My signal light on peavey 2600 stays on without any input signal to the unit, what could b the cause of that ?

Take the main outputs into a stereo input (or a pair of mono inputs) on the Peavey - without knowing which Peavey I cannot tell you further info re set-up but as you'll be sending line level signal you'll need to back off the gain on the channels you input to on the Peavey

Back switches cleaning should do the job, if the two green lights show up at amp's front plate.

Swap the input cables to verify the problem stays with the same side... If it doesn't then repair the input cables or source of the audio. If it stays with the side, SUSPECT that one of the two signal wires (balanced) on the failed side has broken, probably at the input connector. Maybe bad solder where it comes in. The fact that the gain control affects the hum is GOOD as it means the problem isn't deep in the unit. Here is your schematic and service info:

http://elektrotanya.com/peavey_pv-8.5c_sch.pdf/download.html

Scroll down to the "Get Manual" link and click on it to download the manual.

Sounds like the thermal cutout is sensing over temp. Make sure there is FREE airflow around the unit. If it is in a cabinet, install vent fan(s). This amp will throw out a lot of heat. Make sure cooling fins have airflow. Cables can block the airflow... check for that possibility. Repeated thermal cycles will eventually cause failure of components.

Here is a link to the manual:http://www.peavey.com/assets/literature/manuals/00512180.pdf Page8 sections 2 through 4 discusses the LEDs. I think what you arte talking about is the DDT active LEDs. Page 12 specifically discusses this and page 15 notes that Red signifies DDT clipping. Peavey recommends that you don't defeat the DDT circuit and that is good advice as it protects your amp and your speakers. The clipping is not caused by the amp but by the amount and quality of signal being input. Check earlier in your signal chain for the cause.

You CANNOT link the outputs of the amps. They need to drive seperate speakers.

You can tie the inputs together so they will send the same sound to their seperate speakers.

Max power for the Peavey 900 is 900 Watts RMS into a 4 ohm speaker in Bridge mode... That is enough to blow many speakers.

Disconnect the speaker wiring and speaker on the bad channel. Turn the level control(s) all the way counterclockwise and turn the amp on. If your DDT (limiting) light remains lit, it's time for a visit to your nearest certified Peavey service center....G.

Chances are you have NOT got all the bad parts out yet.

HINT: While cold starting an amp after it smoked, put a 150 wat lamp in series with the power cord to act as a current limiter... saves fuses and parts.

The DDT circuits PROBABLY look for amplifier DC balance AND no overload of power supply as protection.

They COMPRESS the audio when it goes above a certain level.

SO, to troubleshoot this you will probably need an oscilloscope.

LOOK for a supersonic oscillation that you cannot hear but MAY be driving the amps beyond the DDT trip point. Drive a pure low level sine wave into the amp and follow it through to see at what point the DDT compressor senses an out of range level.

Remember it HAS worked before, and there is still a bad part in the unit. DO use my suggestion to limit the current as often while troubleshooting this type problem, the signal will suddenly go to a point to fry something, then you get to replace all the parts AGAIN.

Use the series light bulb trick when trying to first power this up. Use a 150 watt bulb in series with the 120 volt power to avoid damage and blown fuses.

check for cold solder joints from the input jacks and the fader. If any look suspicious (dull or grainy) re-solder.