Gallag board needs help

Hi guys,

Got myself an untested bootleg Galaga. Same as what's seen at the very bottom of this page (https://wiki.arcadeotaku.com/w/Gallag_Repair_Logs). Spent some time last night wiring up a Jamma adaptor, and after some initial issues with bad ROM messages, I reseated all the ROMs and was able to get the board to boot.

 

Unfortunately all the sprites are funky and seem distorted and repeated/stretched across the entire width of the screen, and the credit words are duplicated running vertically on the left side, from bottom to top. The grid also is not right.

 

See here:

 

https://scontent.fakl7-1.fna.fbcdn.net/v/t1.0-9/29694678_2045916382090034_6205322485601478122_n.jpg?_nc_cat=0&oh=283085e943b0db029db9a0bdf8df8736&oe=5B414359

 

https://scontent.fakl7-1.fna.fbcdn.net/v/t1.0-9/29684090_2045916385423367_8707190020004783836_n.jpg?_nc_cat=0&oh=441243a0ca32d61bbf6279d304a753bd&oe=5B3E5106

 

I was actually able to get the board working briefly, but only once. On power down, and power up, the board was all screwed up again. I thought this temporary 'fix' had to do with reseating the 6116 (the only other IC that is socketed apart from the ROMs), which I had just done before the sprites came right, but further reseating and cleaning the legs of the 6116 does nothing. I've also swapped the 6116 to no avail, so I think the issue isn't with this RAM, and possibly not with the RAM socket either...not 100% sure of that though.

 

I have also removed, swapped around the ribbon cable positions and multiple times in case there is a bad connection here, but didn't change anything.

 

Anyway, I'm stumped and thought someone here may have some good advice.

 

Cheers

 

Philip

fixed : 74LS02 @ A3 on video (bottom) board

Well done on the repair and thanks for sharing.

What brand was the 74LS02 that failed?

Fujitsu

lol didnt much see that coming

lol didnt much see that coming

 

:lol

 

Yeah it was the first thing I thought.

Fujitsu components have a bad reputation?

Fujitsu components have a bad reputation?

Yep. They fail quite often.

 

Sent from my SM-G930F using Tapatalk

The seem to be a very common failing part nowadays. They give me nightmares.

 

I've repaired several Konami boards that are loaded with these. They tend to fail one after the other whilst the board sits on your bench during repair adding to your existing problems. My last Konami board had at least 15 bad chips, 12 of them were all Fujitstu.

 

Replacing them all is a good idea.

I've been told 2 stories...

 

1 was that they have problem with the formula used for the plastic body that caused corrosion internally on the die wires

 

2 was that they used bad wire for the die wires

 

Neither of those stories account for the high number of stuck gates or chattering gates that I've run across. They only account for the totally dead gates.

I always assumed that the ones doing crazy stuff (but not floating) had lost their true 5V or ground bond wires, leaving the internal logic driven by parasitic voltages taken from the logic input or outputs. It would be interesting to see a dead one decapped, but as I suspect the wires fracture from knocks and bumps after years of corrosion, I doubt one one would survive the decap process itself.