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Author Topic: converting 2-prong to 3-prong-where does ground go?  (Read 7525 times)

rjd2

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converting 2-prong to 3-prong-where does ground go?
« on: October 03, 2006, 08:10:15 pm »

hi, im converting an ampeg b-15n power cord to 3-prong grounded plug. im sorry if this is completely obvious,but, i figure, better safe  than sorry, so...


do i solder the ground to the chassis of the amp?  if not, where to? im assuming i connect to amp chassis, but i've made an ass of myself in the past with electrical assumptions.

thanks guys.
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rj krohn

Andy Peters

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Re: converting 2-prong to 3-prong-where does ground go?
« Reply #1 on: October 04, 2006, 02:24:47 am »

rjd2 wrote on Tue, 03 October 2006 17:10

hi, im converting an ampeg b-15n power cord to 3-prong grounded plug. im sorry if this is completely obvious,but, i figure, better safe  than sorry, so...


do i solder the ground to the chassis of the amp?  if not, where to? im assuming i connect to amp chassis, but i've made an ass of myself in the past with electrical assumptions.


I have a '66 B15-N.  The first thing I did when I bought it was to replace the power cord with one that's grounded.  Attach the green ground wire to a solid chassis point.   Also: remove the ground switch, or disconnect the wires that go to it.  Remove the cap between ground and the switch, too.   Connect the black wire (hot) from the power cord to the power switch.  The other switch terminal goes to the fuse holder.  The other fuse holder terminal goes to one of the power transformer leads.  The other transformer lead connects to the power cord white wire (neutral).

-a
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rjd2

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Re: converting 2-prong to 3-prong-where does ground go?
« Reply #2 on: October 04, 2006, 10:57:15 am »

andy, thank you SO MUCH FOR YOUR HELP, i really appreciate it. im almost set, except this particular b-15n is set up slightly different:

there are two leads coming from transformer-one goes to the ground switch, another goes to the middle power switch terminal. the other(top) power switch terminal is connected to the fuse. the other fuse terminal DOES NOT go to the transformer, but to the hot wire of the power cord.

i can rewire this as you stated, but i am going to have to connect one of the transformer leads to one of the fuse leads(and move the fuse lead to the opposite power switch terminal). which transformer lead, the one that was previously connected to the ground switch, or the one that was connected to the power switch?


again, thanks a ton for the help.  this amp has quickly become one of my favorite amps for keyboards and guitar, as well as bass, of course.
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rj krohn

Andy Peters

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Re: converting 2-prong to 3-prong-where does ground go?
« Reply #3 on: October 04, 2006, 04:20:09 pm »

rjd2 wrote on Wed, 04 October 2006 07:57

there are two leads coming from transformer-one goes to the ground switch, another goes to the middle power switch terminal. the other(top) power switch terminal is connected to the fuse. the other fuse terminal DOES NOT go to the transformer, but to the hot wire of the power cord.


OK, that makes sense.  The wire that connects directly to the ground switch should also connect to one of the mains lead wires.  This is (or should be) the neutral.

The hot line goes from the other transformer lead through the switch, then to the fuse, and the other side of the fuse connects to the mains lead and should be the hot.

Quote:

i can rewire this as you stated, but i am going to have to connect one of the transformer leads to one of the fuse leads(and move the fuse lead to the opposite power switch terminal). which transformer lead, the one that was previously connected to the ground switch, or the one that was connected to the power switch?


You want to connect the mains hot (black) wire to the side of the transformer that was already fused.

I just spoke to the guy here who's in charge of ensuring that our products meet TUV and CE requirements.  He tells me his preferred connection is:

Mains hot lead to fuse.  Other side of fuse to power switch.  "On" contact of switch to transformer primary.

Mains neutral lead connects directly to the other transformer primary lead.

(Actually, preferred power switching these days means switching both hot and neutral.)

-a
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danickstr

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Re: converting 2-prong to 3-prong-where does ground go?
« Reply #4 on: October 09, 2006, 11:52:48 pm »

i usually find myself lifting grounds, as opposed to putting them on... Shocked
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Scott Helmke (Scodiddly)

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Re: converting 2-prong to 3-prong-where does ground go?
« Reply #5 on: October 26, 2006, 07:42:32 pm »

danickstr wrote on Mon, 09 October 2006 23:52

i usually find myself lifting grounds, as opposed to putting them on... Shocked


Grounding old amps is a definite improvement.  At this point I'd add some specifics, but everything important has already been covered by Andy.  Remove the "death cap", get the fuse in the right place, etc.

A properly grounded amp is almost always much easier to deal with than an amp with the original AC power wiring.  Less likely to kill you, too!
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