MK120 alarm always on

Kits Mini Kits Range
1

I assembled an MK120 kit and the alarm is always on. I triple checked the arrangement of all the components and I believe I put everything together correctly.

I photographed the LEDs and they aren’t lit up.

The batteries are brand new. What should I do?

Also, I read all the other threads addressing the same problem and couldn’t find a solution.

2

If the IR leds are not lit, then there is a problem with the transmitter.
Check the assembly carefully. Pay attention to soldering, component orientation and values.