Hi all, I would like to humbly ask for help with, what I believe to be, a sync issue with my Dig Dug PCB.
Much of this hobby is still voodoo magic to me but I am learning and appreciate the deep knowledge on this forum.
Background on this game/issue - I purchased the game non working. It came with all the original parts with the exception that the monitor chassis was missing. Luckily I had a spare working GO7-CBO chassis. I put this on the tube and was able to get the tube to sync and display patterns with TPG. Overall, as far as I can tell, there have been no hacks, mods, or repairs to anything. I have worked through some edge connector and AR II issues, however I believe these are resolved now. The PCB boots( PCB red light on), game will coin up, there is audio, game plays "blind" ( there is audio, I can hear movement sounds from game when I press buttons and move stick, etc)
The monitor looks like this with the sync connector connected to the G07 chassis. It looks the same without the sync connector connected to the chassis.
According to my research:

Unfortunately I don't have an oscilloscope. I do have a logic probe, however I don't have a lot of experience using it. Just the same I have attempted to research sync issues with Dig Dug and located the following
http://www.arcaderestoration.com/RepairLog/15/Scrambled+video+ROM+issues.aspx This was inspiring so I ordered some LS369s, LS00s, LS74s, etc
Things I have tried to check:
- 4E(LS368) pin 3 is the output composite sync signal (CYSNC) from the sync generator circuit.
- I have continuity from 4E pin 3 to R87
- I also have continuity from the other side of R87/CSync test lug to the CSYCN pin on the edge connector (position "U" ; purple wire on harness that runs to sync pins on monitor chassis).
- My CSYNC line does not appear to be stuck low or high. Instead it pulses low and high at same time faster than the probe can probably keep with.
- As far as I can tell, none of the LS369 inputs or outputs of the sync circuitry are stuck low or high (I can provide more trouble shooting notes but this is getting long)
- I do notice an audible difference in the logic probes pulsing depending on the side of R87 I test from.
- 1) very fast pulse, with high and low lights on on but no yellow light - between edge connector "U" and the CSYNC Lug
- 2) less fast pulse audio, with high and low lights on, and yellow light blinking - when testing 4E pin 3 or from the other side of R87
- I realize "the sound" probably doesn't help and that a scope would be more ideal here.
- I also realize this probably has something to do with the resistor pulling the line
One thing that has me concerned is that my DMM shows continuity between edge connector "U" and the 10.6v line on the PCB when the wiring harness is attached to the board. I noticed this when testing continuity of the harness CSYNC wire from cync connector for chassis to harness edge connector pin "U". When the harness is not connected to the PCB I don't get continuity between 10v and the CSYCN circuit or between the harness CYSNC wire and harness 10,6v wire ("E")
My back can't take leaning into the cab to test anymore so I have a jamma adapater ordered and on the way so I can setup on a bench.
Thanks for reading this far

and thanks in advance for any tips or advice.