The RCA 50 ohm WECO type connector for broadcast patch panels has a .050" pin diameter.? The standard WECO 358A 75 ohm connector has a .090" diameter pin.? Both possess a .375" diameter barrel.? The mini-WECO (WECO 440) has a totally different barrel diameter (.298").? HP specifies a WECO 372A connector to fit the 124 ohm port.
It is worth checking to see if the 3506B has option 001.? If so, HP uses the 358A/75 ohm & 372A/124 ohm connectors.? The three units I have here all have option 001.? If it is a model with non-optioning (one of the more rare units from what I have found), the 75 ohm input uses the WECO 439/440A (mini-WECO), the 124 ohm input uses the WECO 443A, the 135 ohm input uses the WECO 431A and the 600 ohm input uses the WECO 310 (TRS plug).
And a word of caution on the 310 plug.? Although it looks like a standard 1/4" stereo plug, it is not.? Dimensions are different and the tip and ring are of a smaller diameter.? Pushing a standard stereo plug into the jack on the unit will most likely either distort the jack contacts or damage them requiring replacement of the jack..
Greg
