Topic: Guitar pedal / adaptor polarity question

Hi all. Question for the tech heads. I think my new effects pedal may have been exposed to reverse polarity current. It seems to be working, but am not sure whether to be worried or not.

I just bought an Electro Harmonix Holy Grail Nano reverb pedal from a second hand shop. The sales bloke wanted to show me it worked and rooted around in his box of adaptors till he found one which he thought had come with the pedal. There was some confusion about its polarity and he asked his sidekick to swap the adaptor end round to change the polarity setup. It turned out to be glued on and I was a bit nonplussed to see him stick it in and turn it on anyway. The red light came on and after a second-long demo he turned it off.

Having got home with pedal and adaptor, the pedal definitely needs centre-negative and it looks as though the adaptor is set up centre-positive. I'm not 100% on this because the tip seems to have come from a different adaptor, but the "TIP" letters on one half are aligned with a little centre-positive diagram.

I've only been able to test it through a tiny practice amp which is itself on the fritz, but it's definitely producing reverb. Can't tell audio quality or consistency of sound yet.

So my questions are - assuming it did get a blast of reverse polarity, should the fact that it still works be interpreted as a bill of health? Or could stuff be damaged and waiting to die?

Also, would reverse polarity current have even produced the red light "on" signal? Does the fact that it came on mean that the adaptor is correct despite the confusing mismatch of tip and adaptor? Would it make any sense for an adaptor in a musical instrument shop to be glued into centre-positive position anyway?

heavens, it's all so confusing =]

Re: Guitar pedal / adaptor polarity question

Pretty much if it works it works but test it on a working amp so you know it works properly. Most pedals have reverse polarity protection so that'll protect them for a short amount of time with the wrong polarity.

As per the light, it shouldn't come on so yeah chances are it was the right polarity supply.

Re: Guitar pedal / adaptor polarity question

Cheers for that. Yeah, I intend to check it properly but won't have access to a decent amp till Sunday. Feel fairly reassured, though...

Re: Guitar pedal / adaptor polarity question

a one-second blast of it shouldn't cause any issues. might wanna buy an adaptor that ain't glued together though!

Re: Guitar pedal / adaptor polarity question

yeah, haven't used the adaptor he gave me - am using various spares which I can be sure of the polarity of...