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Galaxians and Xevios


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Original Midway Galaxians cheers Geoff.

 

Bad 74ls138@8m

74ls194@2k Now I get a screen full of G's flashing

2114 ram@3F now instead of getting a screen full of G's i get flashing BAD RAM A. The R in Ram is messed up.

Bad 74ls74@2d and 3d. Starfield is now back :)

Found a lot of bad sockets on this board so ive gone through and replaced them all. just found a socketed 74ls393 many of the pins not making contact.

Bad 74ls175@6R output pin 2 stuck low.

Bad 74ls20 @3P pin 4 a input was low pulling down a output of a 74ls377 pin 19

Bad 74ls10@5D output was pulling the circuit low effecting the 74ls02@3P pin 6 and the 74ls377 @ 6P pin 1

Bad 74ls10@ 4P. Output pin 6 dead.

Background is now black as it should be and colour look good. The starfield is working normally in the background however there is nothing but garbage on the screen.

Turns out the wiring on my single rom hack was a tad dodgy, now the game goes through the first part of the test screen with all the letters and number scrolling sideways then resets as it goes to the nest part of the test.

Found a bad 74ls367@8D bad output pulling a address line down, didnt fix the resetting problem but.

After many hours of going over everything I finally found a dead input on pin 12 of a 74ls367 @ 8D. This lead me to a 74ls259 @ 9N outputs were dead as a door nail. Replacing the chip booted up the board. Seems to look great but aliens are stuck up the top and in the intro screen the are split half,inverted and stuck at top, also in the demo when the aliens dive they split apart then join back together.

Bad 74ls163 @ 5T was the cause of the diving aliens being stuck at the top but they are still spit in two and inverted.

Bad socket on the 74ls245@5J one of the characters was not showing up complete.

Found the split character problem was a 74ls157 @ 6J. I found a 74ls86 with a dead input pin 10 which leads to the 157 pin 13. there was a broken trace to pin 13 I fixed it but line still dead. replaced the 157 and characters are fine, pin 13 of the 157 is a input also so I need to do some more digging.The trace to this pin was cut I couldnt even see it until I ran some solder over it to repair it. In this case I used a socket when replacing the chip because the solder holes didnt look real heathy, I've actually found a few like this on this poor old board.

I can see on MAME the aliens at the title screen are upside down but in game they are perfect. this line must flip them for the title screen.

Ok pin 13 on the 157 and pin 10 on the 86 trace back to a 74ls273 @ 4L pin 19. pin 19 (output) was pulsing but somewhere the line is broken. I decided to cut the chip off to see whats underneath, Its also fair to note this chip and the 157 had been replaced by some one else in the past.

I cut the chip off desolded all the pins and with my trusty old desoldering pump cleaned the holes up. The problem wasnt the hole itself but at the end of the trace. I cleaned it up ran some solder over it and found another small cut WTF? Popped a new socket in replaced the chip fixed the trace fired her up now shes perfect!!! I have no idea why the lines were cut, it certainly wasnt due to the age of the board, shes in pretty damn good nick for something made 27 years ago!

Now I have the graphics worked out its time to finnish my harness and get the control and sound hooked up.

 

Sound:

The LM777 amp was getting super hot so bad you would burn your fingers on it until finally it died(didnt take long.

I had no replacement chips for this so I decided to make my own amp out of common parts IE: a Fairchild MB3730. Playing around for ages I found pin 2 is the output, pin 6 is the input and pin 16 is +12v. I'll go into details of the home made "bodgy amp" after.

OK started her up with LOTs of background static and noise.

Sounds that can be herd.

Coin insert

Alien explosion.

Seem to be missing heaps, I instantly suspected a 74ls259 @ 9L which like all these damn EL SALVADOR chips were corroded to buggery.

This chip(from the troble shooting guide) effects tone generation, explosion and wrong tones in other sounds.

Replaced the chip and what do you know the static background noise and hums were gone. Started the game up and I had the in game background noise, explosion when your ship dies and the alien diving noise back, still seems im missing the sound when you shoot :|

Turned out to be a simple problem. Legs broken on a 0.1k100T green cap. The trouble shooting guide helped heaps with this problem.

I also replaced the Lm234 just for the hell of it, the legs were badly corroded.

