[HELP] Dead Line 6 DL4

[Processaurus]

Nice work kluging the max887 chip to turn on, the only reason you'd need the eleborate turn on circuit for the max887 is if you used batteries, which would be a waste of money anyway.  I always forget that modding something is often a reasonable way to fix something that you don't need all the bells and whistles on.

If you haven't already, try the factory reset which is to hold down the two outside footswitches, and connect the power (usually it is to plug in the input, but you've disabled that, so that it's always on when there is power.

This post may interest you, may be worth checking the voltage at c40 to see if it is high enough the pedal won't think it has low batteries and sit there and flash:

Poking around for volts while going through a couple of power-ups and downs will show that the Cap (C40) needs to rise above 5.6 volts before the low battery trigger will stay off and we need this to happen immediately on power-up to avoid a brain lock. If batteries are in the device, this cap remains charged all the time and is ready. Without batteries it charges instantly when the adapter is plugged in. This is a 1000uf cap and I found I could get enough volts from the MAX660 voltage doubling cap (C59) to work, but it charges (C40) too slowly to prevent a boot lock up. I don't need (C40) and remove it. This is the point where the stomp came back to life.

[Processaurus]

by the way the two relays are for the true bypass switching, and are the latching type.  I'm pretty sure the turn on circuit using the input plug doesn't have anything to do with them.

[PerroGrande]

Well, from the schematic, it looks like the power section is responsible for a handful of voltages:

+6v
+6.6v
+3.3v
+5v
-5v

If all those are present, then the power section is probably okay (although I still don't know what actually turns it on.)
Checking that cap and going through a factory reset is a really good idea in my opinion.