Put a DMM on one of the ROM power pins and give us an exact DC measurement of what you see there as compared to the power supply board's +5VDC test point. It is beginning to sound like a possible cable/connector issue.

Probably, but think about this: If you have some poor resistance point restricting current, the alternative 5v supply may be a shade higher current/voltage wise...so the restriction doesn't matter, but when you put in the OEM or Xpin and it doesn't work then. Does the alternative supply you are using power up the 5VDC on its own ?(not like you had it when feeding into the supply boards test point - but by itself)

One thing that may help us is some real numbers, some actual test measurements...accurate down to tenths of a volt and specific measurement points. Go with pin 1 of 5B on the CPU, its a 27128. Compare that with each of the supplies connected individually.

I have a DE Secret Service with the same supply, so if needed I can make some comparisons later.

Yes, something doesn't jive.

Mine is rock solid at:
5.04VDC. Test point, aftermarket PSU
5.01VDC on CN17 4,5,6
4.96VDC on 5B, 5C.

I've had that issue with one Sys11 game, which I think early DE boards are based on. In my case the game would always boot successfully the second time, without fail, and run as long as you like. There's a small filter cap I was recommended to replace, near the batteries. C27 on the wms schematic. That helped quite a bit. But like I said, my game was 100% stable every time on second boot... Don't know if yours is that way yet?

What are the status LEDs on the CPU board doing during power up and after the game freezes?

Any signs of former corrosion around the battery holder, or is all that perfectly clean?

Wow. Did you verify continuity of all the traces on this PIA? Sure looks like some possible breaks, and I'd be leery of it - especially if you didn't do the work, no telling how much heat those legs were exposed to from prior replacement. Also, how does the underside look?

If it were me, I'd remove that IC replace with a new socket while verifying each trace and connection compared to the schematics. Then install a new PIA and go for there.

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Cool, I'll keep my fingers crossed for ya...just take your time cleaning that up.

This solder job makes me feel sad. Using solder irons should be restricted by weapon laws.....

I want to mention this because I have owned two different TA's.

When I installed NVRAM in either of my TA games, it would not consistently boot properly. Once I put regular 6264 ram back in it, it worked just fine for years.

Not saying that is your issue but it's worth a shot if you get that PIA trace sorted out and are still having problems.

Worth noting that TA was the ONLY game I've ever had NVRAM issues with and I've used the different variations of NVRAM in at least 40 different games.

It never worked properly in either of my TA games. When installed, it would boot one out of 4 or 5 tries but all other times it would just be locked up and display some odd random digits on the displays, just as you described.

Hmmm, this is not my experience. Our Torpedo Alley is running fine with a FM1608 FerroRAM for many years. However, Data East CPU boards do have problems running Simtek NVRAM and ZeroPower SRAM (ST, Dallas) and need a workaround if you want to combine them.

Looking at the picture from the CPU board. There is a not-so-nice AMI brand 68A08 processor installed. These are well known to die slowly over the years. Not saying this is the cause of the bootproblem but it is certainly worth it to try another processor (6808, 6802, 68A09, etc.).

Possible, but being that the pin never worked in the new owners possession, I would suspect the prior rework first. It would be a different circumstance if the pin had been worked and then started to act up on its own. I think this one flaky from the start.

Sure....first action on this board is to clean up the butcher job around the PIA which drives the segments of the alpha nummeric displays.

Good find! Glad you got it going.