After hour of playing the amp starts the effect popping sound

1. Sounds like it's the input jack., but it could be the volume knob. Have you tried turning Gain1 and Gain 2 or the Clean Channel volume? Try them first when you're plugged in to the jack on the left , then when you're plugged in the back. If none of these work, it's most likely the preamp. 2. Even if the preamp is shot, there's a quick fix - get a guitar preamp or an effects pedal - they have volume and tone controls. 3. Finally - many pros just plug into the aux jack(on the rear panel) and control the volume and tone through their instruments. Hope one of these works. Good Luck.

sounds like an electrical grounding problem

sounds like either a blown amp circuit or you simply blew out the speakers, amp circuit is most likely.

That is probably a momentary switch that is dirty and sticking. These onboard effects on guitar amps are usually nothing more than a computer sound card and I've found bad connections going to and from them as well. I do think that switch is dirty and sticking, though.

Bummer dude. Sounds like a capacitor or processor problem. Behringer stuff is really not very repairable.
I have had to scrap lots of the stuff over the years.
Great while it works and very affordable

Make sure you are using balanced lines, especially to the power amps. ALSO make sure ALL interconnected equipment is powered from the SAME receptacle or source, even if it means running extension to where the amps are powered. Ground loops are a pain and can cause serious damage to your equipment.

1) can happen if the speaker is dying - voice coil defective or magnet needs recharging. happens sometimes with low quality speakers. 
2) faulty pre-amp section can reduce overall gain resulting in lower output volume.
3) for old amps dry solders in pre-amp & power amp section can have the same effect.
4) faulty coupling and filter capacitors can severely effect frequency response too.

The bypass switch in the headphone jack is likely broken. NEVER unplug the headphones while the amp is on.

There are certain small amps that have a possibilty of popping the power amp due to a feedback arrangement. Likewise, never use the headphone jack for ANYTHING other than headphones.

Sounds like a power supply problem. Likely have to go to a repair shop unless you are electronically capable.

I would expect either a cracked board or bad solder joint is causing the problem.

Ah yes: complete catastrophe. Usually when everything is not working, it is a single reason and when that single reason is fixed, so is the amp.

Based on what you tell me, I am going to say you have a bad power tube. And I will even go as far to say that you buy a set of tubes and play on them as long as you can. If so, then you not only burned up the tube, but weakened the power section and may have a slooow tube frier. I always tell customers: modern tubes have an effective life of less that 1200 or so hours and that varies. Replace the tubes once per year if you gig with the amp: period. Otherwise, guys like me (doing repairs) stay busy and the tube companies get rich selling tubes to amps with weakened power sections.
It sounds like you burned a power tube and blew a fuse. First, you need a new set of power tubes and some extra fuses (go to Radio Shack and set the value you need in SLOW BLOW fuses).
Then, replace all the power tubes. Don't worry about biasing yet, we are just seeing if there is a problem. Next, replace the fuse.
Turn on the amp and play on it at various volumes and settings. If all is well, take the amp to a tech and get it rebiased. If you can afford it, pay to have the grid/plate and other resistors changed so the power section will be like new (clean slate with new tubes). Your amp will love you for it.
Almost all of the amps I have worked on for performance problems (cant keep tubes to stay alive for very long) are directly related to end user use. When you use a tube until it blows it ALWAYS TAKES SOMETHING WITH THE TUBE WHEN IT GOES (like the power section components). The compents will be weakened and the tubes will 'wear' at different rates that can even move them out of the 20% tolerence they must be within to sound good. 99% of the time a board repair with a retube after a catastrophe fixes the amp until the next time it is 'run into the ground'. Tube amps are NOT invinceble: they are weak compared to solid state and expensive to own. But we love tubes because they sound great. I have solid state to knock around on, when when it counts, I play only with tubes. I have spent hundreds on good tubes because you do get what you pay for.

Hope this helps!
-mike