Saintummers Projects


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Isotest kit is sold out as of 11.10.2022.
I will gladly accept enquiries for a possible new edition of the kit via mail
A complete kit (This page was last updated in March 2021) with all parts is available. Please inqire by the Author.

The Isotest6a was developed by Mr. Gerhard Heigl, Herzogenburg, Austria


Insulation tester

It is a high impedance (10MOhm) voltage source with which capacitors are checked at nominal voltage.
the voltage range is 20-500V. The measured resistance will be given in MOhm. A good capacitor has a value close to infinity. Only a test with nominal voltage detects the failure of capacitors, which can still show good values with a modern component tester.

Note that component tester or a multimeter only use 5 V for capacitor measuring. Therefore, every capacitor is good, but still unusable in tube circuits. This was the main purpose for developing Isotest6a.
It is not possible to test electrolytic capacitors here because of the high internal resistance of the voltage source. On the other hand, you can safely touch the test clamps here. With an HV power supply, I don't want to do that.

My job was only to adapt the print to the components available today and make the kit available again to meet the high demand for it.
Kit with all parts are available from the author Please inquire by mail
All rights to the isotest belongs to Mr. Gerhard Heigl, Herzogenburg, Austria.

The original documentation (german) by G. Heigl for the Isotest6a is available
More information can be found here
These pages are the foundation for the building instructions.


Checking transformers, rectifiers, capacitors, etc.
Article in by G. Heigl




Parts side

Finished board

finished board

Interior views

internal wiring, solder connections with shrink tubing protected against breaking.


The battery is upright in the device.


Building instructions and descriptions (english/german)



Isotest6a Kits with all parts are available. Please inquire by mail
====== Detailed building instructions as PDF =====

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H.Stummer Dateidatum: 11.10.2022