Introduction
The maximum current measurement capability of etracer is designed to be 300mA. This capability is more than adequate for testing and tracing most of common audio tubes such as 300B, KT88 and 6550. However, it might be desired to have a higher current measurement capability for testing tubes like 6C33C or KT150. This application note describes the modification method needed to increase the current measurement capability to 600mA. Below figure shows a traced curves set with a Telefunken EL156 with a screen voltage of 500V!! under pentode connection. Please note the maximum plate dissipation is set to 100W to allow traces in the high current region.


Traces of a Telefunken EL156 under pentode configuration with a screen voltage of 500V

 

Introducing the Sbox12 automatic wiring box for etracer. The Sbox12 is designed to sit underneath the etracer Model-01 chassis and performs automatic wiring for the users.

In the Facebook etracer group a member asked how important it is to supply a test voltage beyond 400V. Why can't we just test a tube up to 400V and extrapolate the curves from there. Well, besides the trivial answer that extrapolation is not reliable there are actually situations where extrapolation simply doesn't work.

 

The etracer software version 2.xx GUI

Introduction

The GUI (Graphics User Interface) in the etracer software is simple yet effective. The seven tabs below the curves plot area controls the operating mode of the software.

There are three tabs provide three basic modes of measurements: [Quick Scan], [Full Scan] and [Corners]. [Quick-Scan] is designed to perform a quick measurement around a quiescent operating point. This test is similar to the test performed by a tradition tube tester such as Hickok TV-7 with more parameters generated. The [Full Scan] test scans the plate-volt vs. plate-current curves at different grid bias and plot the result. The [Corners] test tests the DUT under extreme voltage conditions.

The [Combo] tab allows the user to compose a combination of three basic test modes and it has the ability to detect an insertion or a removal of a DUT. This mode is useful for testing a tube lot of the same type.

The [H-C Leakage] tab allows user to test the leakage current between the heater and the cathode of a vacuum tube.

The [Basic Params] and the [Load Line] tab allows users to perform real-time analysis of the full-scan data.

I am not sure since when vacuum tube testers like etracer are categorized as "pulse-type" tube testers. And this type of tube testers are usually being criticized as not accurate because the DUTs are not biased at the quiescent point and hence during testing the temperature of the DUT is lower than the temperature of the DUT in the real circuits. However, little information can be found on the accuracy requirement. How bad is it? And how much deviation is acceptable? 1%? 10%. In this article I will explore this issue a little deeper and measurement data are provided for references.