ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: Clyde Terry, I've checked the cord out, -- 6/30/1999 1:30 PM

Re: Shocking Twin

7/1/1999 0:03 AM
Terry	Re: Shocking Twin Hi Clyde - Mook brought up a point that I was not aware of about the warranty. If that's the case you may choose to let Fender check it out. Other than that, I've got another question or two. When you checked between your guitar and the mic, was your guitar plugged into the twin or your own amp? I assume you have the twin plugged into a standard three prong wall receptacle, right? If so, plug it in and turn the amp on with no guitar plugged in. Take a volt meter and touch to any metal part of the chassis, tip of jack, screw, whatever, and touch the other end of the meter to the round hole of the other half of the receptacle that's not being used. Now you should get zero volts. If you get a voltage reading then you have a bad ground. That way you're referencing to the same outlet and not another peice of equipment. If you have a polarity switch on the amp try that and see what happens. Is there voltage between your amp chassis and the twin? How much volts do you get between any two items? Basically if the amp is grounded properly it should not be causing the shocking. But weird things can happen. Also the speaker thing is odd, are you sure the connections at the speaker terminals and the jack are soldered properly? I've found cold solder joints at the speaker terminals before. Does the amp sound ok in general while playing? It seems strange that just touching the speaker wire makes a sound like touching the tip of a guitar cord. Just touching the insulated part without moving it around? So far the assumption has been a problem with the primary side of the power transformer. My next step would be to disconnect the wire right after the rectifiers to eliminate any problem with the B+ voltages and the output transformer, etc. Take a reading from chassis again and see if there's any voltage. It's possible that B+ may be getting to the chassis if not commonly grounded and that it is only sensed when touching something like a mic or other amp. Didn't mean to be so lengthy. Just trying to be helpful and present some ideas. Keep us posted if anything comes of it all. Keep on a truckin' Terry I know that it can be very frustrating at times in trying to solve a problem. Most of us are just guessing and making suggestions, would be much easier to diagnose in person. Sometimes the problem can be staring at you and it's overlooked until next time.

7/1/1999 0:03 AM

Terry

Re: Shocking Twin

Hi Clyde - Mook brought up a point that I was not aware of about the warranty. If that's the case you may choose to let Fender check it out. Other than that, I've got another question or two. When you checked between your guitar and the mic, was your guitar plugged into the twin or your own amp? I assume you have the twin plugged into a standard three prong wall receptacle, right? If so, plug it in and turn the amp on with no guitar plugged in. Take a volt meter and touch to any metal part of the chassis, tip of jack, screw, whatever, and touch the other end of the meter to the round hole of the other half of the receptacle that's not being used. Now you should get zero volts. If you get a voltage reading then you have a bad ground. That way you're referencing to the same outlet and not another peice of equipment. If you have a polarity switch on the amp try that and see what happens. Is there voltage between your amp chassis and the twin? How much volts do you get between any two items? Basically if the amp is grounded properly it should not be causing the shocking. But weird things can happen.

Also the speaker thing is odd, are you sure the connections at the speaker terminals and the jack are soldered properly? I've found cold solder joints at the speaker terminals before. Does the amp sound ok in general while playing? It seems strange that just touching the speaker wire makes a sound like touching the tip of a guitar cord. Just touching the insulated part without moving it around?

So far the assumption has been a problem with the primary side of the power transformer. My next step would be to disconnect the wire right after the rectifiers to eliminate any problem with the B+ voltages and the output transformer, etc. Take a reading from chassis again and see if there's any voltage. It's possible that B+ may be getting to the chassis if not commonly grounded and that it is only sensed when touching something like a mic or other amp.

Didn't mean to be so lengthy. Just trying to be helpful and present some ideas. Keep us posted if anything comes of it all. Keep on a truckin' Terry

I know that it can be very frustrating at times in trying to solve a problem. Most of us are just guessing and making suggestions, would be much easier to diagnose in person. Sometimes the problem can be staring at you and it's overlooked until next time.

Replies:

Clyde Thanks, everyone -- 7/1/1999 3:34 AM