Board is now 100% working and fixed just need to tidy up my home made amp into something that looks presentable :D.

 

Home Made amp for Galaxians.

 

What you need.

 

Fairchild MB3730

Wire

220uf 16V or higher volt cap

22uf 16v or higher volt cap

4.7uf 16v cap

a couple of 154K green caps

 

First cut off the uneeded resistors and caps from the old amp @ C50, R95, R94, C48, R93, C47, R92, C51, C49, C46.

Solder the 4.7uf cap at position C46 with positive facing the volume pot.

 

Going from left to right on the amp pins 1 through to 7, connect pin 7 to pin 16 where the old lm377 was +12 V

Connect pin 6(MB3730) to pin 2(lm377) output 1

Connect pin 5(MB3770) to pin 15(lm377) output 2

Connect pin 4 to the nearest Ground

For the caps im going to use positions R94 and C48 to make everything neat, Ive used C48 for the 22uf cap and R94 for the 220 uf cap. The Positive side of the cap will be towards the end of the board. Ok now you have to ground the neg side of the caps. The trace below the board convienetly joins the two caps so all we have to do is find the nearest ground and run a wire to it.

Connect pin 3(MB3730) to pin 8(lm377), this links to the 220uf cap

Connect pin 2(MB3730) to pin 9(lm377), this links to the 22uf cap

pin 1(MB3730) goes to pin 7(lm377) this is the input.

Run a green cap on each output line to ground you can see from my pic what i did. I stole the caps off a Tumble Pop board ;)

 

Your new amp is ready to go fire her up and if you get no smoke then you did good :D. I drilled a few holes in the pcb to mount the amp.

 

Just did the fourplay 4 in 1 hack which includes Galaxians, Super Galaxians, Galaxians X and Exodus and I must say SWEEET! Galaxians X is rather fun! See pics for the board with completed hack.

 

GET PICS HERE

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Xevios

 

Put these two repairs together because they are related.

Bought this board ages ago from E-bay which is a bootleg version of Xevious. I got the game working ok but the sound wouldnt work. I replaced the MB3730 amp booted her up but it would give me some ram error and the screen would be full of static and wavyness. If you removed the 12 volt line it would be fine. I thought this would be a simple fix but how wrong was I.

This game didnt really interest me so i got sick of wasting time on it and threw it on the "I'll get to it some day" pile.

Working on Galaxians and my retro fit amp I stumbled on the same problem when I removed a big 2200uf cap that ran from the 12 volt line to ground. Only reason I removed it was I noticed more modern PCBs used a 470uf cap with this amp and wanted to see what the difference was if any, I managed to recreate the exact ripple as Xevios had. Had a brain storm so after I finished my work on Galaxians I pulled out Xevious which by this time I had pulled parts off it. I managed to find all the parts ran a 470uf cap from the 12volt line to ground and hey presto working board with sound. So the cap running from the 12 volt line to ground is used to get rid of the ripple. I'm sure somebody non backyarder can explain it better than me.

Lesson learned ;)

There is a small fault I will get to one day where if you turn the voltage up to 5 volts the sound gets all messed up and random. Running the board at 4.5 volts it runs fine.

 

PICS HERE

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  • 2 weeks later...
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Galaxians Bootleg

 

Swapped this board for a Juno Fist. This thing was in bad shape board itself was fine but a lot of corroded chips.

 

Galaxians Bootleg

 

Bad 74ls138 @ 8M,P,N

Bad 74ls194 @ @L,K,L,H

Bad Prom@6L

Bad 74ls74 @ 6C, 5C, 6F

Replaced heavily corroded 368 and 107 at 1E and 1D

Other corroded chips: 5D,6N,3M,3R I'm sure theres others but cant remember replaced so many.

 

Up until now I've been able to get nothing on the screen except the occasional starfield and sometimes it even boots and plays. All you see is starfield and you can see where ship is shooting but nothing else.

I now have some garbage on the screen in the form of letters numbers etc and sometimes the game will boot and play. culprit was a 74ls157@3L.

Bad 74ls367@9D fixed some of the text in game and sprites.

