The DDT light on one channel stays on,but I can't find a reason why? What can I do?

Contact Peavey customer service for help.

is the amp working, maybe the diode is out...maybe the connection to the diode is broken...

shorted output, triac, or shorted speaker cable, shorted speaker, crossover...unhook speaker cables and see if it stops, if not, shop time.

DDT circuitry malfunction.

The amp has a failure. One side of the power amp is starting to draw excessive current to the point that the filter caps can't sustain the current so the ripple starts to be heard in the speaker. Continued use MAY burn up the speaker by sending DC through it as well as causing additional damage to circuit boards, etc..

Start out by doing some simple troubleshooting yourself. You have one working channel so substitute the cables from the working channel to the nonworking channel to see if you have a cable problem.Check to see what button settings you have on the amp. One might have been changed by accident. I am assuming your are wired up for stereo and not mono.. Here is a link to the manual if you don't have one:http://www.peavey.com/assets/literature/manuals/80300573.pdf I should also have mentioned to substitute the speakers from the nonworking side to the working side to make sure you don't have a speaker problem. Notice in the manual that it states that the DDT compression switch should be enabled at all times to protect your speakers. Also take note of page 3 Operation notes for both the thermal protection and the DDT circuits. Amplifier failure is usually caused by the failure of another component most often cables and speakers. If a dead short (broken cable or blown speaker) is presented to the amp it may fail no matter how good the protection circuitry is. If the simple tests I mentioned don't help I recommend taking it to a Peavey dealer with a good service shop as they will have access to Peaveys direct replacement parts. The schematic can be obtained but for a proper repair the direct replacement parts should be used. Peavey was one of the brands I serviced when I was still working as the service person for a music store. My eyesight has deteriorated so I am semiretired. Hope this advice helps.

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.

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.

Is the PFL button stuck down on these two channels ?

Go to http://peavey.com/support/searchmanuals/archived.cfm Their main site also has info. DDT is an active compression feature to protect the product .