Situation report: Williams Blackout. LED's flash once on power up then stay off, however, game does not go into attract mode. I have seen it go into attract mode once, so I know it can work... when I press the test button it always gives me the 'lower LED stays on' error code, meaning there is a read write error on the 6810 RAM chips...
Replaced 40 pin interconnect
Replaced 6810 RAM and sockets
Replaced rom sockets (minus IC14 which looks good to me)
Replaced loose IC10 PIA chip slot on Driver board
Tested all voltages from PS to connectors on Driver and MPU boards (have not tested voltages after they get into the driver board or MPU (can't make heads or tails of the schematics, the other Bally machine I have has clear test points and values, Williams Sys4 MPU schematics don't seem to. Maybe I'm looking at the wrong one [Phoenix] maybe I just don't know what I'm looking at...)
Note to self: Self, check other sys 4 MPU schematics (as we don't know which game our board is actually from originally)
MPU board is system 4 (Black out is system 6). Previous owner says it worked fine for many years (besides issues with blowing SOL fuses...) so I'm not too worried about compatibility here and I read that sys 4 updated with a socket in IC14 is fine for running sys 6 games. However, there could still be a compatibility issue here...
A few sockets on MPU and Driver boards were replaced, but not by me. Continuity tests fine, but these are still on my list of things to check if all else fails.
So... I feel like I have given a decent try to bulletproofing the relevant weak points and nothing has gotten me into attract mode yet.
I have a Logic probe coming in the mail tomorrow and have been reading about what the heck to do with it... but I am sure I will need some help.
Questions so far:
Q1: how do I tell when I want the probe on 5v and when I want it on 12v, is it as simple as IDing the chip in question as TLL or CMOS? Are there any tricky spots to watch out for where there will be a 12v output on a 5v chip?
Q2: What the heck am I testing for?
Q3: And where do I start?
I think I want to make sure each IC is getting the power it wants (usually 5v on pin 1?) and that its ground is reading 'low' and pretty much all other legs should read a pulse (or match input to output)???
Am I basically looking at a data sheet for each IC in order to know what to expect from what leg?
Thanks guys, sorry I'm so clueless here... if anyone can point me to some relevant reading/video I'm glad to read up... Here is what I have been reading already:
Reading through the examples on this home pinball repair link is making things start to make sense... but none of the examples are for troubleshooting boot issues, so they don't get in to IC stuff much. That is specifically the area I feel I need help understanding.