Hey friends,

So I've been asked to make an attempt at fixing a, semi-broken, Holy Grail Reverb by Electro-Harmonix.

I know very little about electronics, but as of recently, I've been reading. (I ordered "electronics for dummies" the other day )

The issue:

- The pedal turns on and the signal light works.
- The 3 effects work, but there is a massive volume drop (I don't mean a bit... I mean that you can't hear the guitar at all, unless you turn a small practice amp up to full... even then it's still very quiet).
- There are no obvious things like broken solder connections.

What else could I check for?
Dude, my friend had the exact same problem with this pedal. We opened it up and it turned out a component was shorting against the side of the case, we moved it away and it started working again. Give that a try.
My equipment:
Ibanez ARX 320
Digitech Whammy IV (dry out toMusician's Gear Tuner Pedal)
GGG Rat clone
Danelectro CT-1 Tremolo
Small Stone Phaser
Boss DD-7
'01 Fender Twin
I'm probably being a total tool here,
You did check it wasn't a dead battery, right?
He probably did it before you even had to though, so..
Perhaps too much signal is going to ground?
If it worked before and suddenly stopped working, though, I'd check really carefully for broken solder joints, sometimes they're kinda hidden. And maybe the wires inside are broken, probably near where the battery goes, since that's all that's ever touched.
The first thing that I would check is that all of the wiring is solid. EH's wire is probably the worst around. Make sure one or more isn't hanging on by just a strand or two. If it were me, I would rewire the whole thing with better wire before I even started working on it. Moving things around in there is almost guaranteed to break a wire off and trying to figure out where a wire went is a real pain. Take some pictures of the wiring before you change it also. This will help you figure out where wires go if one breaks off.

Another thing to check for is a short to the enclosure like mentioned before.
Or maybe make sure you used the right power supply, or you didn't use something like a onespot, powerall, dc brick, or another switched mode power supply to power it. Most EHX pedals are near impossible to repair if you don't have a signal probe and alot of time on your hands. Unless it is something like a Big Muff or a old Octave Multiplexer, maybe a LPB-1, I'd leave it to EHX. They charge a small flatrate fee to fix it.

Or, better yet, you could get a Radical Red Reverberator, a Little Lanilei, or even a Tech 21 Boost RVB instead of that horrible EHX Holy Grail.

To the person above me, I have had nothing but positive experiences with EHX pedals as long as I take care of them. Old school Pi's are still working fine after being beaten to hell.
'89 RG-550
'92 Talman
'08 Les Paul Studio
Parkwood PW320M
Schecter Stiletto Custom 4

Fender Blues Junior
Kingston Halfstack
Blackheart Little Giant
Acoustic B20

And way too many effects.
I have nothing against EH pedals in general. I actually do like them. They just used really cheap wire in a lot of their pedals. I fix/mod pedals for a living and deal with a lot of the Small Stones, Small Clones, Muffs, etc. and almost EVERY time I open one of them up and start moving things around a wire or two or three breaks off. I also get a lot of EH pedals where someone opened it up and wires broke loose and have no idea where they went. Just wanted to warn the poster.