Hi,
I've gotten quite a bit of help here with my dead cluster and have dug into it quite a ways but I need a reality check.

Here is what I know:
1) All dash warning lights and gauges are dead. The OD indicator arrow is on and will switch off when the button in the shifter is pushed but this setting is not retained when key is turned off. Fuel and temp gauges are also dead.
2) Car starts and runs normally. Starting the car doesn't get any of the lights or gauges to work consistently. The "battery" light for the charge system has come on a few times but not consistently. It seemed kind of "flickery". It currently is not coming on.
3) Autozone's test machine says alternator (including voltage regulator) is fine.
4) I have power at the blue wire in the three wire connector at the back of the speedometer when the ignition switch is on. Current is getting from this connector to the circuit board it connects to.

Here's what I am thinking. Please let me know if I am missing something or am off track. I'm getting better at figuring out my Bentley wiring diagram but am not good yet.
1) Since both the gauges (fuel and temp) and the warning lights are dead, I've ruled out problems with the grounding system through the alternator. As best I can tell, the gauges ground through their senders so it doesn't seem like problems at the alternator would shut them down too.
2) This leads me to suspect a problem on the supply side, but as I said, current is coming in on the blue wire to the speedometer and appears to be getting to at least the connector on the circuit board. Is there another wire I should be checking for power coming in?
2) I'm beginning to wonder whether there is some kind of problem within the cluster that is interrupting the current. Are there any common failure points internally?

Thanks for your help and patience with this. It's beginning to get frustrating.