I have a couple a old tube amps( Valco-Gretsch and a Hombrew) that need the 2 prong cord replaced with a Three prong. Now I am in need of advice. I know to connect the black wire of the three prong to the ground, and the white wire to the hot, or positive, but where do I put the 3rd wire-the GREEN wire of the 3 prong cord ? The old 2 prong just had 2 wires of course, balck and white. I Thank you.
Last edited by jerryjg; 02-17-2007 at 05:17 PM.
WOAH!!! SLOW DOWN!
Black is hot, white is neutral, green is ground! DO NOT HOOK BLACK TO GROUND!!!
You could kill yourself! I'm not joking!
Black is power in, white is the other side of the power circuit, and green is the ground lug. Make sure to remove the death cap, if it happens to have it...
The Green wire usually goes to the chassis ground. I put a spade terminal on it and stick it under one of the screws that holds the xfmr to the chassis. Must work, I haven't been killed yet.
VM
If aliens listened to our current top 40, they'd think that the entire planet was populated by sexually ambivalent robots with ethnic insecurity.
Bruce Collins has a good tip for this - have the green ground wire longer than the other two, so in case the ac cord gets pulled out (as could happen if someone tripped on the power cord) the hot and neutral will disconnect first leaving the amp grounded.
If you have room, you can also knot the cord inside the case so it won't pull out at all... That is, if you don't have a clamping grommet.Originally Posted by JAM
I wouldnt ever install it without a clamping grommet. An amp like Super Reverb is top heavy, they can fall forward with a great deal of force, if the cord is stuck on something it can pull out even with a grommet.
Sorry. I hit the button twice. Please delete.
Thanks for the great help! Heres a pic of one of the amps-the Valco-Gretsch. Can anyone identify a "death cap" ?I dont want to fry just yet!! Ist photo is left side, 2nd is right side. #rd photo is entire amp .
That image is WAYY to tiny to tell...Thanks for the great help! Heres a pic of one of the amps-the Valco-Gretsch. Can anyone identify a "death cap" ?I dont want to fry just yet!! Ist photo is right side, 2nd is left side.
NVM, you fixed it
Cut that thing out COMPLETELY.
Thank you so very much! I really appreciate the help with everything!!
Sure thing. The reason why I was so emphatic about the wiring is that with the black wire on the chassis, you would have 120 volts going through the ground, and through your guitar.
That's also the reason for removing that capacitor.
Yes. Thanks! Thats so crazy to hear. In my mind, black has always been negative for everything-car battery etc.,and all other 2 wire soldering i have ever done. Now here black is hot!! White is neutral and the green is chassis ground. I am stuck tho. Can anyone look at this pic. I already cut the old 2 prong cord. You can see the two grey/white wires on the power switch photo I am showing. How can I determine which side of the power switch is for the black hot and which is for the white neutral? Both of the old 2 prong wires are the same-no markings to differentiate one from the other. I am going to put green on a spade and under a Power transformer screw as suggested.
That looks like a polarity switch, so it may not matter... What I generally do is trace things down to see where ground in the circuit is going, and make neutral go on that side...
Hmm, weird... With that polarity switch, I would actually replace the switch with a DPST switch that has only one on position. If the original plug is polarized (the small prong is hot), then put the hot on towards the fuse.
You're used to DC electronics. AC wiring is a bit different, and has some interesting stuff.
Yep, in DC (cars, speakers, batteries, etc.) red=+, black=-
Could there be a death cap inside, say, a Reverb Tank or an Echoplex?
I'm asking because I don't think either has any capacitors storing any lethal voltages in them, after all, it's not an amplifier. I want to be sure though.
Is there a death cap in this circuit?
Thanks. This thing also needs a three prong plug/wire. It has a three-prong plug at the end of the original two condutor power wire. I added a temporary ground wire, but it still buzzes like hell.
I'm glad sombody knows enough about this stuff to be of help.
I just follow written instructions and pictures when it comes to electronics!
HA! You know what's funny I've been a little suspicious of that one, for different reasons. It's not actually wired that way inside the unit, it goes to the line side of the fuse. Weird, huh? Oh well, it's coming out now.
Thanks Trevorus.
Sure thing. Pretty much any capacitor that goes between a high voltage source and ground can be dangerous. Especially with no ground to the chassis at all.HA! You know what's funny I've been a little suspicious of that one, for different reasons. It's not actually wired that way inside the unit, it goes to the line side of the fuse. Weird, huh? Oh well, it's coming out now.
Thanks Trevorus.
This is a general wiring scheme for any amp that you are switching to 3-prong setup:
Always look out for a capacitor hooked between ground and hot... Bad stuff!
Found a good link about it as well:
http://tonecraftamprepair.com/html/2...ord_conve.html
Thanks for the link Trevorus, I now see I have a lot of rewiring to do before this thing is safe. I've also been looking for some guitar pick earrings, lol.
The cap in my unit is actually wired from the hot lead, on the load side of the fuse to the neutral, like this (modified drawing):
That and the hot lead doesn't even go through the fuse-the neutral does. ???
Oh well, I'm wiring it per the original diagram minus the 'death cap' when I get the time.
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