[Debugging] Please help me figure out why this pedal isn't working

[laserbrain]

Hello everyone, first time poster here.
I ordered a Boss GE-7 used from ebay. The description did not mention any disfunction, but when putting the pedal into my chain the pedal itself does not seem to work.
The guitar signal however goes through to the amplifier.

If I cannot find out what's wrong, the pedal will obviously get returned via ebay, but right now I'm really curious what I can do myself to fix this.

Things I've already tried:

• 9V / 12V supply. The pedal seems to be an older variation which requires 12V (see images at the end of this post)
• 9V battery (Two different ones). Other topics on the internet mention, that the battery runs a slightly different circuit than the external supply.
• Checking cables - inside the box, none of the cables seem to be loose in any way
• I did get it to light the status LED once - until I plugged in the amp to the output. That's the main reason I still have hope, but I wasn't able to reproduce this.

I have little experience in electronics (enough to get lights installed and stuff like that) and no measurement or soldering equipment available (yet - multimeter is on its way).

So for now I'd just like to see if there's anything obvious / easy to check that I can find out before getting to measure anything.

Images:

[PRR]

Welcome.

The too-obvious thing you don't say: did you stomp it? The stomp pedal cuts the EQ in or out. I don't know if there is any other indication of whether it is engaged or not.

It's probably fixable. But if you have little experience, and just bought a cord-coupler with sliders that do nothing, I think the seller has some explaining (or refunding) to do.