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Greetings Programs,

A few weeks ago I picked up a dead Asteroids cocktail table and I'd like some advice before I proceed any further. PCB SN is 199086 -05 and monitor is a G05-805.
[Note: This is my first real repair challenge. I'm still a newbie but after pouring through this forum I figured I'd ask the professionals. If this post has too much information please throw your digital tomatoes at me]
Before I begin, I'll admit that I made the rookie mistake of turning the game on with the monitor plugged in before testing any voltages or anything. What I noticed, though, is that the monitor's spot killer LED is on and there is no neck glow.

Prior work to the board (by the looks of it):
Somebody added a daughter card (I assume speed mod) at C5 jumped to N11 legs 2 and 13
The DAC at B12 (Y voltage) was replaced

Things I've done so far:
Cleaned the inside of the cabinet
Replaced power cord
Replaced bad 3A fuse at F6
Replaced 2N3055 (preventative)
Checked voltages on AR1: good 6.2v with no board so 5.24vdc with board at +5v and 11.90 at 10.3v unregulated (No AC ripple: 0.05vac at 10.3 unregulated)
Cleaned and Deoxited edge connectors
Tested voltages on board: 4.94v at +5v and 4.92v at CPU pin 8
Checked that CPU is getting clock (it's there but unsure if correct speed)
Replaced bad CPU (pulled from working Missile Command)
Cleaned, Deoxited and reseated PROMs and made sure they're in the correct order for rev 5 (although E/F2 gets very hot to the touch: is this a problem indicator??)
CPU is watchdogging in attract mode but in test mode the tones tell me that RAM at N4 has failed
Tested voltages at the following regulators:
VR1: 24.17, 11.97
VR2: -25.08, -15.50
VR3: 24.16, 5.03
VR4: 24.23, 14.72
[All outputs listed above look pretty good based on the schematic]
Tested voltages at DACs at B12 and D12 and they look good compared to schematic, as well as the following chips up until the X and Y outputs, which are -5.09vdc and -10.28vdc respectively in test mode. Neither have any AC voltage.
Shotgun replaced the op-amp at A13 because I have a bunch lying around (no change)

Where I'm at:
If I'm overthinking this whole thing please let me know. I assume that the monitor was fudged when I first plugged the game in because of the X and Y output voltages. I'm going to order a couple of RAM chips in case others fail. Should I replace the DACs? since the Y output is much higher than the X (which also isn't good I think) I assume the original DAC replacement failed. Where should I go from here? Any help/guidance would be greatly appreciated.

[Postscript/funny story.... I have a Nicolet Pro 20 oscilloscope. I thought I was learning how to use it/diagnose this board with it because it has an X/Y mode and whatnot. Turns out the stupid thing is only 1mHz. No wonder I couldn't see anything!]
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