wrong DMM Led diagnostic...

[Zener_Diode]

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???

 

[Nigel Goodwin]

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???

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

 

[Zener_Diode]

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

What is O/C?
How can I check the components and to know that it works for sure?

 

[Nigel Goodwin]

What is O/C?

'Open Circuit'

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

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

 

[Tarsil]

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???

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?

 

[Zener_Diode]

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

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???

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?

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?

 

[HiTech]

Unfortunately, some components may test good under static type testing. However in the dynamic situation (under use/load) the component may act up or not work at all. This is not uncommon.

 

[HarveyH42]

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?

If you have a digital camera with a preview screen, you can see it light up that way...

 

[Tarsil]

76 Ohms!?
How about puting the LED in series with a 5V PS (could be voltage taken from the VCR), a 150 ohm res and a ampmeter. See the curent drawn by the led.
Also see https://www.gizmology.net/LEDs.htm.