Author Topic: thoughts about component tester built into Heath scope aka Octopus curve tracer  (Read 1990 times)

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Offline festusTopic starter

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Hi guys,

I've been recently inspired by watching Mr Carlson's videos and his signature tracer.

Hopefully some knowledgeable experts here could comment about the safety-against-damaging-components aspect of the built-in component tester in my Heath SO-4552 Oscilloscope. 

The RMS voltage and current is significantly higher than that of the typical Octopus circuits.

Here are the specs, so please let me know if this risks damaging components:

Test Voltage: maximum 6V rms (open circuit)
Test current: max 11ma (shorted)
Test freq: line freq (aka 60hz)

So basically I am wondering whether the 6v rms and 11ma are risky.  The manual suggests that it can be, saying:

"transistors used in high-gain low noise applications may be permanently degraded when subjected to a B-E reverse voltage that exceeds breakdown rating.  The component test open-circuit test voltage can be as high as 9V peak. This voltage can be reduced by resistive loading or zener clamping diode to permit safe transistor testing."

Any thoughts?  I'd like to use this, since I already have it, and it's built-in.  The scope is rather cheap specs, though, only having a vertical down to 5mv, but otherwise suffices for my basic needs.

« Last Edit: January 16, 2019, 05:33:44 pm by festus »
 

Offline Paul Rose

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If you haven't already, check out these older threads:

https://www.eevblog.com/forum/testgear/inexpensive-curve-tracer/
https://www.eevblog.com/forum/beginners/installing-npn-transistor-backwards/

9V will exceed the reverse B-E rating for many (most) transistors.  Whether it will actually do anything is harder to say.

However, you already have the tester, and jellybean transistors are cheap.  Play with some and see how frequently you actually see B-E current in the reverse direction.  You will gain some confidence.

You could use a simple diode across the B-E connected opposite polarity from the natural B-E diode for protection.  But it means being aware of what you are testing and how it is connected.
 


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