RF receiver not working

[nadabro]

Hi.

I bought 3 RF receiver (434Mhz) tou use in a Arduino, but none is working (cant get any signal, pulse from it). I´ve another two receiver from different brands and they work...so its a bit strange none of the 3 receivers are working.

Looking to the 3 RF PCB i´ve noticed a bit of soldering touching a component..but in the original PCB image the soldering is not touching..here is a photo.

-The top photo is my receiver
-The bottom photo is a original photo of the receiver

**broken link removed**

Do you think that bit of soldering is causing the receiver not to work?

 

[KerimF]

And there is a missing SMD component (above D1 and D2), though it might not be too important since it is near the output.

 

[ckshivaram]

that component in the circle looks like an potentiometer to lock the vco to the required frequecny... that seems to be removed and soldered...in the first receiver... i feel that the receiver is not tuned to the frequency of the transmitter and unable to synchronise with the transmitter....

 

[nadabro]

And there is a missing SMD component (above D1 and D2), though it might not be too important since it is near the output.

Nice finding! I didint noticed the missing SMD, all three receivers are missing that SMD component. The problem is i cant get any output from D0 or D1 or D2 or D3..not even a pulse of noise, nothing.

that component in the circle looks like an potentiometer to lock the vco to the required frequecny... that seems to be removed and soldered...in the first receiver... i feel that the receiver is not tuned to the frequency of the transmitter and unable to synchronise with the transmitter....

That point of soldering is from a potentiometer which is in the front of the PCB, the other two receivers (different brand) have the same bandwidth, pretty same specifications and they work great. I tried 3 codes to see if i can get any sign of life from the receivers:

-A code to check incoming pulses, with these 3 receivers, i get 0 pulses, using the other receivers i get continous pulses (40; 20; 32; etc)
-A virtual oscillocope code, no signal with these receivers, with the other receivers i have a lot of signal, most is noise.
-My code to receive the RF packages from a device, cant get any RF package with these 3 receivers.


The datasheet of the receiver is this one
**broken link removed** (chinese)

What can i try?
Remove that bit of soldering touching the SMD component?

 

[kalyanasv]

It looks like a resistor. If it is an output resistor, then maybe you could use an off the shelf resistor looks like a 4.7M ohm (which is relatively big for an output resistor) but you might want to check on that.

Regarding the solder, it seems to be touching a capacitor, so you could potentially remove it.
But typically there are modifications made as the product evolves, so I would just call up the supplier to ask him exactly as well.