wrong DMM Led diagnostic...

Zener_Diode said:

Hey

https://www.electro-tech-online.com/threads/vcr-philips-problem.24438/

When I checked the LED with DMM it shows me that the LED is good.
When I replace the old LED by the new one the VCR stated to work properly.
How can it me, the DMM shows that led is good while it is bad???

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Nigel Goodwin said:

All the DMM checks is if it's O/C or not - it doesn't mean it actually works!.

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Zener_Diode said:

What is O/C?

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How can I check the components and to know that it works for sure?

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Zener_Diode said:

Hey

https://www.electro-tech-online.com/threads/vcr-philips-problem.24438/

When I checked the LED with DMM it shows me that the LED is good.
When I replace the old LED by the new one the VCR stated to work properly.
How can it me, the DMM shows that led is good while it is bad???

Click to expand...

Nigel Goodwin said:

You place it in a circuit and confirm it works correctly, that's the only 100% way.

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Tarsil said:

REading the other post too I'd say that LED doesn't have enought voltage to operate. 1.5V...I haven't seen a LED that can be operated from a single aa batery. So the LED is OK but it doesn't give any light. U should consider replacing the resistor before the led. What value does it has now?

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Zener_Diode said:

It is an infrared LED I can't see it's light.
If I connect it to 10V through 10K resester I have 893uA current, 1V fells on diode.
if I rise the supply voltage the current rise too but the led voltage don't changed.
how can I know that he is good ot bad???




I don't remember exactly but I think there was a 76 om resester. 5V before resester and 1.5V on the led. When I put other LED everything started to work properly...
How can u explane this?

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