Break Thru repair log

RedlandMan

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Purchased pcb not working off Ebay. Pcb had sound and would sort up boot up but no game play with scrambled graphics and screen would flip upside down . Found top board top have some corrosion. Cleaned visable corrosion with fiberglass tool, replaced sockets to roms DD01 and DD02 and removed dip switch band 2 until i ordered a new one. Very little difference on graphics but screen not flipping. removed and checked roms found bad roms at same locations where i change sockets.Burned new roms. Graphics got better but if you tried to play a game it would go to a check screen saying bad ram at location B11 top board. with a logic probe found there was a floating line on the ram input coming from IC A13 found the 74157 had good inputs but no output. Replace IC now board had better graphic but if you tried to play a game after 4 or 5 seconds game would reset. The IC under the one i changed was very rusty and found 3 floating lines on it. Replaced it but found input Q was dead due to corroded trace on board. Jumped it to the ic next to it and board works perfect. Without the corrosion to guide me i would not of been able to fix this pcb since there are no shcematics available.Hope this helps someone. Luis
 

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