diagnostic question

[KB305@aol.com]

Hey americans (16% of which are governed by someone named Bush),

My rig, containing my EDP, went weird during yesterday's gig.  I lost 
about half my gain, and all of my effects, which run between the pre-amp 
and power amp of my Mesa/Boogie.

There are a number of possibilities, ranging from a bad patch cord 
(likely) to a blown tube at V4 (half of this 12AX7A is assigned for 
'effects return').  

Here's my question: On a hunch, I checked my EDP by doing a quick loop, 
and my loop output sound was MUCH louder than what I fed into it.  So I 
dialed the wet/dry knob on my EDP all the way back to 'dry', and I had all 
kinds of volume.  It was a bit noisy, but it got me through the rest of 
the set.

What happened, and why did this work?  Shouldn't this tell me what the 
problem was with my rig?  (It's Monday, and I'm slow today...)

Kevin

PS Thanks to you all who sent me your favorable comments on 'Hello 
Dolphin'!