Quoted from IMI4tth3w:

So i took some time to look over a stern node board on ghostbusters. I don't see what is so unknown about it? Sure its got surface mount instead of traditional pinball through hole style, but anyone with some technical know how and a multimeter with continuity testing can figure out whats going on. Oh and google to search case numbers on parts.
There's a microcontroller at the heart. The small flat flex connector in the middle is a programming header, but there are also 6 pads on the bottom that share pins with the flat flex connector for bed of nails programming to make it easier for programming during manufacture.
The communication is UART over half duplex RS485. They also use optocouplers to isolate the RS485 ethernet cable to eliminate ground loops. From what i googled they are using 48V (maaaybe 12V or 24V) over the ethernet cable with a 5V voltage regulator on the isolated side to power the rs485 ic.
There's a 6V 3A regulator to convert the main 48V input for the lower voltage parts and lights. Some additional filtering and regulation is also there to bring the 6V down to 5V for more sensitive components.
Shift registers are used for switch inputs and DC light outputs. And there's an SPI light bus header output for the individually controlled lights.
Last there is some mosfets for the solenoids that use inverted schmitt triggers as gate drivers. A couple microcontroller pins drive the schmitt triggers/mosfets for PWM control.
I'm not going to make a full schematic, but i've been able to find a datasheet for about 90% of the parts on this board.
Its actually a great design and well done. The whole package is very neat and well laid out.
Now what i'm wondering, is even with full schematics of these things, i don't think these old school pin ops are going to be doing SMT rework. And the ones who are able to SMT rework, from what my searching has found, have been able to figure out what they needed to do anyways. (found a guy who shorted a light and blew a small output transistor and replaced it himself on a stern node board).
I have not look too in depth at the main CPU, but it seems pretty similar. One main 48V input with some voltage regulation, an audio amplifier stage, etc.
Let me know if you guys have any specific issues or questions about these boards. I have yet to find any real information about their failure modes as almost every single post i've seen here about a "failed" node board is completely ambiguous, to the point where its impossible to know what actually failed.

Quoted from KenLayton:

In the Spike system, the cpu board as well as all the node boards take 48 volts input and regulate it down to 5 volts. So you could have a bad node board.
In my opinion a design that takes 48 volts and drops it down to 5 volts is a recipe for disaster. They should have used a seperate power supply unit or board to provide 5 volts and leave the 48 volts just for operating coils.