P-Channel mosfet turn off problem

[Sharagim]

Hi,
I am trying to use a mosfet as schematic but in benchmark this is showing 8V in "Node1" which I think should be 0V, and It can turn on a LED also. I think the schematic is ok(I got it in another post) but I am not sure why this is happening. I measured the current for BLUE LED which it is showing 30mA and I think it couldn't be the IDSS!

 

[FvM]

The shown schematic is expected to work.
Possible reasons for the observed problem:
- MOSFET defective
- wrong MOSFET pin assignment

I guess, your actual schematic has an additional signal path to turn the MOSFET on. May be it's generating an unwanted voltage across R1.

 

[Sharagim]

Exactly I have a NPN to turn it on which is working properly.
I would like to draw your attention I have this problem when I disconnect that path also.

 

[sys_eng]

what's the purpose of this circuit?

 

[Sharagim]

Remotely switch a 24V device ON/OFF

 

[Audioguru]

R1 connects the gate to the source causing the Mosfet to be turned off then the voltage at Node 1 is 0V.

 

[Sharagim]

It should be 0V but it is 8V!

 

[KlausST]

Hi,

Measure the gate voltage. Check if the output changes somehow during measurement.

Show the complete circuit. The problem most probably is not in the shown circuit.

Klaus

 

[Audioguru]

Your circuit has no value for R2 the load. Is it 22M ohms?
You talk about a blue LED but there is no blue LED in the schematic. Where was it connected?

 

[Sharagim]

I got the point from FvM and changed the supplier of the mosfet and solved.
Seems it was fake and not original.
For a test I changed the VCC to 12V and it worked ok, it shows it can't do 24V.
Then I replaced the mosfet with a new one (which I think is original) also VCC to 24V and it is working properly.