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This Doesn't Seem Right


unclej
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i've got an old alamo 100w tube bass amp head. for a while now it's been acting up so i decided to check it out before i packed all my amp stuff for the move. i plugged it in..plugged in a guitar and them plugged in a jumper that i have with a 1/4" jack on one end and two alligator clips on the other..for the speaker.

being old, senile and preoccupied at the moment i plugged the speaker cable into the input jack where the cord for the guitar should go and had plugged the guitar into the speaker output jack. you can't hear anything at all when you do that by the way. :D

when i noticed what i had done i just reached down to unplug the speaker cable whic isn't insulated at the tip and shocked the crap out of myself. why would there be an output of juice at an input jack?

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I'm just reaching here, but when you don't have a proper speaker or load on the speaker output jack, doesn't that cause the power output transformer to overload and become damaged? I believe every tube amp/power amp I've ever owned has said not to turn it on without having the speaker plugged in for this reason. If that's the case, isn't it possible that the transformer overloaded and you got voltage on the input? As I said, it's just a guess and likely wrong. I'm talking outside of my area of expertise.

GBT

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I'm just reaching here, but when you don't have a proper speaker or load on the speaker output jack, doesn't that cause the power output transformer to overload and become damaged? I believe every tube amp/power amp I've ever owned has said not to turn it on without having the speaker plugged in for this reason. If that's the case, isn't it possible that the transformer overloaded and you got voltage on the input? As I said, it's just a guess and likely wrong. I'm talking outside of my area of expertise.

GBT

you're right about needing a speaker load but i only had it hooked up wrong for a few seconds and it didn't damage anything. once i changed the cords it worked perfectly. the problem had been a faulty main power switch.

so if i'm right about the amp working properly now, and it certainly seems to be, i still don't know why there would be voltage to the input jack. i've used this particular jumper on many amps and haven't been shocked before so i'm wondering if there's an underlying problem that i need to find or if it's normal.

thanks for your input.

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No, the input wouldn't have voltage on it.

The simple explanation is that maybe this old amp only has a two-prong power cord. When you plugged the amp in, it was incorrectly polarized to ground. When you tried to unplug it, you were also making contact with something that did have correct ground polarity. (Tell me you weren't standing on a damp concrete floor in your bare tootsies!!)

How's that for an explanation?

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No, the input wouldn't have voltage on it.

The simple explanation is that maybe this old amp only has a two-prong power cord. When you plugged the amp in, it was incorrectly polarized to ground. When you tried to unplug it, you were also making contact with something that did have correct ground polarity. (Tell me you weren't standing on a damp concrete floor in your bare tootsies!!)

How's that for an explanation?

joe..once again you've probably nailed it..it did have an old two prong plug and i had just replaced it when i discovered the power switch problem but i hadn't attached the ground wire at the point that it shocked me. if i was real brave i'd try it again now that it's properly grounded..naaah...ain't gonna happen. :D and no..no damp concrete.

thanks

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