Sky Adventure PCB, wire running under a 74ls161ap

ifkz

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I ordered this PCB as non-working. Odd activity, it passed all self tests, had full sound and gameplay, perfect sprites...until about a minute of play and the game would crash. I tried all of the easy things and found this one bare wire on pin 1 of a hd74ls161ap running under the chip. I pulled on it, looked odd and it moved easily. Got the other end from under the chip and now the game does not boot. Any idea one where it should go?

A datasheet on this chip says the wire is soldered to "Clear" It is a ...Synchronous 4-bit Binary Counter. Manual is no help.
 
Figured out where it went, to "enable T"...whatever that means. Still no worse off than before, perfect screens, and crashes a little bit into the game. All tests pass.

Never had one like this, next step will be to verify the program roms with romident...corrupt data could be causing a crash if it is in the program section...

Anyone else with a thought???
 
Even though the 68000 was actively running code? I've never seen a 68000 fail, if the program EPROMS are good, I guess I'll swap it out with another.
 
Faulty 68000s are rare, but that doesnt mean you dont have one. They are phenominally complicated chips so fault in one region could cause it to crash at a certain point. The question is whether it crashes at that point because that is the point in attract mode it gets to after X amount of time on, or whether there is anything specific about that point that is causing the crash directly.

I had a fault on a Moonwalker board where it would run through the first two levels and then crash when the walls of the ammusement arcade rolled back. It could be that that section used an opcode that had not be called until that point, or as it was a Sega board it could be that it hit the very first occurance of bitrot in the encryption table in the FD109 CPU which is a 68000 core behind some battery backed RAM holding the encryption table.

Its all a bit theoretical but if the 68000 is socketed it is very easy to swap in another chip just to rule it out, no matter how unlikely the fault is, if it is easy to rule out then you might as well.
 
Well, I've got nothing to lose at this point, I'll swap in another CPU and a socket (the original is soldered in) when the weather warms up enough. If that does not fix it, I will also pull the other added socket to look underneath and see if the previous tech screwed anything up during the install. Seems to be a rare game to find working, most everything in past for sale posts here had problems.
 
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