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

ampage archive

Vintage threads from the first ten years

Re: 3 prong AC plug for old Fender amp: addition

7/28/2000 3:53 AM
Bruce	Re: 3 prong AC plug for old Fender amp: addition Cool! I've never seen that happen. I've seen old-old VOX amps with the cap cracked and the grey plastic cover all split open but they still functioned. Bruce

6/20/2000 1:02 AM
Randy Jamz	Re: 3 prong AC plug for old Fender amp Well said. At least you didn't do it 'bass-ackwards' like in Weber's cheesy video! Oi Vey! Make sure you remove the ground switch while you're in there!

6/9/2000 2:14 AM
Dave K	Here is my or should I say Charles at Swamp's two cents. I like this setup and have used it on all four (bassman, twin reverb, princeton reverb, bandmaster) of my amps. So here you go. Follow the circuit from the hot on the power cord, back to the neutral on the power cord. Hot (black) goes first to the accessory socket hot, but since it's a two wire accessory socket, which one is that? It's the smaller blade opening. Ok, from there, it goes thru the FUSE. Remember, the incoming hot must be connected to the end of the fuseholder, not the ring. The ring is the output of the fuseholder, and our hot wire will then go thru the ON/OFF SWITCH. From the output of the on/off switch the hot wire will split in two directions. One connection will go to the black or in put of the transformer. The other will go to one side of a NEW CENTEROFF GROUND SWITCH. (more on this later). If the transformer has two black wires, either one will do, and the unused one will then become our return wire. That wire could be white also. The return wire will then go to the other switch connection on the ground switch, and then to the accessory socket, and finally to the white wire on the power cord (neutral). Green wire to chassis is all that's left. Lets recap the order starting with black: Black (hot) input wire, accessory socket, fuse, on/off switch ground switch AND transformer. Then, transformer return wire ground switch, accessory socket white (neutral) wire on power cord and Green wire to chassis. Lets revisit the ground switch for a moment. You really need to put a new ground switch in there too. The hot and neutral get connected to the ends and the cap gets connected to the middle. In that way, the normal position for the switch is centered. However, should you find yourself in a situation that has a two wire outlet with an adapter, you can still use the switch. Keep the ground switch AFTER the fuse, that way if the cap fails, it will blow the fuse. Folks call that cap the "death cap" but I gotta say, I've never actually seen on that failed. Could be though, so that's why it's after the fuse. Notice also that the accessory outlet is not fused. That's because we don't know how much current the accessories use! Keep is mind, the cord on the amp is an 18/3, more than adequate for even a Twin Reverb, but don't overdo it with accessories. Also remember FUSES DO NOT PROTECT THE AMP! Right. Fuses are there to protect the upstream or source of the electrical power. The idea here is that the fuse will blow, not taking the fuse or breaker in the distribution box with it. Ie, the 2.5 amp fuse will go and not the 15 or amp fuse in the wall panel. Now it could be, that if sized just right, the fuse could also protect the amp, and that's why it's sized as it is.

6/9/2000 2:14 AM

Dave K

Here is my or should I say Charles at Swamp's two cents. I like this setup and have used it on all four (bassman, twin reverb, princeton reverb, bandmaster) of my amps. So here you go.

Follow the circuit from the hot on the power cord, back to the neutral on the power cord.

Hot (black) goes first to the accessory socket hot, but since it's a two wire accessory socket, which one is that? It's the smaller blade opening. Ok, from there, it goes thru the FUSE. Remember, the incoming hot must be connected to the end of the fuseholder, not the ring. The ring is the output of the fuseholder, and our hot wire will then go thru the ON/OFF SWITCH. From the output of the on/off switch the hot wire will split in two directions. One connection will go to the black or in put of the transformer. The other will go to one side of a NEW CENTEROFF GROUND SWITCH. (more on this later). If the transformer has two black wires, either one will do, and the unused one will then become our return wire. That wire could be white also. The return wire will then go to the other switch connection on the ground switch, and then to the accessory socket, and finally to the white wire on the power cord (neutral). Green wire to chassis is all that's left.

Lets recap the order starting with black:
Black (hot) input wire, accessory socket, fuse, on/off switch ground switch AND transformer. Then, transformer return wire ground switch, accessory socket white (neutral) wire on power cord and Green wire to chassis.

Lets revisit the ground switch for a moment.

You really need to put a new ground switch in there too. The hot and neutral get connected to the ends and the cap gets connected to the middle. In that way, the normal position for the switch is centered. However, should you find yourself in a situation that has a two wire outlet with an adapter, you can still use the switch. Keep the ground switch AFTER the fuse, that way if the cap fails, it will blow the fuse.

Folks call that cap the "death cap" but I gotta say, I've never actually seen on that failed. Could be though, so that's why it's after the fuse.

Notice also that the accessory outlet is not fused. That's because we don't know how much current the accessories use! Keep is mind, the cord on the amp is an 18/3, more than adequate for even a Twin Reverb, but don't overdo it with accessories.

Also remember FUSES DO NOT PROTECT THE AMP! Right. Fuses are there to protect the upstream or source of the electrical power. The idea here is that the fuse will blow, not taking the fuse or breaker in the distribution box with it. Ie, the 2.5 amp fuse will go and not the 15 or amp fuse in the wall panel. Now it could be, that if sized just right, the fuse could also protect the amp, and that's why it's sized as it is.

6/20/2000 8:14 AM

Rick Erickson

quote:
"However, should you find yourself in a situation that has a two wire outlet with an adapter, you can still use the switch. Keep the ground switch AFTER the fuse, that way if the cap fails, it will blow the fuse."

Not if you have disconnected the safety ground by plugging into a two prong outlet.

quote:
"Also remember FUSES DO NOT PROTECT THE AMP! Right. Fuses are there to protect the upstream or source of the electrical power."

What??? A properly sized fuse will most certainly
protect power supply components such as a power transformer if another component fails & shorts. Sure there's no guarantee that having the correct fuse in your amp will keep a power transformer or any other component from blowing first, but putting in a larger than called fuse is a sure way to do more damage to an otherwise easily repairable amp. I know that's what you mean, but not everyone out here may get it.

btw Dave, I've been meaning to e-mail you since finding you're in Seattle to invite you to visit my shop sometime. Or have we already met?

6/19/2000 8:30 PM

Jim S.

quote:
"but I already have this history of getting electrocuted"

According to what I believe to be the correct meaning of "electrocution", you can experience this only once! After that, you're dead. Or did you work on tube amps in past lives?

(You're not related to Yogi Berra, by any chance? My favorite Yogi-ism is, "...ah, nobody goes to that restaurant anymore. It's too crowded!")

;-)

<<First Page

<Prev

Page 4 of 4