Another way to do it is to make the main board such that there is a straight shot down from each of the 4 connection points on the HRM board. Mine will be suspended by 3 straight jumper wires and an inline resistor. If you hook it up with a cathode follower, the test point gives the plate voltage of V2B.tubedogsmith wrote:What's connected to the wire loop on the HRM board? Is there room under those pots to get a lead in to measure them?
If you hook it up the other way, then the test point gives the b+ voltage for V2b and would be no different from what you would measure off the power supply board. Just my guess and 2 cents.
https://tubeamparchive.com/download/file.php?id=8316
