Galaxian screen scrambled.

Holleywierd

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Hey everyone, I thought I would throw an issue out there as I've tried as much as I know about to fix it with no resolution. So I have an original 1979 Galaxian. Turn on the machine without the pcb and it shows up, bit of burn in but works and switch it to test mode then the RGB line down the middle of a black screen shows up so guessing that's a good thing. Well I bought a refurbished working PCB and tested the slot pads where the connector goes. It says A on one side and Z on the other end. It was reading 4volts. I think I read it needs to be 5v but I have no idea how to change that. So I turn it on with the board connected, then the sound pot on the pcb works but it is a loud buzzing and scrambled screen. I tried setting dip switches to various free play and bonus settings with no luck. There is a 6th dip switch that does nothing I'm assuming. Also, another thing I tried was the fuses on the transformer board. They all work but one, but that one has black wires going in and out on both sides so guessing it's a ground passage? I'm sorry but I'm amature at best when it comes to repairing these. I know a little about electronic repair but this is all foriegn so please feel free to point out the obvious or any new suggestions. Thanks guys!
 
Ok, I am not sure where that one is. Would it be on the pcb or connected to it? Found a pic and doesnt look similiar to mine.

You can hook a switcher up to that board for bench testing. I have seen some very bad ways to do it. I used a connector from a computer to go to the drives (cd rom, hard drive, ect) and solder it to the diodes, +12 goes to the cathode of the smaller diodes closer to the audio amp. The +5 goes to the larger diodes near the regulator and there is a large white resistor you jumper near the bottom left of the board. You can use this and put it in the cabe so it will work either way. You only need to remove the jumper for the resistor for the cab. I have had a problem locating the rom files and the ones in MAME don't have all of the files, u,v,w,y,z. A fellow KLOV member gave me the files so if you need them I can send them to you to verify the rom files.

Before you do any more testing, you have to get the voltages correct at the chips and should verify the roms.

Mine had a problem with watch dog always barking and there is a pad to disable the watch dog. I though it was one of the 74ls138's but at the Crab Town arcade party Orion3311 pointed out a 74ls245 that should be replace first. I replace the 138's with help from Buffett and no joy at the End of Line arcade party. I aske Buffett if he could replace the 245 and the game booted and played fine. Buffett put in the old 74ls138's (they arrived at the party from Riptor via Major Havioc) one at a time to see if which one was bad since there was sockets put in. They are still in the board and working.

I now have a working board so if you need some pics or certain points probed let me/us know. I also have some daughter card if you need one and they hold the roms mentioned above.
 
Thanks for the info there. Sounds easy but I don't have the tools to test all the roms like that. Do you happen to have a pic of the daughter board? If you have one for sale, how much you thinking? I got a tech coming out to look at it in a few weeks, but gathering parts needed possibly while I can. We seemed to have thought it was the monitor caps at first, but it runs fine as far as I can tell. Would a bad fuse on the power supply possible do this?
 
Thanks for the info there. Sounds easy but I don't have the tools to test all the roms like that. Do you happen to have a pic of the daughter board? If you have one for sale, how much you thinking? I got a tech coming out to look at it in a few weeks, but gathering parts needed possibly while I can. We seemed to have thought it was the monitor caps at first, but it runs fine as far as I can tell. Would a bad fuse on the power supply possible do this?

Not usually but that can cause issues and that board takes ac voltage so a fuse doing that is very unlikely. It could be the diodes are leaking but again very doubtful. I am fairly certain you have a board issue and if you probe pin 26 (reset pin) of the z80 processor it will probably be barking (hi lo) when it should be high. There is some pads on the board to disable that but should be left for the tech.

check out this thread. It has some info for a rom hack you might want to look into after you get that board going.

http://forums.arcade-museum.com/showthread.php?t=182173&highlight=galaxian

and here is a board on fleabay with the daughter card....

http://www.ebay.com/itm/Galaxian-PC...350?pt=LH_DefaultDomain_0&hash=item3cc30be8b6

If you pm me your address I can send you a daughter card but the one you have should be ok. Let me know if you need one or want to trade or what. I thought my rom burns were bad but it was just a single chip a 74ls245 at the top left (with edge connector to your left).

P.S.

What an ugly baby; and there aren't many of them but that is certainly one.
 
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That's my baby pic haha. Nah, its from the show Tim and Eric, some random thing that pops up named chippy. Well I will take a better look at my board and see if the tech wants to try a new board after a few other things so I will keep you posted. Thanks again!
 
That's my baby pic haha. Nah, its from the show Tim and Eric, some random thing that pops up named chippy. Well I will take a better look at my board and see if the tech wants to try a new board after a few other things so I will keep you posted. Thanks again!

If you need more help just ask I have a few of these board and some bootlegs That are about the same.

Ohh, My pic is of Mr. bubble A bath soap I used to like as a kid.
 
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