AVP no button panel power

[sstiglich]

Hi, all. I purchased an AVP machine with a 3.0 CPU in it. It had been in storage for a long time, and the previous owner had damaged the data cable going from the CPU to the backplane.

What I've done so far:

Replaced the 50 pin ribbon cable
Replaced the CPU battery (was in a boot loop)
Replaced the PCI card batteries (were not dead but low per a volt meter)
Replaced the telltale battery on the backplane (it had a tilt on this, and the battery was completely discharged)

I got an ekey and a diag key. Went thru and did a clear, then re-setup the games on the hard drive. The player button panel is completely dark, no lights and the LED buttons are dark.
The blackfin controller board is lit up, and it has one flashing amber light DS2 once the machine boots up. It shows two TILTS:

Button Disconnected and Invalid button panel.

I've checked all the cables, everything is seated properly and there are no obvious rips or other issues. The little 3.3V out board seems fine, but I have no way of verifying that.

My questions:

1. Does anyone know what the blackfin DS2 amber flashing light means?
2. One piece of documentation states "If the Low Voltage Detect is high (+3.3v level) the display will be blanked out". I appear to have good 3.3 voltage, and assume I would see a tilt onscreen if this was the issue?
3. There is a 4 pin cable that connects the blackfin controller to the 3.3 board, along with the HDMI cable. I assume the 4 pin is power, but I cannot find a schematic anywhere that labels the pins or defines what the voltage should be. Does anyone know?

At this point, I think the problem is either the blackfin board, the 3.3v board or the ribbon cable that connects the 3.3v board to the back of the buttons. Since I can see 0 evidence of cable issues, I am guessing it's one of the boards. Anyone got any troubleshooting thoughts or suggestions?

Finally, the only other issue I know of is the optical sensor for the belly door has a broken wire. I am ordering a replacement, but it's' not grounded out or anything else so I dont' believe it's related to my panel woes.

Thanks in advance for reading and any suggestions!

[sstiglich]

Just to follow up, this is solved.

It was a combination of two problems.

1) The ribbon cable that connects the 3.3v board and buttons was flakey. It still can't see any visible issues with the cable, but it would connect sometimes, and others not.
2) EVERY button was burned out. I mean no buttons would show any image, but the button did work when pressed.

Once I got a couple of good buttons and the cable, I could see signs of life and troubleshoot. I would like to thank RodneyK for the private messages and guidance. It was super helpful!