Heathkit V2A – Vintage VTVM (Vacuum Tube Volt Meter) – Repair n Restore

This was just for fun, not a serious project. As per info online, it’s supposedly from the 1945-49 era. Fortunately for me, someone donated it and the only part that I was interested in was the fact that there is no schematic available online. And no surprises here, the condition was also not that good.

This is how I received it.


And this is after restoration –


So I here is the flow of events in a video, including the side by side performance along with HP/Agilent 34401A 6.5 Digit Meter 😉

Video #1 – Heathkit V2A – Repair/Restore


Also, I traced the schematic and attaching it here.

Heathkit V2A Vacuum Tube Volt Meter (VTVM) Schematic


This is a 4A schematic I updated to reflect the changes for  2A. There are no major changes, other than a few missing resistors, changes in resistance values, and a missing AC Balance Pot.

One major change is the use of 6X5 as rectifier, instead of semiconductor in 4A. I have identified the changes above in RED.

8.3 Ohm Resistor in the battery circuit was bad, I used a 47 Ohm and 10 Ohm in parallel to arrive exactly 8.3 Ohm. I had to try few 47 Ohm resistors until I could get exactly 8.3 Ohms to get the right value within tolerance window.

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