Post by papalazarou on Oct 27, 2010 3:56:43 GMT -5
I have a question about an amp I have bought and an electric shock I got last night at rehearsal. Basically, I have an Ashdown 300w CT410-300 Combo Amp, I used it for the first time yesterday and while I was holding the guitar I touched the mic and got a bit of a shock, it was more like pins and needles than a full on - pull your hand away - shock. The guitarist has a valve amp and he was getting a similar shock on a different mic when he was holding his guitar too. I would assume the problem must come from the PA the mic's are plugged into, this is the only common denominator. Although having said that I never got a shock from the mic before using this amp. Someone has told me my amp may need grounding, but I am not sure how to go about this, I was considering taking it to a guitar tech to have them look at it and try and rectify the problem. If anyone has any suggestions I would love to hear them.
Hi papalazerou, welcome to GN2. when you touch your guitar strings, you are grounded through the lead back to the amp, and the amp is grounded, so I think thats Ok, but it means that if you get a zap from something else with a fault, it has more effect.
The fault seems like its with the PA or the room wiring, and I'd advise great caution until it is checked out. Is this a PA you usually use? and is it plugged in the same as usual?, or at a new location?. It could be a fault in the room ground wiring, so the PA is not getting a good ground connection. If you have a meter, it might be instructive to measure AC volts from microphone to guitar strings while plugged in.
Given that 2 of you got similar shocks, first thing to do (if you haven't already done so) is to get an outlet tester and check all of the outlets in your rehearsal space. Is this the same space you use all the time? Is the PA always plugged into the same outlet?
You can get an outlet tester at Radio Shack (and elsewhere) for about $10 (USD). If you're gigging, or even just practicing in different places, it's good to stick one of these in your case.
If the outlets check out OK, then the amps are the next thing, but there, I'd start with the PA first. Particularly if it's an older unit than your Ashdown. . .
Post by papalazarou on Oct 27, 2010 5:42:06 GMT -5
Hi John and Newey, thanks for the warm welcomes and replies!
It is the same rehearsal space we always use, I have just spoken with a techie I work with and he has an outlet tester which he is going to lend me (gawd bless techies! ).
One thing I didn't mention in my first post, I bought the amp 2nd hand at the weekend and the guy I bought it off didn't have the kettle lead for the amp so gave me another one, could the earthing problem be from the kettle lead? Also, is there something on the amp which is used for grounding normally? Or is it all done through the kettle lead?
Oh yeah, in answer to your point about the age of the amp vs the PA Newey, the PA seems quite new. It's hard to tell but it looks modern. My amp is an older model of the one Ashdown currently sell, it seems to have been sold til a few years ago, so I wouldn't expect there to be a grounding issue on an amp which was sold until recently.
This happened at my old practice room to a few bands.. Even though everything had been Pat tested, it was an old building (around 100 years) so we thought it must be a problem with the electrics, however it was an intermittent problem, so we never got anywhere with it