Atari Gen2 MPU - general electronics question

Laschek

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I am trying to bring back to live an Atari Superman pin.
While preparing to test the MPU board on my bench with the Leon test ROM I discovered that the +5V and +12V rails were connected.
Turns out the big resistor (?) on one corner of the board was shorted:

atari_mpu2z3urq.jpg


Unfortunately the game was powered up last year, so I assume that many chips got fried due to the fact that they got 12V? Or what exactly happens when the board is powered up while the +5 and +12V rails are connected? Do the voltages add up?
But my main question is (as I am trying to learn as much as I can): why are the +5 and +12V rails connected with a resistor anyway?
Here's the part from schematics:

ataripingen2powerinputtuy5.png


Unfortunately the markings on that resistor are illegible and the manual does not match up to the real hardware. The schematic shown says 10 Ohms 10 Watt, does that value seem ok for the depicted part?

Thanks!
 

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