wire for 2 of the caps) and reflow the connector on the power board (careful not to create a bridge)
 
Yea it didn't dawn on me to check the other lines lol, and I'd get the rebuild kit if I wasn't so damn impatient.

What would happen if I were to hook the supply up with that reset line not attached? Would that break things worse?
 
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Whelp we can rule out a reset line issue, replaced a cap on the one trace and I get a solid .24V, Upside is that it seems like its registering coins now, even if nothing goes on screen, before the coin counter wouldnt even increment. I checked all other voltages and they all seem fine, Still showing garbage. I guess there's a bad chip somewhere

and while testing the board it would one and a while start screaming the UFO sound and nothing would come on screen
 
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Its not really recognizing the credit, as long as the db is getting proper voltage the credit switch will trigger the coin counter even if everything else is doa.

If the screen pattern didnt change at all, its still a reset issue but now on the daughterboard. The random sounds can me a symptom or just you touching various traces can trigger them.

You can try grounding the reset pin to see if it boots...its the orange wire on the top left plug on the daughterboard(verify that in them schem). If that works...ps still needs work, and dont leave it that way.
 
Ah, alright so all I have to do is trace the reset rail up to the daugherboard and see whats up there right? And don't worry, I fully intend to repair the power supply I just need to see if the board itself is working, especially since I believe I cooked one of the ROMs

What happened was that I decided to pull out all the game ROMs to do the whole "see bars to check RAM" crap, and I noticed that one of the game ROMs looked like it was put in upside down, so when I put it back in after testing I flipped it to what I thought was the right way around. All i got was a white screen on boot

I learned 2 things:

1) I need to learn to keep schematics on hand at all times
2)the Braze multigame kit skips those ROMs so at least I'm not entirely hosed
 
Lol thats why working on the reset circuit is #1 on my list, but I won't be able to work on it until tomorrow
 
Mine did the same thing (only B&W version) and it was a short in one of the external connecters. Doubt it's that easy but I did everything you're doing and missed it until the end so I figured I'd mention it :D Good luck!
 
Quick update: So Instead of grounding out the reset line like planned, I attached it to the test point marked on the instructions from elektronforge. I get the UFO and some kind of an alarm blaring in the background while the screen flashes horizontal bars on the left half and a solid white screen on the right and it flips back and forth. Safe to assume that the reset line now works and that the issue was that the connector is borked since if I leave the reset line not attached to anything the same garbage comes back

The flashing screen shenanigans is probably because there was a ROM flipped right?

I'll post screenshots later if necessary
 
What I'd do at this point is what's described in the "Standardized Test Procedure" document, specifically removing the ROMs and checking for the "good vertical lines" (vertical lines with the monitor in horizontal orientation, that is.)

After that, I'd make sure it's strapped for regular 2716 EPROMs (vice TMS2716) and put in a 2716 programmed with the SI test ROM. Once everything works fine with the test ROM, then I'd put in the 4 game ROMs (freshly programmed regular 2716s again). [If you have a progammer that can do TMS2716 EPROMs, you can skip the re-strapping and just use TMS2716s, of course...]

http://www.outerworldarcade.com/arcade/space_invaders/space_invaders_test_rom.html

http://www.pinrepair.com/video/seawolf.htm

http://arcarc.xmission.com/PDF_Arca..._for_Processor_Boards_(M1700-1_July_1976).pdf
 
Well the braze multikit came in and it lives!!!! Minus 2 last problems:

1) I'm missing the sound when the base shoots and one other one I don't remember
2) the screen seems like the contrast is turned up all the way on any screen other than the ram and watchdog tests. I.E blacks look black during the ram test but look grey during gameplay

any ideas?
 
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