Agilent 8753ES A21 Test port coupler repair

[jjoonathan]

Yes, there is a third resistor R3 near the other two that connects the outer conductor of the beaded coax to ground. I believe it is directly beneath the coax, although some designs (the newer Keysight patent and the Anritsu design) place it on the same plane as R1, R2 but on the opposite side of the coax landing pad. It should be about 9.417 ohms.

[AJ3G]

Good Info - Let me put it back under the microscope and see if I can locate it. Considering the other two were blown wide open, I suspect this one too is a problem. Now I just need to find it.

[AJ3G]

I found the final resistor. It too was wide open. I have included the RL response of the bridge. For R3, I have tacked in a 10 Ohm resistor for the moment. I am hopeful when I put in 9.41 Ohm in place of R3 I get a better low frequency response. I think this is a pretty good result.

Rich