In order to replace the resistor, I think I'll need to remove everything so I can access the back:
On instruments with serial numbers below B040909, examine the circuitry near A10U802 (the Horizontal Preamplifier IC, shown on diagram 6) to determine if a diode (CR801) has been connected between C816 and W804. The anode of the diode connects to the end of C816 nearest pin 9 (-5 Vcc) of U802, and the cathode connects to to the end of W804 toward the rear of the instrument (the horizontal RO input—pin 1 of U802). For static discharge protection, the diode must be in place or added (and left) to the circuit before disconnecting the ribbon cable to J2302 on the Processor board.
I think I already removed that ribbon cable while reseating it. Could that be the cause of this issue? And now that it happened does it really matter where I put that diode in or not? I'm not sure how I would install the diode without access to the back of the circuit board
