stern pinball Logic repair

[salviador]

Hi, I'm fixing a stern pinball Of the 90's.
The pinball work but I have a problem, The cpu resets.
I connected my logic analyzer in the bus I noticed that the D2 is sometimes dirty, I've changed some 74 ttl logic but But I did not notice any improvements
Why the D2 databus is dirty?

[Andy Watson]

Are the power supplies clean?
I have seen similar "random" logic changes due failing ground connections - due to poor vias and sometimes cold-joints. Check the power on the actual pins of the ICs.

[salviador]

Thank you Andy!

My question is why only Data2 and not in other Data bit.

[Andy Watson]

My question is why only Data2 and not in other Data bit.

I think my earlier answer is still valid. However, consider also: Your logic analyzer is telling you either 1 or 0 - it may be that the signal is at an indeterminate logic level - either because it is tri-state or because it is conflicting with an output that is not properly releasing the bus.

[stj]

so what board is it?
got any photo's?

most problems like this are caused by bad chip sockets.

[salviador]

send photo

[Pinkus]

looks like you are using an Intronix Logicport. Did you try to raise or lower the logic threshold a bit? Maybe you are juuuust out of the valid range.

[salviador]

looks like you are using an Intronix Logicport. Did you try to raise or lower the logic threshold a bit? Maybe you are juuuust out of the valid range.

Yer I try:
3.00v
2.50v
2.30v
2.00v

[grumpydoc]

Some notes here http://www.pinballsupernova.com/images/Sega_Stern%20White%20Star%20Repair%20-%20PinWiki.pdf

I presume you have schematics

As ever, start with the PSU rails

[DaJMasta]

Do you have an oscilloscope as well?  Hook up a probe to the dirty line and a few to ones that seem to be good and see if there's a visual difference (or another working line and a rail or two).  Could tell you a lot about the source of the problem.

[edavid]

Did you try swapping the CPU?

[Pinkus]

Do you have an oscilloscope as well?  Hook up a probe to the dirty line and a few to ones that seem to be good and see if there's a visual difference (or another working line and a rail or two).  Could tell you a lot about the source of the problem.

that is probably the best way to proceed

[salviador]

I changed 80% logic, worked for 10 minutes and then as before