Found a Bad 74ls157@2F I'm pretty sure this was what caused the double text and sparkles on the screen. Can't be sure because the game is going through Ram/Rom test then saying Bad Rom 3 then resetting. This I take as a good sign because before It was just random garbage and sometimes the game would boot and play. I'm suspecting one of the 74ls367s @ 5L or 5M I've been able to reproduce this on the other board when I was working on it.

I was right well mostly. The chip itself was fine but I found a burnt out trace between 5L pin 15 and ground. Board now fires up and runs. All graphics look great. Looks like the 157@3L was the problem with the graphics.

Colours decided to die, Bad 74ls161@3A special note: Only SS branded chips would work properly here all other branded chips I tried would not work 100%

This bootleg uses a rider board with 2 IC's a 74ls74 and 175 and 5 HM2510 rams. This board replaces the 5 27LS00 rams used on the original board. The Bootleg also is missing the 74ls174 that sits just above the 27ls00 rams.

These rams are for the Diving aliens without it you dont see any diving sprites but the rest of the game is normal. This board was in bad shape and when I plugged it in the text would all change to one colour. The 2 IC's on this board were corroded badly and I don't have any replacements for the rams if they are faulty. I decided to replace all the IC's and Sockets on the rider. This was a good move all the colours are now correct and you see diving objects. Only problem is they are split in half and the top part of the sprite is at the bottom also, at least they are the correct colour and working. This suggests the rams are ok so i need to look for something faulty on the board itself.

Found the problem a bad 74ls157 @ 3J Diving sprites and now 100% so relieved the rams were ok.

 

Time to add a amp to this old board and test the sounds. It looks like this board never had a amp put on it and was wired to run a external amp. There was one wire from where the volume pot should have been to where a cap should have been :)

Spending awhile gorking at where a amp was suppose to go I finally concluded this board would have used a MB3712 or MB3713 same chip just pinouts around the other way. These are very common on boards like Pacman, Gallag, Mr Do! etc.

Wiring the Amp up was easy, I just used a scrap bootleg Pacman I had on hand as reference. Need to complete the amp circuit was:

1x2200 uf cap

1X470 uf cap

1x47 uf cap

All caps 16 volts upwards.

3x104z mylars

a Volume pot.

and naturally the amp.

The pinout is slightly different for this amp. A common ground is needed for - sound and on the solder side where negative would normally go is where your positive line is Make sense? To keep the orignal pinout I jumped a wire from common ground to pin 5 parts side.

Fired the game up and the Amp works great! there are some sounds fault though :(. Only sounds present are the start up tune(if you can call it a tune), alien diving sound and alien explosion.

Missing is the background noise(rack movement), all you hear is a constant hum, the ships firing noise and the ship explosion which is different to the alien one.

Missing background rack movement was due to bad LM374 @ 7T

Missing explosion and fire was due to bad CD4066(Quad analog switch and mutiplexor) @ 7R

Diving sound was badly crackling changing a 470uf cap @ C37 fixed it.

Only other problem I noticed was the background Rack noise was VERY quite. Doing some poking around I tested the resistors around where the rack noise is generated namely the 3 455(normally 555) chips. found a bad 5.1k resistor @ R34 the resistor was reading 73k!. Replaced resistor and all is good.

Sound is now 100%

 

On a final note one thing I noticed about this board ever since i got the graphics working was how bright the display was, most noticable was the bottom 3 rows of aliens were a bright blue colour(see pics). I had a sneaky suspicion its was a group of resistors that sits below the colour prom at 6L. Turns out I was right. 3 of the resistors were the wrong value being 22 ohm instead of 220 ohm replacing these @ R74,R76 and R79 restored the colours back to what they should be....stupid bootleggers :P Its a shame in the pics you can't see the difference too well.

 

Just realised I lost most of my repair and PCB pics after I had to reformat :(

The Only pic i have of the PCB is one after I just started working on it. Missing is the big rider board with 2716s which holds the program for these bootlegs and I removed the Ram board.

I'm going to convert this board to Moon cresta using The Profs Hax

 

 

NOTES.

Found a few HM2510 ram equivalents that work.

 

Intel D2115A - Pacman Bootleg

Intel D2125A - Car Action

Hitachi HM2511 - Crazy Kong

 

PICS HERE

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  • 13 years later...

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