Exed Exes Repair Logs

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Repairer: Arcade King
Forum Thread: Exed Exes PCB Repair

This top info was one of the first boards I ever tried to fix second one is recent

Got this one going today. Bought this one with a bunch of 8 faulty boards off E-bay and I'm happy to say this is the second last faulty one

Problem:Game would reset after the title screen after much stuffing around I found lowering the voltage to 4.4 volts would get the game running but there was much static on the screen specially in the middle scrolling section.

Fix: Short version Bad program E-Prom on top board at 11M. even though this rom verified and passed tests on my programmer it was the cause of the resetting on the board. The legs on the E-prom were clean and corrosion free, I'll try erasing it and reprogramming it when ever i could be stuffed. I'm just happy to have a working board of this awsome vertical shooter!

Side Note: I've been working on and off in bits on this board for months. There was a stupid problem with the game where in the demo screen it would flash 5 times at the start. Turns out there is a bug in the game where if you press the second fire button it will let off those "smart bomb" thingies even in demo mode!. I tested this on mame and its exactly the same. Turns out it was my own stupid fault, when I put new buttons in the cocktail I connected the wire to the wrong micro switch pin and the button was always on. I pulled a lot of IC's off trying to find the problem and turns out it wasnt even the board which completely threw me off track of the bad E-prom.

Board 2 identical bootleg to board above.

Top Board
Problem: No sound except 1 continuous hum. Fix: 74ls138 @ 9B pin 15 output dead.

Problem: Screen all messed up sparkles every where only title and highscore clear. Fix:74ls174 @ 2F

Exed exes sparkles.jpg


Found another 74ls174 just above that was stuffed to, replacing it I could see some sprites down the bottom of the screen with lines in them.

Exed exes bad sprites.jpg


Bottom board
Problem: Middle ground green hexs was wrong, right half of screen was displaying correct left was wrong. Fix: 74ls174 @ F1 on bottom video board.

74ls157 pin 7 stuck low replacing it made sprites move at bottom, sprites still have lines through them and stuck at bottom. 2 more bad chips 74ls 174@N10 and 74ls157@n12 sprites look a little more filled in now but still stuck at bottom.

Bad 74ls163@N5 Outputs were all stuck low. Replacing this the sprites are mostly 80% complete but still stuck at bottom. The chip below the one above is also bad another 74ls163@N6 output pin 11 stuck low, now the sprites are moving around the screen but they look like they are split half of the sprite still stuck down the bottom and half moving around the screen. The 74ls163 below that was stuffed to @ N7, graphics are now looking much better. There is still a problem though. There are like invisible bars running down the screen and when the sprites pass through them they turn invisible.

Exed exes bad sprites 2.jpg


Found the last chip that was causing the invisible lines, 74ls283 @ E12 game looks great!

Problem: Found another graphics problem. The lower background was slightly messed up(see pics) fix was a 74ls74@N1. Just found one last small fault. In the large sprites eg: big explosion when your ship dies and the big strawberry had a small black line through them. Fix: Dead output on a 74ls283 @ F12 pin 4

I can't tell you guys how much easier having a working board to fix a fulty one helps. In the case above I plugged the top board in with good bottom board found the faults fixed them then moved to the faulty bottom board.

Forgot to mention that all bad ICs were F branded Fairchild chips. These chips are the devil. On most of the boards I have worked on 98% of the time these brand chips have be the ones that failed. Can't complain but they have lasted over 20 years.


Repair Logs converted to wiki format by Brad from Aussie Arcade.