Ok I was being careless with my dl4 while doing the double presets mod and I shorted something out. The lights work, the tempo LED blinks and responds however the pedal puts out hissing only. There is not even a hint of guitar signal.
On the board I can hear one of the components physically creating a screeching/hissing noise. I need help finding out what it could be. It sounds strange but I cannot figure out what is making she screeching, I have inspected it with a 1/2 pipe to my ear trying to narrow down the area but It is hard to track it down.
Here http://home.comcast.net/~aaronmacomber/dl4.jpg (http://home.comcast.net/~aaronmacomber/dl4.jpg) is a link to the general area on the board where the sound is coming from, and i have indicated the components that I have replaced.
The noise most probably comes from the PSU. It might be cause by overcurrent while the overcurrent it self could be cause by some solderbridges or something like that. Carefully check your mod and try to look for errors.
Having inspected your pic a little more I bet 5$ that the noise comes from inductor (located right from rotatory switch)