760 D intensity doesn't work


Hi Tek folks,

Working on a 760 D, when I got it the power supply was cycling and the high voltage would not come up. Lifting the output of the quadrupler let the low voltage supply come up, so I assumed it was bad. Bought a 1710B and a 1720 for parts off of eBay for the quadruplers. Swapped the quadrupler out of the 1710B and still had same symptom. And now the low voltage won't come back after pulling the swapped quadrupler. Oops, somehow took backwards step. So pulled entire power supply from the 1720 and swapped in. Now 760 powers up but trace super bright and intensity control on the main board does nothing. I did check for continuity from the intensity connector pin going to the PSU, and can see the resistance change from the pot to ground. Z-axis amp trouble?