Question:
i'm sure that at least some of you have read some of my posts where i mentioned my kalamazoo model 1... as well as it not being grounded properly and quite capable of administering a shock.
well, the amp has a 2 prong, non-polarized grounding prong. i'm guessing that the problem stems from the amps polarization being wrong. or could it be something else? i'm guessing that it is the polorization problem... it only shocks when one is in contact with the amp (guitar strings) and another power source (another amp, microphone, etc..)- no other times.
anyways, i thought that i would check it out with my multimeter. i plugged in my vox, plugged in my kalamazoo and plugged in cables on both of them, turned both of their volumes down, and pulled out my multimeter. i checked the ground side of the plugs for DC voltage. nothing. i checked the inner, signal carrying section. nothing. occasionally, it would show a 0.01V and then go back to 0V. so, i turned off the kalamazoo, unplugged it, flipped over the power cable and plugged it back in. i tested it again. nothing and nothing... (except the trace, occasional .01V) i then checked both AC voltage and current, still comming up with nothing. then i went ahead tested it by touching both at the same time (natually, with the same hand on both plugs, for safety reasons) and OW!
(i didn't check it by plugging it in the other way and testing both plugs... probably should've).
so, i guess my question is- there is an apparent voltage drop from one piece of equipment to the other; why can't i detect this with a meter?
Answer:
Hmmm. If you can feel the electricity, you should be able to measure it. First, just use the AC voltage range, not DC. Do not use the current measurement for a voltage potential - that is used for measuring current in a circuit, inserted in series. Putting it across a voltage potential, it will draw as much current as there is available, if there's enough it will blow its internal fuse. A lot of meters have a separate current jack for higher current measurements, like 10 amps - was it in that one? "I suspect that may have happened to your meter, and would explain why you didn't get any voltage reading. Check it - put it on the appropriate AC volt range (if its not autoranging) and try measuring something like the output of an AC power supply, or even very carefully inserting the leads into a wall socket or extension cord - but often they don't make good contact, so you may have to wiggle 'em back and forth to contact the conductor inside.
I've gotten a few ground fault shocks in my day, but its been many years. I never had one though that felt like a full 120 volts....? (I've had a few of those too ) I always wondered why. You should put a grounded plug on that amp, but that will not guarantee that you'll never get a ground fault shock. One of the main culprits is the wiring of the building - often a do-it-yourselfer has changed an outlet, and put the wires on back'rds. The only way to protect against that is to check every plug you are going to use with an outlet tester. They sell 'em at hardwre stores, maybe like 8 or 10 bux, they have lights that indicate if the outlet is wired correctly, grounded, etc.
Answer:
Originally Posted by Major Tom Hmmm. If you can feel the electricity, you should be able to measure it. First, just use the AC voltage range, not DC. Do not use the current measurement for a voltage potential - that is used for measuring current in a circuit, inserted in series. Putting it across a voltage potential, it will draw as much current as there is available, if there's enough it will blow its internal fuse. A lot of meters have a separate current jack for higher current measurements, like 10 amps - was it in that one? "I suspect that may have happened to your meter, and would explain why you didn't get any voltage reading. Check it - put it on the appropriate AC volt range (if its not autoranging) and try measuring something like the output of an AC power supply, or even very carefully inserting the leads into a wall socket or extension cord - but often they don't make good contact, so you may have to wiggle 'em back and forth to contact the conductor inside.
I've gotten a few ground fault shocks in my day, but its been many years. I never had one though that felt like a full 120 volts....? (I've had a few of those too ) I always wondered why. You should put a grounded plug on that amp, but that will not guarantee that you'll never get a ground fault shock. One of the main culprits is the wiring of the building - often a do-it-yourselfer has changed an outlet, and put the wires on back'rds. The only way to protect against that is to check every plug you are going to use with an outlet tester. They sell 'em at hardwre stores, maybe like 8 or 10 bux, they have lights that indicate if the outlet is wired correctly, grounded, etc.
ok, i'll check those... i already knew about not running an ampmeter parallel across a circuit, but that was after i had not gotten any results on either AC or DC. and actually... i think i had changed the multimeter input over to the 10A side. i know, not good practice, but i wasn't getting anything but the occasional .01V reading.
i'll have time to recheck that in a couple days.
thanks,
Tom
Answer:
I think this may be a similar issue:
I was playing my Hot Rod Deluxe at a friend's house yesterday, and it was buzzing uncharacteristically loud. I think I had the gain on about 4, and the volume on about 4. Yeah, it was pretty darn loud. But I've had it at that volume before, and never experienced the loud buzzing I had yesterday. The buzzing only occured when I wasn't touching the strings.
-Nick
Answer:
Originally Posted by Only Alive I think this may be a similar issue:
I was playing my Hot Rod Deluxe at a friend's house yesterday, and it was buzzing uncharacteristically loud. I think I had the gain on about 4, and the volume on about 4. Yeah, it was pretty darn loud. But I've had it at that volume before, and never experienced the loud buzzing I had yesterday. The buzzing only occured when I wasn't touching the strings.
-Nick
hmm... that sounds like a grounding problem with the guitar... not the amp. try a different guitar and different guitar cable. try and narrow the problem down by switching out parts to find the specific source.