Help me to understand FL7760 IC

[Rickooo]

1 + 2 is expectable, as already explained along this thread. 3 + 4 is not expectable, there's presumedly a wiring error or defective part.

Wiring goes right. Their isn't any part damage and connection is also right. I also check from oscilloscope and multimeter. But, What I observe, while testing with a multimeter without load is:
CIRCUIT 1 & CIRCUIT 2:
-> LED- = 0 and LED +(Vo)= Vin
-> At VCC pin (which is PIN 5 of FL7760) i got 4.9 V and hence, these circuit are working fine.
In CIRCUIT 3 & CIRCUIT 4:
-> LED - = 0 to Vin (pulse) and LED + = 0 to Vin (pulse). I don't understand why.
-> At VCC pin (which is Pin 5 of FL7760) i got 0.12V and hence, this circuit is not working.

All connections are right. What do I do know. What do you think, why this happen.

--- Updated Oct 31, 2020 ---

@FvM Is there something with the IC, which it only work for current above than 1.5A?

 

[KlausST]

Hi,

When there are 4 identical circuits with different behaviour...it makes no sense to post just the schematic ... since it is identical with all 4 circuits.

We need to see the difference. And this could be done by posting photos (including error description) of all 4 circuits.
Best if we can see they in action with all wiring including power supply and DVM and LED wiring.
Maybe more than one photo per circuit is necessary.

But instead of posting many pictures of different circuits in one post I recommend to do it circuit by circuit.
Start with a pencil and draw numbers 1 to 4 on the according circuits. Front and backside.
Then start with "1". Take detailed photos of the PCB front and back.
Then connect them, power them up ant take overview / wiring photos.
Please try to post complete informations for one circuit in one post.

Klaus