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Post subject: Copped a buzz
Posted: Mon Apr 28, 2014 4:37 pm
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My 69 twin has the non grounded cord which didn't bother me until today when I took it to work and flicked the stanby switch, zapping my finger.
The jolt quelled my desire to play as I wondered if I could get zapped through the guitar strings as well.
Common sense tells me the impedance is too high thru the input to worry............but should I?


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Post subject: Re: Copped a buzz
Posted: Mon Apr 28, 2014 4:51 pm
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You can definitely get zapped through your guitar. If you become the path of least resistance and the chassis is hot --- B+ will go through you instead of the tubes.

Get a three-prong outlet wire to replace the older two-prong. Be sure that the tech wires the "hot" of black lead to the fuse. This way, if the fuse pops, 120VAC will end at the fuse holder. Green grounding wire should go straight to the chassis at point of entry into the amp.

Bypass the ground switch and remove the "death cap" from the circuit.


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Post subject: Re: Copped a buzz
Posted: Tue May 06, 2014 5:18 pm
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Just curious.
Saw a utube video where a guy installs a grounded cord just as you say........but he kept the ground switch in the circuit (while also removing the death cap).
And although it makes sense to bypass the switch completely, what effect does leaving that switch in there?
He "claims" this is the right way to do it.

I presume leaving the switch in the circuit simply provides an opportunity for the switch to internally break down, causing a short.


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Post subject: Re: Copped a buzz
Posted: Tue May 06, 2014 5:27 pm
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yomamma, it makes no sense to keep the ground switch in the circuit. Because, if you use a three-prong cord, you can only plug the thing into the wall in one direction or polarity. The ground switch was used in two-prong cords that could be flipped over, changing the path of the neutral and hot leads into the amp.

Save those precious OEM switches. As they are the only ones that you can get with high voltage ratings and good quality. You can replace the original ones with a new Carling (unconnected) or a blanking plug --- for aesthetic reasons.


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Post subject: Re: Copped a buzz
Posted: Tue May 06, 2014 6:13 pm
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BMW2002Ti wrote:
Save those precious OEM switches. As they are the only ones that you can get with high voltage ratings and good quality. You can replace the original ones with a new Carling (unconnected) or a blanking plug --- for aesthetic reasons.


+1

Also, if bypassed, the now-unused polarity switch may be used for other purposes such as disabling a tremolo circuit, switching between multiple secondary taps on an output tranny, or in the case of a Princeton/Princeton Reverb, adding a standby function.

Arjay

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Post subject: Re: Copped a buzz
Posted: Sat May 10, 2014 5:53 pm
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yomammaaho wrote:
Just curious.
Saw a utube video where a guy installs a grounded cord just as you say........but he kept the ground switch in the circuit (while also removing the death cap)...


That is exactly what the drawing posted by BMW2002Ti shows. The switch is "still in the circuit" but does not do anything except that it is used for connection points. By clipping the cap, you have effectively taken out the switch, as all that the switch did was to connect the cap to one line or the other. After clipping the cap, when you switch positions on the switch, there is no cap, and nothing happens. Leaving the switch connected merely makes it easier to change the circuit to a three-prong electrical cord.

In fact, there is really no reason to change the wiring at all, simply clip the cap and connect the three-prong wiring in place of the two-prong. Leaving the fuse on the neutral wire, and leaving the power switch on the hot wire is acceptable, and much easier.

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